Author Topic: Micro lathe refurb  (Read 22769 times)

Offline tangler

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Micro lathe refurb
« on: August 24, 2014, 03:17:23 PM »
 Making helical gears for the Wyvern involved a complicated and accurate set up on the Myford.  Breaking this down in order to turn a new blankto replace the one I'd just botched (several times  >:( ) convinced me that a second lathe would be useful.  Lack of space and using Jo's Cowells at Guildford has led me to look for a micro sized lathe (it's not entirely your fault Jo).

This one turned up on ebay. 









It's a middle period Flexispeed with back gear for good speed range, has the fine feed but no change gears for screw turning.  I can't imagine that I would want to cut gears on a lathe this size, the Myford can do that but it would be good for stud and bolt making with die cut threads.  Pick was reasonably local and the clincher was the fact that it came with a 4 jaw chuck of the correct small size for this lathe.  I already have 2 small watchmakers self centring 3 jaws with inside and outside jaws respectively.

It is quite crudely put together, most surfaces seem to have been prepared with a rather coarse grindstone but the design and iron castings are sound.  The spindle is mild steel in the cast iron journals and although there is some wear, there is sufficient adjustment in the split.  It will do for the time being.  The slides though need some attention. 
« Last Edit: August 24, 2014, 06:10:35 PM by tangler »

Offline Jo

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Re: Micro lathe refurb
« Reply #1 on: August 24, 2014, 03:55:07 PM »
(it's not entirely your fault Jo).

:mischief:

One cannot have too many lathes  ;)

Jo
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Offline Dave Otto

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Re: Micro lathe refurb
« Reply #2 on: August 24, 2014, 04:02:04 PM »
Looks like a fun little refurb project.


Dave

Offline tangler

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Re: Micro lathe refurb
« Reply #3 on: August 24, 2014, 04:06:33 PM »
I've not really done much scraping before so this will be a learning experience.  I bought a far eastern scraper some time ago but have singularly failed to get any sort of edge on it to cut cast iron - I suspect it needs re-hardening.  I have a small random assortment of tungsten carbide tips so I put this scraper together:



It's not an ideal shape, I think more curve would be better but it seemed to work OK.  You can also see my surface plate in the picture.  This is planed but not ground.  However, I can't feel the ridges with my finger tips and a DTI registers no peaks or troughs.  Pictures of the scraping will be a bit thin on the ground - there was a lot of blue about which I was reluctant to get all over the camera.

The first task was to get the top of the bed flat.  After about 3 hours I managed this, there was a distinct hump in the middle which I could feel as a tight spot when traversing the saddle.



Next I flattened the nearside V which is the surface that the non gib side of the saddle rubs against.  I have a pair of machined parallels which are 1 x 3/4 x 9".  After testing with blue on the surface plate I found a good edge to use as a straight edge.  (Surprisingly good actually, I could almost lift up the plate with the parallel with a bit of blue between them - well, that's what it felt like anyway).  Another 3 hours or so and I had this:



I found the whole operation pleasantly satisfying, just had to remember not to keep rubbing my nose with blue fingers.

The next operation was to bring the outer V parallel with the inner.  This set up showed that there was a taper of about 0.006" over the length of the bed.  That's a lot of scraping :o . I decided to mill this off.

So, first I set the lathe bed  down on the parallels and machined the feet.



Then turned the bed over and used a dovetail cutter.  The forces are not really working in my favour here - you can see  the chatter marks which aren't quite as bad as they look, it's about 0.0005" between peaks and troughs



The dovetail cutter wasn't quite big enough to give the full depth so I had to remove the ridge with a file.  Alternating between the DTI and the straight edge I manged to get the 2 Vs parallel within 0.0005".



The little saddle was a rather more difficult prospect to scrape and I elected to just touch this up with the dovetail mill







The contact area was much improved (although the blue is a bit thick in this photo)

The headstock is fastened to the bed with 1 screw and a locating peg.  Having put the headstock back on the bed I tested for top to bottom parallelism.  I have a length of 1/2" ground mild steel which fits the journals perfectly.  Unfortunately, rotating showed it to be bent.  A length of Silver steel (drill rod) though was fine.  Surprisingly, top to bottom alignment seemed to be perfect. 








« Last Edit: August 24, 2014, 06:11:58 PM by tangler »

Offline tangler

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Re: Micro lathe refurb
« Reply #4 on: August 24, 2014, 05:21:27 PM »
Side to side alignment is controlled by the headstock pivoting on the pin and a slotted screw holding it in location.  I'm not really happy that this is a long lasting solution so elected to line everything up with the indicator



Clamp in position



and the drill through 1/4" for a roll pin




Disaster  :(  It slipped somewhere in the process. and is 0.02" out of alignment.  Plan B:  Remove the pin and drill out and tap 1/4" BSW as for the original screw and use cap head screws in both holes.  The headstock holes were drilled oversize to allow a little play.  Replacing the original screw means I can tighten it up using an allen key with the test spindle in place.



If that doesn't stay put I'll try putting some horizontal screws in (a la Myford) to bear on the rearward screw which will provide a more positive adjustment than hitting it with a hammer and also lock the rotation.

Offline tangler

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Re: Micro lathe refurb
« Reply #5 on: August 24, 2014, 05:34:05 PM »
The tailstock was not drilled through which I find a bit surprising since you can't use a knockout bar to remove the tooling.  It's a deep hole and very fortunately I have a 9/64" drill brazed to a rod that's left over from my bagpipe making attempt.  So I drilled as deep as I could with conventional drills and finished off with the special.  I can now use a 1/8" knock out bar.



The tailstock barrel had suffered some damage where the barrel rotation preventing stud had broken away.  JBWeld to the rescue!  I have one piece of PTFE which fortuitously is 1/2" OD.  Nothing sticks to PTFE (well it will but you have to etch with Hydrofluoric Acid)









I also made a couple of better looking hand screws for manipulating the tailstock



That's all for now.  Thanks for looking

Rod

Offline Roger B

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Re: Micro lathe refurb
« Reply #6 on: August 24, 2014, 05:39:10 PM »
That's a nice little machine and some good refurbishment  :ThumbsUp:  :ThumbsUp:
Best regards

Roger

Offline smfr

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Re: Micro lathe refurb
« Reply #7 on: August 24, 2014, 05:46:12 PM »
That's a lot of work there, Rod. This should be a very handy little lathe when she's up and running.  :ThumbsUp:

Simon

Offline ths

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Re: Micro lathe refurb
« Reply #8 on: August 24, 2014, 09:43:24 PM »
Nice work there Rod, very impressive work with the scraper, good tailstock mods.
Mine has the screwcutting and dogclutch, and it occurred to me to leave it set up at some useful thread (like 32 or 40 tpi), as the Myford has no gear box (and changing from slow self act is a pain).
I must take some photos, as it came from a deceased estate with every known Flexispeed accessory.
Looking forward to more.

Cheers, Hugh.

Offline John Hill

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Re: Micro lathe refurb
« Reply #9 on: August 24, 2014, 10:08:15 PM »
Very nice work Rod, it made me go out and take another look at mine. 

I was really impressed when mine arrived as it seemed to be so much more like a 'real lathe' than my little Adept lathe.

Hugh, I would like to see those photographs,  I got the original (I think) layshaft with mine which I understand is uncommon.

Here is mine after a cosmetic refurbishment.

Flexispeed lathe blue by MrJohnHill, on Flickr

Rod, if you dont mind, I will copy a couple of those enhancements you made to the tailstock.
« Last Edit: August 24, 2014, 10:12:35 PM by John Hill »

Offline tangler

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Re: Micro lathe refurb
« Reply #10 on: August 24, 2014, 11:18:11 PM »
Thanks for the interest guys.

Any mods I've made have been copied from somewhere else - nothing patented  :).  I haven't yet decided on the speed range either.  As it will be used for fairly small diameter stuff I really think it should go up to at least 2000 rpm, the bearings should stand it with adequate lubrication.  I'm still pondering what motor to use, I'd like to keep the whole package as compact as possible.  I've got a fairly small 1/6 HP induction motor that would do but I also have a brushed motor that I could use with a pwm speed controller but it's a bit noisy.  I could also try my 120w sewing machine motor.  The 1/4 induction motor that came with it is too much and anyway needs a pull on the belt to get it to go under load.  Any advice or pics greatly appreciated.

Cheers,

Rod

Offline tangler

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Re: Micro lathe refurb
« Reply #11 on: August 31, 2014, 12:43:24 AM »
I've been painting the castings.  While the spindle is out I've taken the opportunity to make a couple of fittings for the nose.  I bought 2 SC chucks from ebay, one with external and one with internal jaws, one of which came without a backplate.

Having found a suitable lump of steel, I drilled and then turned it to 1/2" BSF tapping size.



I then part turned the thread before finishing off with a tap, which is supported by a pump centre.





I then turned the  1/2" register



And tried the spindle for size



The spindle is 1/2" diameter through the bearings so I was able to mount it in a collet



Having parted off the backplate this was then screwed on to the nose for finishing,



and turned the register so that the intermediate plate from the chuck is a snug fit





The intermediate plate was used as jig for drilling and then tapping the mounting holes



I also wanted to make a chuck to use my ER25 collets.  I managed to find a big enough lump of unidentified steel.



I supported one end with a centre



Before skimming off the  outer skin - I think this was originally black hot rolled



I parted off to length, keeping the centre in until the diameter of the parting bridge was about 3/16"



Impressive coils from the Q cut parting tool, using power cross feed and at a good speed (800?) rpm



I turned this down to a suitable diameter for the register OD before reversing the job and mounting and clocking up in the four jaw independent

The ER screw thread is 32 x 1.5 mm.  My imperial Myford Super 7 lathe has a gearbox.  I used a method to cut metric gears that has been popularised by John Stevenson but was first mentioned (as far as I can tell) by The Rev. David Hoskin in Vol 171, issue 3955 of Model Engineer.  It involves substituting the 24 tooth spindle gear with a 34 tooth gear and then selecting 24 tpi on the gearbox to give a pitch of 1.499mm.





The ER half angle is 8 degrees so I set the angle up on the topslide using the Myford ER collet chuck



The first attempt at checking the angle with some blue was spot on  :o





I transferred the job to the Flexispeed spindle to make the final cut



Here is the selection of chucks,  I've cleaned up the 4 jaw and I had to make a key for it as well.  I was a bit worried that the ER25 chuck might be a bit lumpy for the little Flexispeed but it doesn't look out of place with the other chucks.



Cheers,

Rod






Offline Jo

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Re: Micro lathe refurb
« Reply #12 on: August 31, 2014, 01:32:01 AM »
 :naughty: This is being kitted out very nicely Rod.

Jo
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Offline Ramon

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Re: Micro lathe refurb
« Reply #13 on: August 31, 2014, 09:17:53 AM »
That's some nice work going on there Rod :ThumbsUp: that'll be a very nice little asset once done.

Love the build up work with the JBW by the way - that's one for the 'uses' file  ;) It will be interesting to see how well that stands up over the long term.

Regards - Ramon
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Offline ths

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Re: Micro lathe refurb
« Reply #14 on: August 31, 2014, 01:21:24 PM »
That is looking great Rod, and if you don't object, would you mind if I put up a photo or two of what I've got for my Flexi? I don't want to hijack the thread.

Cheers, Hugh.