Author Topic: My "Learning to use a Lathe" Journal  (Read 12881 times)

Offline Brendon M

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My "Learning to use a Lathe" Journal
« on: November 12, 2016, 01:01:37 PM »
Hello again,

I thought I'd create a new thread to detail my ongoing fun and learning of the Sheraton 9" Lathe at the Connected Community Hackerspace in Melbourne, since the last thread "my first use of a lathe" was beginning to bug me with it's increasingly inaccurate title.

I have various projects on the go, but at the moment, the main two are
Tracking down the large diameter stock for the Gyroscope has been a little difficult, so I have been focusing on the pen.

After making the metal scriber (also by Clickspring), I decided to try and make a pen version. As an additional challenge, the pen needs a retraction mechanism.

I decided to base it off the twist retractable type, as can be seen in the bottom of this photo. You can see that the twistable barrel end is placed next to the second design revision.


The basic idea of my twist retraction mechanism is to use a threaded rod that has a pin that interlocks it with the pen itself so that it can't turn. Turning the outer barrel will cause the threaded rod to wind in or out, which in turn causes the ink cartridge to extend and retract... I hope that made sense.  :toilet_claw:

I attempted to make this part first, it houses the threaded rod, and the outer barrel fits over it.


I have drawn it up for the benefit of this post, otherwise I just worked from paper. Mind you, drawing this up in cad would have helped me realise just how small a part it would be.

Making this small part was not as easy as I thought it would be. I am on the second attempt, and it is still a failure^H^H^H^H^H^H^H"practice piece".

In the first attempt, I learned two things:
  • 3-jaw chucks introduce error when rechucking, significant enough to notice concentricity issues
  • Drilling out before using a thread die is a bad idea

You can see the effect of the second point - threading apparently subjects a part to a lot of stress, and I ended up accidently bending it.


After turning down the non-threaded side, I wanted to drill it out so that I would not introduce error by rechucking after threading. This ended up being a mistake. And in the end, the effect of unchucking, reversing the part and re-chucking introduced a noticable amount of error.

The obvious answer was that I needed to learn how to use a 4-jaw chuck, but initially I thought I could not do it because the 4-jaw at CCHS was unable to hold small pieces. There are a number of remedies I could have employed that did not occur to me until afterwards.

Que the second attempt. The idea was that I chuck the work piece just once, and I attempt to turn all outside diameters in one pass, to make sure the threaded and non-threaded sides were concentric. This then avoided introducing any error by rechucking.

Of course, as part of the lesson learned about threading before, I had to part off and rechuck in order to perform the threading. But how would I ensure concentricity of the drilled hole?

I spent an hour trying to drill out a larger piece of rod that would accept the part, and I would glue the part in -- basically a superglue collet that would make the 3-jaw chuck error irrelevant. This did not work because I did not have a 8.62mm drill, because I had apparently turned the outermost diameter of the part a bit less than 9mm :facepalm:

Out of curiosity, I checked to see if I could fit the part in the 4-jaw chuck. It just fit, and I decided then and there I would learn how to centre a piece on a 4-jaw. To my surprise, it was not as difficult as I thought. I would turn the part in the 4-jaw, and watch the dial indicator reach it's peak. I would then back off the nearest jaw that was opposite to the peak of ecentricity (I hope that made sense), and tighten the jaw in the direction of the ecentricity, and keep repeating this.

I managed to get the total indicated runout down to 0.03mm, or about 1.2 thousands of an inch, which I thought was good enough!

Unfortunately, after threading and drilling out, the part was still assigned to the "practice pieces" bin :facepalm: the inner and outer diameters were not concentric


It seems as though while machining the non-threaded end, it got bent. It becomes apparent in this photo:


I was holding the non-threaded end with a live centre, and I think that the pressure from the cuts has caused it to become bent?

Anyway, once again another massively long post, I hope you found this interesting. Thanks for reading :)
« Last Edit: November 12, 2016, 01:05:14 PM by brendonm »
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Offline 10KPete

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Re: My "Learning to use a Lathe" Journal
« Reply #1 on: November 12, 2016, 01:14:48 PM »
This is great stuff you're doing. There is no better teacher than hands-on. It's so easy sometimes to forget the learning experiences of almost 60 years ago and look at what a 'beginner' is doing and chuckle at the ignorance. But just a seconds thought brings back our own learning and the chuckle turns into a laugh at our own trail of scrap!

Keep it up, and keep posting. Writing about what you've done is a great teacher in itself...

And thanks for keeping this old coot grounded.....

Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline crueby

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Re: My "Learning to use a Lathe" Journal
« Reply #2 on: November 12, 2016, 02:14:34 PM »
For the large diameter stock you need for the gyroscope, a cheap place to get it could be the Drop Zone section of the website at Yarde Metals. They sell offcuts of many metals from thier commercial sales, reasonable shipping too. Sizes available vary since it is offcuts, but I can usually find what I need. Not much thin diameter stuff.

Offline Chipswitheverything

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Re: My "Learning to use a Lathe" Journal
« Reply #3 on: November 12, 2016, 06:07:00 PM »
Thanks for an excellent write up of your learning experiences ,Brendon - anyone getting to grips with using a lathe will find much to think about in your accounts of what does actually happen when you try out various methods and ideas.  The component that you are having a go at making, with it's smallish size and thin walls, is not so very simple, and you have an element of added difficulty in using a lathe that is a sort of "maid of all work" rather than your own familiar machine.

cheers, Dave

Offline Roger B

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Re: My "Learning to use a Lathe" Journal
« Reply #4 on: November 12, 2016, 06:39:47 PM »
I'm glad your posting this  :ThumbsUp:  Hands on learning is the best way and unfortunately too many people won't post what went wrong, which is the most helpful part for others who are also learning  :) I always try and post the problems as well as the successes  ::)
Best regards

Roger

Offline AOG

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Re: My "Learning to use a Lathe" Journal
« Reply #5 on: November 12, 2016, 06:49:27 PM »
Been there done that. I had the same problems with the cheap Chinese three jaw that came with my lathe. I started useing my four jaw but I hated reclocking the part in every time I had to adjust the part in the chuck. Eventually I found the joys of the collet chuck. It makes life so much easier for small diameter parts. You might want to look and see if they have one. If they don't have one and you are stuck with the four jaw, I recommend makeing a tool post DI holder. It makes things much easier. See this thread:

http://www.modelenginemaker.com/index.php/topic,5001.msg95436.html#msg95436

Tony

Offline Gas_mantle

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Re: My "Learning to use a Lathe" Journal
« Reply #6 on: November 12, 2016, 06:55:50 PM »
High Brendon

I'm a beginner myself so take what I say with a pinch of salt, but to turn the part you mention, I'd be inclined to turn and thread one end then remove it and put a piece of scrap in the chuck. Drill and tap a matching thread in the lathe and providing you don't remove the scrap from the chuck you should have a true running thread to hold your workpiece. If you support the piece with a centre and take small cuts you may be able to turn the non threaded end to size and maintain the concentricity. It should then just need  drilling through.

I can't say I've tried it but I think that's how I'd go about it and it may be worth a go  :)

Peter

Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #7 on: November 13, 2016, 01:29:24 AM »
Thank you Pete, Dave and Roger for your encouragement :)

For the large diameter stock you need for the gyroscope, a cheap place to get it could be the Drop Zone section of the website at Yarde Metals. They sell offcuts of many metals from thier commercial sales, reasonable shipping too. Sizes available vary since it is offcuts, but I can usually find what I need. Not much thin diameter stuff.

Hello crueby, you have just reminded me to update my profile with my location** - Melbourne Australia. :) Sounds like a great place, I am still yet to find a convenient place like it in Melbourne.

**Update: I have added it to my profile, but it does not want to show up under my name for some reason.

Been there done that. I had the same problems with the cheap Chinese three jaw that came with my lathe. I started useing my four jaw but I hated reclocking the part in every time I had to adjust the part in the chuck. Eventually I found the joys of the collet chuck. It makes life so much easier for small diameter parts. You might want to look and see if they have one. If they don't have one and you are stuck with the four jaw, I recommend makeing a tool post DI holder. It makes things much easier. See this thread:

http://www.modelenginemaker.com/index.php/topic,5001.msg95436.html#msg95436

Tony

Thank you Tony. As we don't have collet chucks, I will check it out that link. I am actually thinking of buying a few accessories for the lathe at CCHS, and a collet chuck set would be on that list. :)

High Brendon

I'm a beginner myself so take what I say with a pinch of salt, but to turn the part you mention, I'd be inclined to turn and thread one end then remove it and put a piece of scrap in the chuck. Drill and tap a matching thread in the lathe and providing you don't remove the scrap from the chuck you should have a true running thread to hold your workpiece. If you support the piece with a centre and take small cuts you may be able to turn the non threaded end to size and maintain the concentricity. It should then just need  drilling through.

I can't say I've tried it but I think that's how I'd go about it and it may be worth a go  :)

Peter

Thanks Peter, I had thought of this but was worried if the thread (M7 thread) would be up to the task.

One more thing I have realised I need to account for is the grip marks left behind on the outer-most diameter, highlighted here:


This is caused by the part turning in the chuck when I perform the threading (maybe I am doing something wrong, but threading takes a lot of effort!) What I should be doing is taking that cut last to remove any marking.

I've gotten over my fear of the 4-jaw chuck, so my revised strategy is
  • Chuck a 1/2inch rod
  • Turn down non-threaded side to 6mm (or should that be 1/4 of an inch, so I don't fight the lathe's native measurement system?)
  • Turn down outside diameter by 10 thou, make it concentric and also to give smooth surface for dial indicator.
  • Part off
  • Flip the part, rechuck and re-centre
  • Turn down to 7mm (fun working with Imperial Lathe and Metric thread die/taps!)
  • Do thread
  • Drill out entire part to 5mm (most nerve wracking step!)
  • chuck up a piece of scrap rod, drill out to accept 7mm thread (I need the practice for tapping a thread anyway)
  • turn down outermost diameter to 9mm, to remove tool marks

I'm going to try step 9 and 10 on a mock piece of scrap first to see what will happen to the thread. If it does fail, then a "superglue arbor" is next on my list, it's just something I've never tried.

Once again, thank you all for reading :)
« Last Edit: November 13, 2016, 01:35:01 AM by brendonm »
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Offline Chipswitheverything

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Re: My "Learning to use a Lathe" Journal
« Reply #8 on: November 13, 2016, 09:49:10 AM »
Hi Brendon, thanks for the update, and your new method will probably work out, but the drilling through while holding the 6mm dia , you have correctly identified as a potential difficulty!  Also, there still isn't a lot to hang onto earlier while exerting a lot of torque with the die threading...

 It would be possible to make this component, holding the 1/2" bar stock in the four jaw ( for added torque resistance during the threading procedure ), without removing it from the chuck until the component was completed.

 I think that if I was doing it this way, I'd chuck the 1/2" bar with about 5 mm more material length out of the chuck than the finished item.  Then turn the thread OD, and get the thread die -ed on while the beefy full dia. is holding the bar nicely.  Then turn down to the 9 mm "boss" dia.  right the way down to near the chuck jaws, and get your nice finish on the section that will remain as 9 mm.
 Then, centre drill the thread end, and open out with your 5 mm drill ( maybe in a couple of stages, 3mm or so, and then the 5 ), but just take the drilling to a depth a mil or two past the threaded length for the time being, so the 9mm section is remaining solid.
 Now, the bit that might need a trial beforehand on a bit of scrap! , and a little bit of preparation.    I would grind up ( well, I've got one! ) a stubby parting off type of tool, from a square tool bit,  (say, 1/4" or 5/16" square tool bit, doesn't need to be massive...)   - the blade perhaps 2mm wide at most, and about 8 -9 mm long, so it has a good stiffness.  The corners of the working edge could be honed with a slip stone to give a small radius, as the idea will be, not to part off with it, but to use it as a stubby turning tool, that will cut in both directions....
 Such a tool will be capable of being fed in a few thou, perhaps a bit more,  at a time, and worked sideways, to bring the 9 mm dia section between chuck and "boss" down in stages to the 6 mm dia.  And as that area of the material hasn't been drilled yet, the bar is still quite strong. If the top slide, set parallel, is used for the traverse of the tool, then you can work to a zero on the dial to preserve the shoulder length dimension.
 Then !, finally complete the drilling through the component with the 5mm drill, gently!, withdraw the drill to clear the chippings fairly often.  The drill will have a nice start in the previously drilled hole ,  -  and part or saw the thing off the parent bar.
  In fairness, there are various approaches to this sort of machining problem, and some members will say "Oh, I'd never do it that way! ", - anyone with an excellent collet set available probably would not -  but it does get the brain working to throw some idea about...!   Cheers, Dave

Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #9 on: November 14, 2016, 02:07:41 PM »
Thank you Dave,

I actually tried a variation of your suggestion on "practice piece" #2, I even ground a round nose general purpose cutter, though based on your description I did not grind the end thin enough (on that note, I should ask in my other thread how to properly grind a round nose cutter, I can't find any info on it).

It worked, but I only cut enough so that I could get a right hand cutter in to finish the job.

In the end, I still wound up with the threaded and non-threaded sides being out of alignment, I noticed this when I chucked up piece #2 in the four jaw to test Peter's (Gas_Mantle) idea of creating a threaded arbor(?) to allow me to turn down the outside diameter to 9mm. It was there I noticed the non-threaded section was spinning eccentrically compared to the threaded side. How I managed to do this is a bit of a mystery to me at the moment.

By the way, the threaded arbor did work, once tightened it the part was able to be centred with 0.01mm total runout, and the thread did not self distruct under the cutting load.

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Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #10 on: November 20, 2016, 02:23:39 PM »
Been there done that. I had the same problems with the cheap Chinese three jaw that came with my lathe. I started useing my four jaw but I hated reclocking the part in every time I had to adjust the part in the chuck. Eventually I found the joys of the collet chuck. It makes life so much easier for small diameter parts. You might want to look and see if they have one. If they don't have one and you are stuck with the four jaw, I recommend makeing a tool post DI holder. It makes things much easier. See this thread:

http://www.modelenginemaker.com/index.php/topic,5001.msg95436.html#msg95436

Tony

Hello Tony, I finally checked out your link, that is such a brilliant and simple idea, thank you :)

Also, just to clarify, my issues are more likely being caused by wear and tear, if the "Made in England" is anything to go by!



I haven't finished machining the part as of yet, but I felt I should comment on my technique of centering a 4-jaw: there are better and faster ways. See here and here for two similar approaches.

My technique, while it worked, relies a bit too much on guessing the right amount to loosen and tighten, and I could spend many minutes chasing a decent runout, which meant I spent more time mucking with the 4-jaw than machining, hence why I didn't get far on my machining.  :facepalm:

Anyway, what I did attempt to do was to true up a bit of rod stock. The unknown mild steel bar I bought from the hardware store comes factory bent and slightly eliptical. I wanted to start with accurate rod stock for ease of centering in the 4-jaw chuck.

What I would normally do is hold the other end with a tailstock while I do my machining, but I've learned that you're not supposed to hold the stock with a chuck when turning between centres; the most likely outcome is a tapered rod.

That left another technique, where you machine a bit, as close to the chuck as possible, move the piece out, re-center, cut again, re-center { repeat until happy }

Centering as close as I can... On a side note, this 4-jaw is also made in England.


One bit done


After a few repetitions...


And I'm done... finally.


So I'm definitely keen to try out those faster techniques at my next session!
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Offline Chipswitheverything

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Re: My "Learning to use a Lathe" Journal
« Reply #11 on: November 28, 2016, 01:44:33 PM »
Hi Brendon, would have sent a note earlier but for forum issues....     
    Don't worry about using ( or not using, as you have tried to do) the support of a tailstock centre for turning longer pieces of material when held in a chuck.   It's a perfectly valid method of giving rigidity to any slender barstock item.  The only proviso would be that the tailstock does need to be accurately lined with the centre line of the lathe.
  It's not all that often that true "turning between centres" happens in the workshop, and a tailstock that is "out" would render that liable to give a taper in just the same way.  On the whole, between centres turning is used for times when a component has to be removed from the lathe and replaced with certain accuracy, or turned end for end a fair amount.   Some of this technique dates back years to the days when lathes were a bit more primitive, using a modern precision lathe with good collets would mostly make the between centres method a bit redundant.
 Most lathes have a tailstock that can be "set over" for taper turning, and that also allows the centering alignment to be checked, and tweaked back to correct if there is a discrepancy.  ( Say, if someone has done some taper turning, but not restored the tailstock to centre position again  with care )  The accuracy in the vertical axis does depend on the general wear of the lathe, not so much that can be done to sort that out.
  If you have the necessary material for an item longer in length , such as the component that you have just made, chucked so that there is enough extending from the chuck, then centre drill and bring up a centre in decent condition, there's no reason why you shouldn't turn the length of it without having to muck about with the tedious re-centering and gradually extending to finish the turning operation.  The sharpness of the tool itself will help here too, honing it to a really nice edge pays dividends - it will cut effectively without deflecting the material very much.  Using something like a free cutting leaded steel, and a coolant oil also makes the task easier.

Cheers, Dave

Offline PStechPaul

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Re: My "Learning to use a Lathe" Journal
« Reply #12 on: November 29, 2016, 07:29:37 AM »
(1) You need to put your location in "Personal Text" for it to appear.  8)

(2) One way to deal with small parts may be to use a drill chuck or a min-lathe chuck, possibly held in the four-jaw chuck. The smaller chuck may provide a better grip, and possibly better concentricity. And you can still dial the four-jaw in as needed.

(3) You may also be able to make a set of soft jaws that grip evenly around a delicate thin-walled piece.

(4) It may be possible to make a collet by boring a hole the size of the part, and then cut thin slits so that the lathe chuck can apply pressure evenly.

(5) You might be able to insert a piece of stiff steel, perhaps a dowel, in the bore, and then chase the outside threads with no danger of bending or distorting the piece.

You're doing a good job with these small pieces. Thanks for sharing your experiences - many of us are amateurs and can always learn more tricks and techniques.  :ThumbsUp:

Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #13 on: December 04, 2016, 03:57:42 AM »
Hello again. My apologies in advance, this is going to be a long post. But first, I will answer some replies:

Hi Brendon, would have sent a note earlier but for forum issues....     
...
 Most lathes have a tailstock that can be "set over" for taper turning, and that also allows the centering alignment to be checked, and tweaked back to correct if there is a discrepancy.  ( Say, if someone has done some taper turning, but not restored the tailstock to centre position again  with care )  The accuracy in the vertical axis does depend on the general wear of the lathe, not so much that can be done to sort that out.
...
Cheers, Dave

On this lathe, the tailstock does not appear to be adjustable for taper turning. So for precision rods, I am probably stuck with the tedius method. An incentive perhaps for me to start with precision stock to begin with :)

That said, I was trying to do this with a 3-jaw chuck - perhaps with the 4-jaw I can probably get the rod running close to true as possible and I won't see the problems with taper that I was seeing with the 3-jaw.

(1) You need to put your location in "Personal Text" for it to appear.  8)

(2) One way to deal with small parts may be to use a drill chuck or a min-lathe chuck, possibly held in the four-jaw chuck. The smaller chuck may provide a better grip, and possibly better concentricity. And you can still dial the four-jaw in as needed.

(3) You may also be able to make a set of soft jaws that grip evenly around a delicate thin-walled piece.

(4) It may be possible to make a collet by boring a hole the size of the part, and then cut thin slits so that the lathe chuck can apply pressure evenly.

(5) You might be able to insert a piece of stiff steel, perhaps a dowel, in the bore, and then chase the outside threads with no danger of bending or distorting the piece.

You're doing a good job with these small pieces. Thanks for sharing your experiences - many of us are amateurs and can always learn more tricks and techniques.  :ThumbsUp:

It would appear a moderator has updated my profile for me, thank you to whoever that was :)

I had thought about using a drill chuck (though I was lacking a suitable means of holding it in the 4-jaw), but I decided it was time to learn how to use a 4-jaw chuck.

My recent attempt at holding the workpiece was to drill out a piece of scrap rod, tap an internal thread, and use this to hold the workpiece for the final finishing cut for the outermost diameter. This seemed to work well enough, but I still managed to stuff it up. I will get to that soon :facepalm: I reckon I will be trying your suggestion #5 for the final cuts.

First bit of good news: The lathe at CCHS has received a significant upgrade!



No more shimming the tool up to the centerline. While we only have two toolbit holders, for me it was more important to be able mount a toolbit and quickly adjust to centerline. Having a second holder means I can swap between two different toolbits quickly, but in general I only need one.



Now of course, the QCTP being purchased online means that it did not fit without a custom part being made. The original toolpost holder had a half inch bolt; the new QCTP had a bore of 16.4mm (0.6457 inches), so a sleeve was fabricated.



I did not make it. Instead, a regular member (and experienced metalworker) by the name of Rob at CCHS offered to make the sleeve, provided I supply the dimensions. As an added bonus, I got to see an experienced metalworker in action.

One thing that really impressed me was that he could convert from metric to imperial on the fly. You may recall that the Sheraton lathe is an Australian made knockoff of the Southbend 9", so all the controls are naturally imperial measurement. Not a problem for Rob; he would take measurements in millimeters, mentally subtract the remaining material to remove, and turn the cross-slide dial by the required thousands of an inch. I on the other hand, am not great at mental arithmetic. My working memory is shocking, so I need a pen and paper to keep track of previous calculations.

Furthermore, I rely more on my measurement instruments. If I am turning to a specific diameter, I will first set the digital calipers to the required dimension, and then zero. The caliper then keeps track of how much material I need to remove. This idea was borrowed from MyfordBoy.

On the other hand, CNC is considered acceptable, so I don't feel too bad on my reliance on computing machines :)

I also got shown yet another method for centering a 4-jaw chuck. Rob would wind the cross-slide in until the toolbit touched the outside diameter of the workpiece, and make a note of position on the cross-slide dial. He would then wind it back out, turn the workpiece 180 degrees, and wind the cross-slide back in again, noting the difference between the two readings. He would adjust the 4-jaw and repeat the above procedure until the cross-slide dial reads the same for both.

Again, I'd need a piece of paper to record the previous cross-slide dial reading, so I think I will stick with the dial test indicator!

And now for the bad news: I managed to muck up the part, so yet again I consign this to "trial pieces" bin. But I did take some pictures, so that's good. :)

As per my last post, I went with this plan of attack:
  • Chuck a 1/2inch rod
  • Turn down non-threaded side to 6mm (or should that be 1/4 of an inch, so I don't fight the lathe's native measurement system?)
  • Turn down outside diameter by 10 thou, make it concentric and also to give smooth surface for dial indicator.
  • Part off
  • Flip the part, rechuck and re-centre
  • Turn down to 7mm (fun working with Imperial Lathe and Metric thread die/taps!)
  • Do thread
  • Drill out entire part to 5mm (most nerve wracking step!)
  • chuck up a piece of scrap rod, drill out to accept 7mm thread (I need the practice for tapping a thread anyway)
  • turn down outermost diameter to 9mm, to remove tool marks

First up I decided to do step 9, where I drilled out and tapped a M7x1 thread in a piece of scrap rod stock -- the only part that is reusable between failures^H^H^H^H^H^H^H^Htrial pieces.



I then chucked the 9mm rod I created I created earlier in the 4-jaw. Using the centering techniques from the videos I listed in my last post, I was quickly able to get within 0.05mm runout. I probably spent a bit too much time afterwards trying to get it down to 0.01mm, but anyway practice makes perfect.

I then turned down to 7mm for the thread. Here is the finished M7x1 thread. Cutting threads is becoming less scary over time.



I then chucked up the threaded mandrel(? according to this forum, I should be saying mandrel) in the 4-jaw, and screwed the workpiece in tight to finish outside diameter, and trued up the workpiece as best as I could using the 6mm non-threaded end as the reference.

It was at this point I realised something had gone wrong. After turning on the lathe, I could see that the 6mm non-threaded side was running true, but the rest of the part was wobbling about the centerline!

I decided to true the part up in the 4-jaw using the outermost diameter as the reference. What I found is that most of the part is concentric, but the very end of the 6mm non-threaded side has a distinct wobble!

I have now realised that Step 2 should come after step 8, according to advice given here on turning thin walled parts. It had not occurred to me that drilling will produce a radial pressure, and considering the resulting wall is only 0.5mm for the non-threaded side, no wonder it keeps bending.

I continued out and turned the outermost diameter to 9mm, and I thought I'd try remove 5 thou off the 6mm non-threaded end to try and correct the wobble.

You can see here that the surface finish leaves a lot to be desired:



I think the problem here is chatter. I don't know if you can see it, but the surfaces look slightly warped, caused by an uneven cut along the length. My guess is that cutting these surfaces after drilling out has reduced the regidity of the workpiece.

Referring back to the advice earlier about turning thin walled parts, I should consider making a plug to fill the bore of the part while I turn down the outside, in order to reduce vibration. In which case, it appears I need some kind of expanding mandrel or perhaps a "superglue" mandrel for the final steps.

Sorry for the long post, and thank you for reading!
« Last Edit: December 04, 2016, 04:01:44 AM by Brendon M »
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Offline Chipswitheverything

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Re: My "Learning to use a Lathe" Journal
« Reply #14 on: December 04, 2016, 09:16:23 AM »
Hi Brendon, thanks for your well illustrated and entertaining post on the latest progress with the Sheraton lathe.  Don't worry about the length of post, nice to have an article to read over breakfast here in the UK  !
  Looking at the photo of the lathe in your post a while ago, and the link about the machines, I can see a small screw head showing at the side of the tailstock base casting.  There is probably one on the back of the base too, and these are used to push the upper part of the tailstock body a small amount sideways along a tongue and groove guide within  the castings ( once the tailstock is unlocked from the bedways ) in order to do the setting over for taper turning.  Not suggesting that you necessarily have a play with this, but if there should be an alignment discrepancy, that would be the means of tweaking the tailstock centring.  You can run a check on the centre accuracy by putting your dial indicator on a small mag base on the chuck body, and running it ( by hand !) gently round a centre in the tailstock barrel and seeing that the reading is just the same either side.

  You are experimenting with an assortment of turning techniques that will give a good repertoire for other components that "turn up" !   Looking back to my comments about machining this particular small threaded sleeve ( Nov 13th ), when I suggested a way of leaving the item on its parent bar throughout the sequence of operations, I'm still inclined to favour adopting that approach.
 In general, as can be seen in a lot of the illustrations of machining processes here and there on this forum, keeping the component for as long as feasible on its "stalk" as you might say, can be more helpful than separating it and then having to devise ways of hanging on to a small scrap that is getting a bit fragile to clamp and secure.
 The smaller the component, and the more delicate the sections or walls ( and what you are presently making does come into that category, with the drilling through ), the more helpful it can be to think of making it on the end of a parent chunk, and cutting it free at the latest point possible.  When turning, it makes the concentricity problems much easier to solve.
  Though it's not in the lathe, the two pictures of the crosshead for my beam engine, still on a piece of 1/2" bar when mostly machined,, give an idea of what I'm getting at...
Cheers, Dave

Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #15 on: December 07, 2016, 12:23:19 AM »
Thank's Dave, I will give your suggestion another go.

This post was supposed to detail my victory and how I completed this part, alas I did not. By the time I had some food, and ground a new round nose cutter, and trialed the new cutter on a piece of scrap, it was almost time to go home.

And also, the latest and last video in the Clickspring series had came out, so we all gathered around at CCHS and watched it :)

In which case I decided to work on something completely different, and much easier: a sleeve bearing for my hand powered coffee grinder. Silly designers did not support the grinder shaft at the bottom, so on courser grind settings, the whole grinder was able to wobble about, producing a very inconsistent grind. Luckily, I had a lathe I could use to fix that  :Lol:
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Offline Jo

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Re: My "Learning to use a Lathe" Journal
« Reply #16 on: December 07, 2016, 09:53:14 AM »
And also, the latest and last video in the Clickspring series had came out, so we all gathered around at CCHS and watched it :)

:o I nearly missed that. Thanks for reminding me. 

Jo
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Offline Chipswitheverything

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Re: My "Learning to use a Lathe" Journal
« Reply #17 on: December 07, 2016, 12:19:13 PM »
Hi Brendon, that doesn't sound like a bad afternoon to me!  Especially as I've just now got a workshop with the machines all covered up in blankets against the chilly and damp December air, not very useable in there...
  Just to pick up on a point that you mentioned earlier, it's IMHO a much better practice to jot down your workshop calculations as they arise, as you are doing. In fact, I don't personally know any model engineers who don't do just that, whether their mental arithmetic is good or bad. It's so easy to make a slip up, or plain forget,  - phone call, interruption -   and if something doesn't seem quite right, how are you going to look back for a check on what you did?  Just strike a line through the calculation as it's done with, so you know that's the old one...!     Dave

Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #18 on: December 17, 2016, 11:17:40 AM »
Thank you for the reassurance, Dave :)


OK, this will likely be another long post. This long post does have a happy ending, however!

In an attempt to get this part finished, I went to CCHS on Monday, Tuesday and Wednesday.

On Monday, I decided to tackle the step of slotting the part, mostly to see how I can do it, but also to get some practice on a scrap "practice piece" and address anything that might go wrong. So sometimes there is a benefit to mucking up parts.

The chosen approach was to mount a rotary tool onto the cross-slide. This actually worked pretty well, although on the next attempt, I will mount it 180 degrees so that the wheel is spinning anti-clockwise and thus the grit sprays downwards instead of upwards.



The part was held in the chuck using the only piece that has trascended the scrap pile: the threaded mandrel I created earlier.



This procedure went a lot easier than I was expecting. Here is the part now slotted.



The grinding disc cut a slot just wide enough to fit this pin perfectly.



Now why am I slotting it? The next part to produce is a 5mm rod that is threaded on the end, and has a pin. This pin sits in the slot and prevents the pin from rotating. Thus, when a nut is turned on the threaded rod, it will move the threaded rod back and forth.

Here is an image of that part that I will be constructing next.



So, with that out of the way, it was time to re-attempt "Trial Part IV: A New Hope". I decided to retry Dave's suggestion of performing all possible turning operations before parting off, so that I would spend less time re-centering in the 4-jaw chuck.

All the main dimensions that could be done with the RH tool were turned down. I then checked with the Test Dial Indicator to see if the very end had any runout. It was less than 0.01mm so I considered that good enough.



I proceeded to cut the thread with a M7x1 die (not shown). After cutting the thread, I checked with the Test Dial Indicator to see if I had somehow caused the part to bend. All was good, so I moved onto the next step.

For the non-threaded side, this meant that I would need a round nose cutter. After viewing this image of a round nose cutter, I realised the radius that I had previously ground was too big. I took this time to review all the tool bits I had ground, and found all the rake and relief angles far too aggressive, so they were all reground.

You can actually see the difference in surface finish on the non-threaded side and the outer-most diameter:



The LH cutter was reground back to sensible angles, and the cutting was so much better. Once again, I got out the Test Dial Indicator and checked to see if I had bent the part during the LH cuts. All was good! I should mention that I decided to make the non-threaded side 7mm instead of 6mm, in order to ensure good rigidity for the final drilling operation.

I took this time to regrind my RH cutter too, and turned the outer-most dimension to 9mm.



Once again, the difference in surface finish was much improved. I can't believe I didn't pick up on this problem earlier :facepalm: I once again checked with the Test Dial Indicator, and once again all was good!

I also discovered another reason for performing the turning operations this way. You may recall that I created a threaded mandrel to hold the part for finishing the outer-most diameter. The RH cutter tends to produce a lip of metal in the direction of cut, which then requires an application of the LH cutter to remove. So in the end, I would have still required some way to hold the part on the non-threaded side to remove that lip.

Now that I think about it, I should have turned the whole lot down to 9mm and then done the cutting of the 7mm non-threaded side.

Anyway, I got on the with drilling operation, also the most nerve wracking operation to perform.



I am probably starting to sound like a broken record, but I rechecked for wobble with the Test Dial Indicator, which showed that all was good. If I was going to mess up the part again, I wanted to know which step was causing it. This is my machining equivilent of "step-debugging" programming code :D

Here is a picture of the parting off:




At this point, I was almost shouting "Woohoo!", until I remembered that this has taken me four attempts. (D'oh!).



I've said it before and I should take my own advice: no cutting with blunt or badly ground tool bits!

After a bit of deburring, which I learned I can use a tap instead of a large drill bit for a better finish, the exit and entry holes appears to be concentric with the outside diameters. I am also able to pass the 5mm ink cartridge through the part without binding.



So in conclusion, in producing this part I have learned the following:
  • Incorrectly ground tool bits - in all cases, wobble (due to chatter) and poor surface finish was due to this
  • 3-jaw chucks are not repeatable - not a problem if you can avoid parting off until late, but otherwise use a 4-jaw
  • Try to delay parting off for as long as possible - but don't try to machine too far out or you could bend the part
  • Maybe don't try and produce 0.5mm walled parts, unless there's a good reason
  • Using a chuck for turning between centers is OK, as long as the part as running as true as possible, and the tailstock ways are not considerably worn

I still have to slot this part, but usually I have stuffed up before I get to this point, so I have made progress!

Thanks for reading :)
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Offline Chipswitheverything

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Re: My "Learning to use a Lathe" Journal
« Reply #19 on: December 17, 2016, 09:18:26 PM »
Hi Brendon, great stuff!, and I admire your persistence in giving the awkward little component another go.
 Very pleased that you found the suggestions about making the component in one continuous process, remaining in the chuck throughout, to be a help.   It does often solve a few problems if you can scheme out a way of not having to remove or re-chuck an item.

Cheers, Dave

Online MJM460

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Re: My "Learning to use a Lathe" Journal
« Reply #20 on: December 18, 2016, 11:48:05 AM »
Well done Brendon.  It might seem to have taken a few false starts, but when you consider how much of the work on a lathe consists purely of the operations you have completed so far, centring the stock, turning to diameter with left or right shoulders, drilling, threading, parting off and you have included machining a slot as a bonus.  Now to try boring, then practice, which of course never ceases.  It is a lifelong pursuit.  You will learn to improve accuracy, and surface finish, and you will gain experience with different materials.  And as the need arises in your future projects you will continue to learn many other techniques which further increase the versatility of the lathe.  The many interesting posts and fabulous build logs by the experts on this site will keep inspiring you as to what is possible.   But you are now up and running.

MJM
The more I learn, the more I find that I still have to learn!

Offline Mosey

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Re: My "Learning to use a Lathe" Journal
« Reply #21 on: December 18, 2016, 04:48:15 PM »
A good book of fundamental machining I have found helpful is "

Machining Fundamentals: From Basic to Advanced Techniques"
by John R. Walker
Amazon has it used for $2.00 + shipping.
It covers most of the techniques you would want for some time, and is clearly illustrated.
Mosey

Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #22 on: December 19, 2016, 11:54:19 PM »
Thank you Dave and MJM for your words of encouragement :)

Also thank you Mosey, I shall check that book out.

I am going to finish the part tonight by cutting the slot, after that it's time to do the pin.

*edit: hundredth post!
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Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #23 on: March 19, 2017, 09:41:54 AM »
Wow, 3 months since the last post.

On my pen project I got stuck on - of all things - cutting an M5 thread. I think the die might be blunt, but then again I could just be incompetent. I am going to purchase my own tap and die set, but of course a good set is over a hundred dollars and right now I need to be spending my money on other things. Blasphemy, I know!

So I decided to have a go at Clickspring's Benchtop Gyroscope, for something different. At the very least I'd practice on a bit of aluminium bar that was laying around the hackerspace.

Now the plan calls for 3 inch brass rod stock but I only could find 2.5 inch brass rod. And in this "prototyping" session, I also only have 2.5 inch aluminium bar, so that will have to do.

First up was cutting off a roughly 1 inch chunk... with a hacksaw. Because I thought, how hard could it be?


An hour later, I swore to myself (lots of swearing actually) that I'd much rather a mechanised cutting process! It wasn't just that it took me about an hour to get through the 2.5 inch alum bar, but I also cut on a angle


The angle of cut translated to quite a bit of time and wasted stock facing on the lathe


Now I also don't have layout blue, but I found that using a cutter to scribe lines into the part worked well enough. I picked my target inner and outer radii, and computed the necessary movements of the cross-slide in thou.


I'm only loosely following the plans in terms of looks rather than dimensions. The video talks of scaling up or down but in this case I'm just copying the look of Clickspring's design.


I made a few mistakes during this session which luckily could be corrected
  • While removing the bulk of the metal in the recess I nearly cut too close to the target lines. I would not have been able to form the tapers if I'd cut any closer
  • While cutting the tapers, I forgot to rotate the toolpost back into position so that the toolbit was perpendicular to the flywheel again. This meant that I was effectively plunging the tool into the stock (at an angle), producing a bad finish. Thankfully I figured out my idiot mistake that there was enough material to correct.

And just one last thing to mention, this was my first time cutting aluminium, and it just flies off the tool in long streams! Compared to brass and steel, this was making a giant mess.


Next week, I will cut the other side, and outside using a so called "superglue arbor". Thanks for reading! :)
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Offline steamer

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Re: My "Learning to use a Lathe" Journal
« Reply #24 on: March 19, 2017, 10:17:33 AM »
Great stuff Brandon!    There appears to be a burr on the face of your flywheel there.  Make sure you take that off before you try tp glue it to a glue chuck.

When the time comes....let us know, and we can talk you through the glue chuck....it's not hard....just need to pay attention to some points is all

 :ThumbsUp: :ThumbsUp: :ThumbsUp: :ThumbsUp:

Dave
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Damned ijjit!

Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #25 on: March 19, 2017, 10:30:34 AM »
Thanks Dave, it could be a burr, but it could also be my dodgey camera work ;D the shot seemed to come out slightly blurry no matter what I did, but I'll double check that the surface is free of burrs.
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Online MJM460

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Re: My "Learning to use a Lathe" Journal
« Reply #26 on: March 24, 2017, 03:40:17 AM »
Hi Brendon,

Good to see more good progress.  Sharp tools are always the issue in community spaces, so the area in which you start to build your own collection.  They will come in handy when you eventually get your own machinery.

In my experience the time taken and angular cut indicate the the blade was blunt - you could have cut steel in that time.  I suggest the first addition to your private tool box be some good hacksaw blades.

I suggest you visit that well known green warehouse and buy yourself an assortment of good blades.  Get one each of 18, 24 and 32 tpi. And try them out, generally the coarse one for large soft stock like your aluminium, fine for thin rods and sheets.  Only buy the best quality on the shelf.  I like the white ones, and have now bought packets of 10.
Use a blue felt tip maker for layout until you get some proper blue, it is quite adequate for most purposes.  Then wrap a piece of paper around the bar, when the straight edge lenses up is is perfectly square and your felt tip, half on the paper will give you a good line to follow.  A wide blue line will also give your scribed lines good contrast.  Clamp a 3/4 square length of pine so the rubbing the saw on th timber keeps it on the line use a few drops of oil on the blade and you will get a much better cut.  The wood will guide many cuts before it it better to discard it and use a new one.  I usually have to waste only about 1 mm to face it up in the lathe or mill, and I do not have that much more experience than you.  I suspect the experts around here do much better.

And eventually, perhaps for Christmas get yourself a set of taps and dies for threading.  Only buy hss.  I have found the set a bit over $100 from the red and blue warehouse very satisfactory and has lasted for years (many threads in all metals, only just starting to replace the sizes I use most).  The cheaper alloy steel ones will soon be blunt, and are only good for the odd sizes they sometimes contain like your M7x1 which you might never use again as it is difficult to buy nuts in that size, but not included in the hss set.

MJM460
The more I learn, the more I find that I still have to learn!

Offline Ian S C

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Re: My "Learning to use a Lathe" Journal
« Reply #27 on: March 24, 2017, 11:15:38 AM »
Brendon, as taps and dies go, it's best that you buy best quality HSS, but rather than buying a full set, get the ones you are using, maybe a taper tap and plug tap, you don't need all three.
Ian S C

Offline Chipswitheverything

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Re: My "Learning to use a Lathe" Journal
« Reply #28 on: March 24, 2017, 01:21:36 PM »
Hi Brendon, good to see that you are back in action on the lathe after the break.  As you have found, some aluminium swarf from turning can be difficult stuff, and it can be dangerous too, the long streamers of cuttings can bird-nest up around the tool and job:   and of course the stuff is like cheese wire as far as fingers are concerned. A tool with a chip breaker ground in, or a carbide insert that has one already formed, can be helpful.  But for safety, stop the lathe entirely when the swarf builds up, and clear it away from the work/tool bit  area using pliers or some metal implement to yank it away.     Dave

Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #29 on: March 25, 2017, 10:02:56 AM »
Thank you MJM460. The hackerspace has a cold cut off saw I can use, but I'll give the hacksaw a go again. The cut off saw went through the aluminium OK but I had to nurse it a fair bit, and I have doubts about going through 2.5 inch brass.

... I have found the set a bit over $100 from the red and blue warehouse very satisfactory and has lasted for years (many threads in all metals, only just starting to replace the sizes I use most).

and

Brendon, as taps and dies go, it's best that you buy best quality HSS, but rather than buying a full set, get the ones you are using, maybe a taper tap and plug tap, you don't need all three.
Ian S C

I think I understood MJM's "red and blue" warehouse reference. I saw that they had a HSS tap and die set but but they are not split. Are split dies better?

I was originally thinking of getting a set from Sutton tools, but now looking at those again, they don't seem to be HSS.

Hi Brendon, good to see that you are back in action on the lathe after the break.  As you have found, some aluminium swarf from turning can be difficult stuff, and it can be dangerous too, the long streamers of cuttings can bird-nest up around the tool and job:   and of course the stuff is like cheese wire as far as fingers are concerned. A tool with a chip breaker ground in, or a carbide insert that has one already formed, can be helpful.  But for safety, stop the lathe entirely when the swarf builds up, and clear it away from the work/tool bit  area using pliers or some metal implement to yank it away.     Dave

Thank you Dave. My first time cutting aluminium and I wasn't used to the swarf building up around the tool bit. Without thinking I used pliers to clear away the swarf without stopping the lathe, to which I was later informed is dangerous behaviour. Thank you also for pointing this out.  :facepalm:


On that note, I didn't get anything further done this week because the lathe gear head needs to be topped up with oil before I can start using it again. Hoping to have that sorted next week.
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Online MJM460

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Re: My "Learning to use a Lathe" Journal
« Reply #30 on: March 31, 2017, 10:16:19 AM »

Hi Brendon,

It is worth trying again with new hacksaw blades, though the cut off saw obviously saves time and elbow grease when one is available.  I cut quite thick steel by hand as I do not have access to an alternative, also no more room in the shop.

The hss tap and die set I mentioned (you have the right one) I have found to be very good.

The dies are not split like most, but are more interesting than that.

They are labelled g6 which is a standard tolerance grade that matches h6 taps.  Such a tolerance cannot be maintained with a split die which enables the user to adjust to a satisfactory but unknown fit.

The taps are also different.  They are marked with 1 groove on the shank, two grooves and plain, being first cut, second cut and final cut.  This is unlike the more common taper intermediate and bottom with which as Ian says you can get away with having two, which should include the bottom tap for blind holes.

The difference?  I can assure you that each of the three taps makes an approximately equal depth of cut.  You need to start with the first cut which as a longer tapered lead in to start the threads and make turning the second cut easier.  You will not be able to fit a commercial nut on after the second cut even after running the full length of the available teeth through the hole and you must follow with the final cut for final size and which is only a real bottom cut in the larger sizes.  I have had to grind the bottom point of some of the smaller ones to get deep enough into blind holes.  The cutting torque is great enough to be in real danger of breaking a tooth if you try and go straight to the final cut.

You can buy separate sets of three taps for one size and separate dies to replace the ones you eventually blunted, from the same place, but my experience is you will not need them until the original price is long forgotten.  The price for single size sets is such that the full set is better value if you need four or more sizes.  If the quality is still as good as the ones I purchased, the set is good value.  Of course it is difficult to tell, and quality from the big warehouses can vary, but they have been continuously available for many years so I assume they are always good sellers and there will be feedback if they change specification.  I hope I don't sound too much like a salesman, I am just relating my experience as a customer.

I believe the Sutton and Goliath hss tools are also exceptionally good and I have some of those for sizes smaller than the smallest in the set, and for a constant 1 mm pitch set I have accumulated for M8, M10 and M12 where the standard ISO Coarse seem a bit coarse for model making purposes.  Still not as fine as the ME 32 tip and 40 tip series, but seems to work well.  The ones available from tool suppliers seem to be the more usual taper, intermediate and bottom sizing.  I still need to buy a small number of ME sizes so I can use the commercial tails and nuts for tubing I use for my steam engines as the price makes them not worth making manually.

MJM460
The more I learn, the more I find that I still have to learn!

Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #31 on: April 03, 2017, 01:33:58 PM »
Hello MJM, thank you for replying. I have only now just worked out how to switch on thread notifications, hopefully I will appear more responsive.

On that note, Christmas has come early  ;D I picked up a new set of whitewall tyres at Springvale, and decided since I was only 15 minutes away, I went to visit the red and blue warehouse. Wow, so many lathes and milling machines! Long story short, I purchased the hss tap and die set. I got to try the M5 die and cut a thread without any difficulty. So I guess I am not simply incompetent  :)
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Offline Roger B

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Re: My "Learning to use a Lathe" Journal
« Reply #32 on: April 13, 2017, 08:04:25 PM »
Glad to see you are still at it  :ThumbsUp:  :ThumbsUp: You have probably heard/read that you should always release the tension on a hacksaw when you have finished using it. If you don't the frame distorts resulting in a wandering cut.
Best regards

Roger

Offline Admiral_dk

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Re: My "Learning to use a Lathe" Journal
« Reply #33 on: April 13, 2017, 09:02:21 PM »
Quote
You have probably heard/read that you should always release the tension on a hacksaw when you have finished using it. If you don't the frame distorts resulting in a wandering cut.

Actually no, never, not even at Technical School ....  :thinking:

But I very well adware of this being true on old "frame saws" made from wood to cut wood - and much to my dismay, all mine are gone, my sister threw them all away when she helped my father preparing his house for sale  :'(

Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #34 on: April 14, 2017, 12:42:02 PM »
Ah yes, the old "sister throwing my stuff away" story :( unfortunately I can relate.

I have actually finished machining the flywheel on my gyroscope project, I just have not had time to upload the photos. I am visiting my family and will be heading out bush for the weekend.

To summarise though, the superglue arbor/chuck worked really well, and drilling out the six holes using a milling attachment worked ok, but it makes me long for a rotary table :)

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Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #35 on: April 20, 2017, 09:13:38 AM »
Hello, I am finally getting around to the most important thing in this forum: pictures!

I'll try to keep the amount of description to a minimum

This is my first time using a so-called "Superglue Arbor".

Of note here was my difficulty in cutting the face. In the video, the face is cut by starting near the center and working outwards, but due to my tool bit grind angles, I was having trouble clearing the spigot that was being formed, so I instead reduced the outside diameter a bit at a time.

Also, my tool bit angles were not allowing me to cut into the corner. I instead plunge in a few thou and create a countersink to work around that.



Some channels to ensure that there is enough air for the glue



And it's set! It literally takes only half a minute to bond solidly.



So I turned down the outside diameter just enough to clean up the surface. By co-incidence, I'd managed to reduce to the actual 2.5 inch diameter.



And then I cut the recess. First whoops moment: forgot to measure the other side's recess depth so that at least both sides are consistent!



Next up is drilling the 6 equispaced holes. Now up to this point I'd tried a myriad of ways to index using the lathe chuck (trying to count the number of pulley teeth per chuck revolution etc), until I decided to try mounting the lot in a milling attachment, to give me both x and y movement. Mercifully, the milling attachment dial was also in thousands of an inch.



Using the plain ol' "Mark 1 Eyeball" to find the horizontal "zero". Setting the centerline height took me ages too, but I got pretty close.



A picture of the overall setup, ready to go.



Obviously, cutting the first two holes wasn't too big a deal



And here is my crude answer to the "repeatability" problem of the 3 jaw chuck: I got sick of having to re-align the drill bit (to minimise runout) every time I swapped it back in.



All 6 holes are drilled... And unfortunately there is an error with the top two. It seems I miscounted the number of turns (about 20, since the Y axis dial only goes to 50 thou!)



Oh well, that's why this is the "test piece"... Still, I love how well the Superglue Arbor works. A bit of heat from a big blow torch and it comes apart no problem.



And here is the finished "prototype"



What I've learned is: I want a rotary table I can mount to the lathe! D'oh!

Thanks for reading :)
« Last Edit: April 20, 2017, 09:50:40 AM by Brendon M »
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Offline deltatango

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Re: My "Learning to use a Lathe" Journal
« Reply #36 on: April 20, 2017, 09:54:17 AM »
The finish on the prototype wheel looks very good! I think you've learned a lot more than just the need for a rotary table.  :)

This thread has prompted me to look up Clickspring - great stuff there. Thanks for the introduction.

Cheers, DT
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Offline Gas_mantle

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Re: My "Learning to use a Lathe" Journal
« Reply #37 on: April 20, 2017, 10:04:56 AM »
Hi Brendon

This reminds me very much of the same problems I was facing a couple of yrs ago when trying to make my first flywheels.

I found to get 60o spacing for the radial holes a simple way was to put a spirit level on one jaw of the 3 jaw chuck holding the work then scribe a horizontal line across the entire diameter using a scribing block. Rotate the chuck 120o and level the next jaw to scribe the next line etc.

It's not super accurate but good enough to give an even spacing to the eye on smallish wheels.

Peter.

Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #38 on: April 20, 2017, 12:05:35 PM »
In this case I was aiming for accuracy: first, to get an idea of how difficult being accurate is. Second, to minimise vibration since this is part of a gyroscope.

I was initially going to simply mark out each point, but then I thought about how much runout the small drillpress has, coupled with accurately centering the drill over the point... I thought perhaps this was a good time to learn how to use the milling attachment.
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Offline gerritv

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Re: My "Learning to use a Lathe" Journal
« Reply #39 on: April 20, 2017, 01:48:16 PM »
If you count the teeth on the gear on LH end of your spindle you can use that to index the work in chuck. Mark each of the 6 holes,(spot drill works great for this)  then move work to the milling slide for drilling.

Gerrit
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Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #40 on: April 20, 2017, 10:43:12 PM »
Hello Gerrit, this was one of the things I tried, although in this case I was counting the pulley teeth on the drive. Sadly, no combination of gears* got me a number divisible by 6.

*note: this Sheraton lathe has a gear head with 4 possible speeds.
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Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #41 on: April 26, 2017, 01:13:43 AM »
Finally found a metal merchant selling offcuts of various stuff that I can easily get to on the way to work. I was able to get a three inch aluminium pipe to build the gyroscope's frame. Naturally,  the process of drilling the two holes for the bearings is proving to be fun.

But otherwise, this project is nearing completion :) I will put up more photos soon.
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Offline mklotz

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Re: My "Learning to use a Lathe" Journal
« Reply #42 on: April 26, 2017, 03:38:52 PM »
Another way to lay out six holes on a flywheel is to take a piece of hex stock and turn a tenon to fit the central hole in the flywheel.  Loctite or superglue it in place and use it as a locator in the mill vise to orient the wheel.  After the holes are drilled, unglue the wheel with heat.
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Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #43 on: April 27, 2017, 08:10:27 AM »
Thanks for that tip, Marv. That would work really well in my case.
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Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #44 on: May 04, 2017, 10:52:10 AM »
Hello again, I am pleased to announce that I have managed to finish my gyroscope project. Once again, this project is based on plans by Clickspring Projects.

As stated in an earlier post, I finally found a metal merchant which had the stock needed to finish this project. I will attempt to summarise the rest of the build, since a better explanation exists in the form of this video series by clickspring.

I made the gyroscope frame from this piece of 3 inch aluminium pipe



First the faces were cleaned up. I then used a pipe center finder to scribe a line.



I did not have access to a mill, so the next step of drilling the bearing holes required a bit of thought.

At first I tried to hold the piece so that the pipe face was horizontal, in order to use the tailstock and spot drill to align the work. Unfortunately I've misplaced the image.

But I found it difficult to secure the piece, especially without bending it. So I tried clamping it like so and just hoped that it would be square enough.



But I found that I could not really ensure both sides would be level. Also, drilling like this meant it wanted to rotate out of alignment.



I then thought back to the video and the drilling is taking place from the top. So I changed the arrangement to match, however now I could not use the other mark to line things up. I just hoped for the best.



Clickspring does explain in this article here that the cone bearings are able to tolerate some misalignment, so I tried my best not to worry too much.

Ok, so with the holes drilled, I then "deviated" from the original plan again* by tapping both holes. (*note: totally NOT by accident). You see here my crude attempt to ensure that the tapping will be as parallel as possible.



With both holes tapped, I moved onto cleaning up the frame:



Unfortunately, a slight disaster struck while parting off:



I'm not sure what happened but the tool "bit in" about halfway through, pulling the work piece off the chuck. It might have been because I had the piece turning at 60rpm? I rechucked the frame and just parted off again to the left a bit. All this ultimately meant was a bit more to clean up.



It's not perfect, but it would do for the "prototype".



Next were the cone bearings. This was pretty straight forward so I will only show a completed one:



A shout out to my new tap and die kit, which made short work of the aluminium and brass.

Finally, I needed to cut the 60* tapers on the spindle. Unfortunately, the 4-jaw chuck was unable to grip the 1/4 inch rod. After a while of contemplating solutions, and given that it was 11pm and a 1 hour drive home, I decided throw accuracy to the wind and use the 3-jaw chuck, and see just how bad .2mm runout would be.

The answer is that there is indeed vibration, but it still works!

I have a video of it in action which can be viewed at the following url: Gyroscope video (32mb)

Here are the completed pictures:





I must say, it is incredibly rewarding to make something really neat like this gryoscope project, for the first time. I can't wait to finally get my first engine running.

Thanks for reading! :)
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Offline steam guy willy

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Re: My "Learning to use a Lathe" Journal
« Reply #45 on: May 04, 2017, 01:38:50 PM »
Another way to lay out six holes on a flywheel is to take a piece of hex stock and turn a tenon to fit the central hole in the flywheel.  Loctite or superglue it in place and use it as a locator in the mill vise to orient the wheel.  After the holes are drilled, unglue the wheel with heat.

To mark out the six holes i always use the three jaw chuck jaws as datum points and use the cross slide to scratch the datum points . then remove from the chuck and centre pop then proceed from there......I have a piece of steel to insert between the lathe bed and each chuck jaw in turn.....

Online Kim

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Re: My "Learning to use a Lathe" Journal
« Reply #46 on: May 04, 2017, 08:36:02 PM »
That is a pretty cool little Gyroscope!
Completely agree - there's nothing like the feeling of making something like this with your own hands and seeing it work!
Kim

Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #47 on: May 05, 2017, 12:37:18 AM »
Thanks Kim, its a great learning project too. And it also makes a great ornament on my desk at work. Certainly a conversation starter!

I look forward to remaking the flywheel with brass, and I have a few ideas how to tackle the problem of gripping the small diameter rod in the 6 inch 4-jaw chuck
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Offline Roger B

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Re: My "Learning to use a Lathe" Journal
« Reply #48 on: May 08, 2017, 09:04:35 AM »
Excellent  :praise2: Finishing something that works is always a good feeling  :wine1:
Best regards

Roger

Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #49 on: May 15, 2017, 07:13:01 AM »
Thank you Roger!

I think after tackling a few miscellaneous jobs, I will start thinking about a simple stirling engine.

On the cards:
  • Finish that pen project
  • Repair my shimano nexus 8 speed hub
  • Convert my hand powered coffee grinder to electric powered

The last one is certainly going to be the most entertaining. Eventually the electric motor may be replaced by something else!
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Offline Brendon M

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Re: My "Learning to use a Lathe" Journal
« Reply #50 on: May 25, 2017, 11:51:28 AM »
Hello again, short post this time

I managed to correct the spindle accuracy by using a custom "holder". The holder was made using a piece of drilled out bar, and then hacksawed in half. The hacksawing was not accurate in any way, but as long as I assembled the two halves in the same direction, it had no problem holding the 1/4 inch rod in the 6 inch 4 jaw chuck.



And then I was able to get the runout to 0.01mm. After recutting the tapers, the spindle spun freely in the bearings!

Unfortunately, the gyroscope still has a vibration, caused by the fact that the 6 holes were not all drilled equidistant  :facepalm: only way to fix that is to remake the whole flywheel again.
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