Author Topic: Myford 7 Carriage Handwheel Dial  (Read 7689 times)

Offline tangler

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Myford 7 Carriage Handwheel Dial
« on: February 14, 2016, 12:42:33 AM »
Hi Folks,

I have found over the years that it would be very useful to have some indication, particularly when boring, of the movement of the carriage on my Myford Super 7.  Although I have a calibrated handwheel on the end of the leadscrew, this is not very convenient to use most of the time.  Other than this, I've not really felt the need for a DRO on the lathe - fitting seems to involve some compromises in lathe functionality, particularly now that I have acquired a taper turning attachment.  However, our very own Graham Meek has designed a suitable device that was published, firstly in Engineering In Miniature magazine and repeated in his Projects for your Workshop which I bought at the Alexandra Palace model engineering show.  One turn of the carriage handwheel does not give any sensible number that allows an easy calculation for multiple turns.  Graham has devised a gearing system that gives 1 inch of travel for one turn of the dial.  This involves the use of 36DP gears - 2 x 28 T and 2 x 26 T.  The description Graham gives for manufacturing the gears involves making a single tooth cutter but as I already have a Eureka backing off device it seemed a shame not to use it to make a circular Brown & Sharpe type gear cutter.

There are various table about that give the dimensions of cutting buttons and their spacings for making gear cutters, including Don's recent spreadsheet which was published just a couple of days too late for me!  I shall use it in future, very useful.  The first job was to mill the holder for the buttons to give relief when shaving the gear cutter - easily achieved with the digital gauge.





The holes for the 2 buttons were drilled at the same angle and spaced using the DRO



The buttons were made from silver steel (drill rod) and turned to size before hardening and tempering.  The tops of the buttons were then ground on the Worden to give some rake to the cutting surface





The buttons were the fastened into the holder with Loctite retainer, as was the arm for locating in the Eureka.



The cutter blank was mounted on the arbor that will be used to hold the finished cutter- both the lathe and mill use 2MT.  The working part of the blank was reduced to the correct thickness.



The button tool was the used to bring the blank to the correct profile by controlling the depth of cut according to the calculations from the data table





The next thing I need to do was to make the tooth gullets.  I find it quicker to use my milling spindle set up for this sort of job - setting items vertically in the mill is always a bit of a faff.  The vertical slide has a fixed scale on the feed so I can easily set the milling spindle to the lathe centre height.  The spindle was the adjusted so that the leading face of a embryo tooth was on a radius.  I used my GHT HDA to divide into 12 - five turns of the handle for each tooth.





Once the blank has its gullets, it is set up on the Eureka and the "topping cutter"  is used to relieve the top surface of each tooth



After this the button cutter is used to relieve the sides of the teeth to the correct profile



The finished cutter was then heated to bright orange with a gas torch and dropped into water.  I tempered it for 15 minutes at 190C in my little heat treatment oven



Time to go to bed now - more tomorrow

Rod





Offline Don1966

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Re: Myford 7 Carriage Handwheel Dial
« Reply #1 on: February 14, 2016, 03:29:23 AM »
Hi Rod, glad to see you post this and it's really a great reference for making your own cutter. Thanks for your input on the Eureka tool and how to use it. Looking forward to more of you post on the carriage hand wheel.

'Don

Offline Bjorn_B

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Re: Myford 7 Carriage Handwheel Dial
« Reply #2 on: February 14, 2016, 08:03:22 AM »
Nice work done here Rod!

First time I have seen a eureka tool in use in a online article! Very very nice to see!

What material are you using for the cutter blank, gauge plate?

My old Heidenhahn glass scale is allso using the taper turning mountings on the back of the bed (as most dro's do). Been thinking many times how to combine a dro with a taper attachment.. No idea on how to yet..
« Last Edit: February 14, 2016, 08:06:55 AM by Bjorn_P »

Offline Graham Meek

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Re: Myford 7 Carriage Handwheel Dial
« Reply #3 on: February 14, 2016, 10:41:31 AM »
Hi Rod,

You have made a nice job of making the cutter and I look forward to following the progress on this dial. I have been experimenting with a similar form of multi-tooth cutter manufacture. It is based on the single point idea, which is really an extension of the Button technique, but using a dividing head to present each cutting edge. Not as professional as your cutter but they work well.

My best regards
Gray,

Offline tangler

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Re: Myford 7 Carriage Handwheel Dial
« Reply #4 on: February 14, 2016, 02:54:42 PM »
OMG! the boss is watching  :o.  Seriously, the design is great.  (spoiler alert) -  I have finished the item and am very pleased with the result.  Measuring the travel with a long arm dti; 1 turn of the wheel was 25.35mm.  So my dear readers know what I'm on about, here is a picture of the finished dial in-situ.



This project needs some very careful turning to size since there are several press fits involved.  The drawings are in metric units and my lathe works in imperial but I have a digital external micrometer and a metric internal micrometer so although I mostly translated the metric instructions to imperial, I tended to move over to metric measurements for the final, critical sizing.  There are 3 major components: a backplate, a spindle and the dial as well as the four gears.  Like Graham's description, I started with the dial.  I already had some suitable lumps of free cutting mild steel, though not leaded as Graham recommends.   The hole through the centre is one of those that is critical so I sized it carefully.



The outside of the dial faces the operator needs to a have a rounded profile to match the existing dials on the lathe.  Graham recommends using one tooth of a milling corner rounding  cutter but I was happy to turn a 45 degree bevel and then  use a hand graver to round the profile.





The central band is knurled.  This is too big for my caliper type knurling tool so i borrowed one of the wheels from that to make this single wheel tool.  I'm not very happy pressing a single wheel against my lathe mandrel so the result was neither very deep nor very crisp but it works fine as a finger grip and actually matches the quality of the knurling on the other dials on the lathe.



The knurling was tidied up with this "other corner" tool holder



The dial needs engraving with 100 marks.  I used my G H Thomas Headstock Dividing attachment for the division - every 36 holes on a sixty hole plate.  I used the topslide as a planer and this simple carriage stop to get each line the same length.





I the went round again and lengthened every tenth mark - every six turns of the HDA handle



I stamped the numbers on using this set up in my GHT pillar tool





That's all for now, more later






 




Offline Don1966

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Re: Myford 7 Carriage Handwheel Dial
« Reply #5 on: February 14, 2016, 03:11:46 PM »
Beautiful job on the dial Rod, you do some very nice work. Good to see some GHT'S tools in use. I always get a lot of satisfaction using them.

Don

Offline Graham Meek

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Re: Myford 7 Carriage Handwheel Dial
« Reply #6 on: February 14, 2016, 04:45:16 PM »
Hi Rod,

Thanks for the update on the dial you are a braver man than me when it comes to using a graver. My hand eye co-ordination has never been that good, one reason I chose metal turning as opposed to wood turning. Up until a few years ago when I sold the manufacturing rights, I had always made these dials in batches of 25, so anything that saves a few minutes like forming the radius with a CRC is going to grab my attention. I bet you wonder how you ever managed without the dial now.

My best regards
Gray,

Offline pgp001

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Re: Myford 7 Carriage Handwheel Dial
« Reply #7 on: February 14, 2016, 07:31:48 PM »
Hi Rod

Just looking at the gear cutter you made, it might be the way it looks in the photo, but to me it looks like the front face of each tooth does not pass through the centre line of the cutter and the cutting face is leaning back with negative rake, Normally I would expect it to be on the centre line.

This page shows what I am on about.
http://www.diametal.ch/en/product/tooling/precision-solid-carbide-gear-cutting-tools/sharpening-errors.html

Good job on manufacturing it though, but you will have to be careful when sharpening it again.

Phil

Offline tangler

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Re: Myford 7 Carriage Handwheel Dial
« Reply #8 on: February 14, 2016, 09:35:42 PM »
Thanks for the comments chaps and, Phil, you're right - I'd never noticed!  I must have put it the wrong way round in the Eureka.  Fortunately it worked, I don't suppose I will ever use it again, let alone sharpen it.

The backplate is simple turning.  A bearing is pressed into the central recess so this another hole whose dimension is critical.  The diameter was just too big for my parting tool so I had to finish off the last 1/8" with a hacksaw.





The spindle sits over the existing shaft that the handwheel is normally keyed to, so this needs a key slot in one end and a woodruff key crescent in the outboard end for the handwheel.  The inboard end is sized to be pressed into the inner ring of the ball bearing.  (The bearing is a stock item from ArcEuroTrade here in the UK).  A gear is cut onto the outer dimension.  Here I'm using a slot drill to counterbore for the screw that holds the spindle onto the carriage shaft



The standard Myford woodruff key is 1/2" diameter by 1/8" thick.  As I have a 5/8" x 1/8" woodruff cutter in my collection I used this - I made my own key anyway from 5/8" silver steel. (which reminds me, Bjorn - the cutter was made from 1 1/4" silver steel).



One end of the spindle is completed



The keyway needs slotting but first a hole is drilled for the keyway to run out into.



I've not done any slotting before so this was a new experience.  I have some 1/8" square silver steel so this seemed the correct material to use for the slotting tool - hardened and tempered.



This mechanism came with my lathe.  It seems to be based on a design shown in Len Mason's Using the Small lathe .  It worked but the tool is really rather too slender and would have been better made out of 1/8" sheet gauge plate to give more rigidity.





Time to cut the gears.  I really needed to keep the speed down to 100rpm so as not to harm the carbon steel cutter.  I put the mill belts on to the lowest ratio and the VFD was turned down to just above minimum speed.  The motor was sat for a couple of hours at very low rpm but there was no hint of the motor getting even warm - it is sometimes suggested that at very low speeds there is insufficient airflow to keep the motor cool but this did not seem to be the case.  I cut the brass gears first before cutting the 2 steel gears.







The back plate needs a few holes drilling in it.  Graham gives the XY coordinates from the centre so I had to pick up that centre to zero the DRO.  There is a clearance hole to fasten the plate to the apron, a further counterbored hole for the gear assembly spindle and a counterbore on the other face to clear the end of a shaft that protrudes from the apron.  I drilled a small through hole for this so that I could pick it up when the plate was reversed.



The 2 intermediate gears were pressed onto a bronze bush.  These in turn slide onto a steel spindle that is held by a screw on the inbaird side of the backplate.  I had to ease this with a file slightly to get the gears running smoothly.



The large brass gear is a sprung fit inside the dial, so that it can be zeroed.  Graham shows a method for slitting this with a saw but I'm afraid I just used a junior hacksaw to cut 1/3 of the way through the diameter and then a longitudinal cut before slightly springing this flap out with a screw driver.  On assembly I got a tight spot on rotation of the handwheel which I eventually chased down to one of the gears rubbing on the inner surface of the dial.  I turned a couple of thou off the inner diameter and all was fine.  Prior to final assembly I blacked the dial (and some other bits for my taper turning attachment).



After blacking I returned the dial to a mandrel to polish up the engraving.  So,  here it is again:



It really is an excellent design.  It was quite a job for me since I was working to accuracies I don't normally achieve.  There are various jigs and fixtures to make as an aid to accuracy but these are not onerous and can be made from bits and pieces in the stub end collection.  The dial runs very smoothly, you can just about hear the gears whispering away when you move the carrriage and, even more surprising, there is no wobble.  I'm very pleased with a couple of days work - it would have been so much easier to make if I already had a carriage handwheel dial!

Thanks, Gray.

Rod

« Last Edit: February 14, 2016, 09:38:57 PM by tangler »

Offline fumopuc

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Re: Myford 7 Carriage Handwheel Dial
« Reply #9 on: February 15, 2016, 06:13:50 AM »
Hi Rod, that is just impressive.
Kind Regards
Achim

Offline ths

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Re: Myford 7 Carriage Handwheel Dial
« Reply #10 on: February 15, 2016, 09:20:03 AM »
Very inspiring Rod, thanks. I have Grays book, time to get it out! Cheers, Hugh.

Offline Graham Meek

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Re: Myford 7 Carriage Handwheel Dial
« Reply #11 on: February 15, 2016, 09:22:14 AM »
Hi Rod,

Is the handwheel running any smoother now that you have fitted the dial with it's integral ball race? This is one mod that will improve the life expectancy of the poor Oilite bush. One chap years ago wanted his dial made with the backplate thicker to incorporate two bearings. A bit of an over kill but that was what he wanted, (the customer is always right).

My best regards
Gray,

Offline Allen Smithee

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Re: Myford 7 Carriage Handwheel Dial
« Reply #12 on: February 15, 2016, 11:43:52 AM »


Now that IS a handy-looking gadget! I hope you don't mind a couple of questions:

1. Is it really as simple as it looks?
2. Are those toothed pulleys and belt based on the MFA/Como items (which I had spotted a while ago as "gosh, they look good value - I must find a project that needs them!" items)
3. Is the shaft ballraced or running in plain bearings?
4. What sort of speeds do you run it at?
5. Is there anything else I need to know to copy it?

OK, so that's more than a couple, but I'm an engineer. Sticking to budgets is for lesser minds like accountants and project managers...

AS
Quidquid latine dictum sit altum sonatur

Offline vcutajar

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Re: Myford 7 Carriage Handwheel Dial
« Reply #13 on: February 15, 2016, 01:26:53 PM »
Great job Rod.  Nicely done.

Vince

Offline tangler

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Re: Myford 7 Carriage Handwheel Dial
« Reply #14 on: February 15, 2016, 05:14:25 PM »
Guys,

Thanks for the comments.

AS,

Yes , it really is as simple as it looks






The vertical slide is the Myford  non-rotating item.  The spindle is an Arrand production, ball bearing and rated up to 8000rpm.  The spindle has a 1MT and is fitted with an ER11 1MT collet.  The motor was from  http://www.ebay.co.uk/itm/ENGINEERING-MINI-LATHE-120w-YDK-CLOCKWISE-MOTOR-PEDAL-/350453897010?hash=item5198ae1732:m:mro6hZqUkLpbEINpWyyIuGg  The belt came with the motor.  The only bit I made was the bit of bent steel for mounting the motor to the vertical slide.

Sadly it seems that Arrand are now defunct.  However, I bought an ER11 parallel shank collet chuck from ArcEuroTrade recently and noticed that the shank was very accurately ground to 12.00mm.  ARC also do some 12mm i.d. angular contact bearings so I also bought a pair of these and they are a perfect stiffly sliding fit on the ER11 shank.  I'm not sure whether the shank can have a thread turned on it for applying the pre-load but it is threaded internally at the end for M6.  I'm investigating the possibilies here.

Can somebody please tell me how to hide that web address under a hypertext link?

Cheers,

Rod

Edit: - forgot to add:  No load speed of the motor is 20,000rpm, no load speed connected to the Arrand spindle is 4000. It will happily mill or drill up to 1/4" diameter in steel, when the speed drops to about 2500rpm, although this can be lessened using the foot control - which I didn't think I needed but turns out to be quite useful as a hands free on/off switch and for soft starts when drilling.
« Last Edit: February 15, 2016, 05:21:57 PM by tangler »