cross slide micrometer wheel

[Robin teslarParticipant @robinteslar]

Hi My Fordians (ML7s)

If I won the lottery, then I'd have two sets of machines in a warm workshop Imp/Metric. Thats not going to happen

A lot of my work comes in metric designs and of course my trusty old ML7 is in glorious imperial fettle. We all know what rubbish the stand cross slide micro wheel is. I always use a dial gauge, but I was used to a proper micrometer wheel on my work Harrison. So I looked at what the usual vendors offer and its £25 for a replacement metric wheel, in fact you can pay nearly £100 for a replacement lead screw/nut assembly.

It seemed to me that it should be within the purview of the average hobbyist to make his own conversion wheel. Its a matter of matching the wheel diameter vs leadscrew tral to correspond to an exact number of wheel graduations and make up a collar to fit over the existing handwheel.

How to make the graduations, well I have got a full ML7 dividing head but the seems overkill and probably take me all week to get it set up.

So I thought I would make the collar out of a suitable blank, attach a paper printed scale around the circumference then put protective perspex cover over that, then I thought I would go for gold and make two scales (on different diameters IMP and MET)

Has anyone else tried this?

Any tips to speed up the design process, much appreciated and I am happy to share my design results if successful.

Cheers

Robin

[Robin teslarParticipant @robinteslar]

change to metric

[John BromleyParticipant @johnbromley78794]

I don't think the diameter of the wheel is going to make a difference, one revolution of the hand wheel will move the slide the same amount as dictated by the feed screw. I'm not a Myford owner but if its a 8tpi screw for example the travel will be 3.175mm for each revolution.

John

Edited By John Bromley on 06/11/2014 16:58:17

Edited By John Bromley on 06/11/2014 16:58:48

[frank brownParticipant @frankbrown22225]

How about clamping on a digital vernier and selecting metric. Sort of like a poorman's DRO – then write an article for MEW.

Frank

[Robin teslarParticipant @robinteslar]

Agreed JB, the slide movement will be the same, but its how it is represented on the circumference of the wheel.

Divide by PI gives a diameter ratio of 1.105, So we want 3.175 to fit on a diameter which gives say 100 convenient divisions, the factor is 1/3.175 = 0.3149. So a 94.49 mm circumference wheel gives a diameter of 30.07mm

So print a strip 94.49mm long and divide into 100 should give increments of 0.3mm per division, actually more convenient to divide by 2 and express as a reduction in diameter when turning as we normally do with a cross slide

This is just off the back of an envelope and I need to play around with the factors and diameters a bit more to get say .025mm and 400 divs/rev

equiv to ca 1 thou per division

I can print this out on CAD and stick is to the wheel, then punch grads through the paper onto the wheel, its not rocket science, Ive got the AL billet ends sorted and can make one for each slide and maybe one for the leadscrew handwheel

Hope you get the idea and the collar can fit right over the existing wheel

Robin

[Robin teslarParticipant @robinteslar]

Posted by frank brown on 06/11/2014 18:04:44:

How about clamping on a digital vernier and selecting metric. Sort of like a poorman's DRO – then write an article for MEW.

Frank

Hi FB

I think this approach has already been well covered on here. These cheap digital calipers can make a cheap DRO but they are not very reliable, fragile and dont always hold their original zero reference correctly especially after powering down automatically as they do. From expereince, I dont trust them for continuous work. The old fashioned mechanical clock gauge is far better (provided it runs smoothly and hasnt been abused – like allowing it to spring back too quickly

[JasonBModerator @jasonb]

Does not sound too accurate to me, say you want to feed the tool in 9mm. That would be 300 of your 0.3mm increments but you will actually have moved the tool 9.525mm. Think thats too much of an error for my liking.

You say you use a dial gauge at the moment, why not get a 50mm travel metric dial gauge, they are cheap enough. Just mount whichever you need for teh job in hand

[JasonBModerator @jasonb]

Actually easiest option is to base it on metric thread cutting.

127division on the wheel would each be 0.025mm

But still not easy to do the 9mm as it would need two full turns and 106 divisions

[CotswoldsPhilParticipant @cotswoldsphil]

Here is my version of a DRO fixed to my Super 7 which was originally made for an ML7. It gives me repeatable accuracy to 0.0005 or or 0.01mm at the push of a button. Just keep cutting fluid out of it, hence the plastic cover – don't ask. Total cost £35 + some bits from the cum-in-for box.

 

Phil

 

 

Edited By CotswoldsPhil on 06/11/2014 18:54:57

[Jon GibbsParticipant @jongibbs59756]

Hi Robin,

My ML7 came with a cheap vertical milling slide with a 12 TPI thread on it and no scale.

I turned a conveniently sized cylindrical collar (1.044" diameter) and made a paper scale with 83.333 1mm divisions around the circumference (= 83.3333 mm).

I glued the scale on with PVA and put some shellac varnish over the top (doesn't cause the type to run) and it does the job but it doesn't get a lot of handling.

Tubalcain2 has made some neat new ones for his Logan lathe recently which may give you some better more robust dials.

Hope this helps

Jon

[Robin teslarParticipant @robinteslar]

Posted by JasonB on 06/11/2014 18:24:47:

Does not sound too accurate to me, say you want to feed the tool in 9mm. That would be 300 of your 0.3mm increments but you will actually have moved the tool 9.525mm. Think thats too much of an error for my liking.

You say you use a dial gauge at the moment, why not get a 50mm travel metric dial gauge, they are cheap enough. Just mount whichever you need for teh job in hand

I am afraid you are taking me too literally at the moment, I want to check my own ML7 tomorrow and come up with a proper design with say 254 increments/rev, so that gives about .025 mm/div on diameter. Its all about scaling

and that would give .1mm for a major div (multiplied by 4). A 50mm dia collar would give div spacing of 2.48 mm. But I'll have another think about it , too cold out there now

Robin

[Robin teslarParticipant @robinteslar]

Posted by Jon Gibbs on 06/11/2014 19:51:05:

Hi Robin,

My ML7 came with a cheap vertical milling slide with a 12 TPI thread on it and no scale.

I turned a conveniently sized cylindrical collar (1.044" diameter) and made a paper scale with 83.333 1mm divisions around the circumference (= 83.3333 mm).

I glued the scale on with PVA and put some shellac varnish over the top (doesn't cause the type to run) and it does the job but it doesn't get a lot of handling.

Tubalcain2 has made some neat new ones for his Logan lathe recently which may give you some better more robust dials.

Well thats the idea, I am not completely barking

Its just that I was trained on manual controls and had confidence in dial read offs.

Whilst I appreciate the possibilities of the cheap DRO on CP's pic, I am just wary from my experience with a digital caliper using same technology. Presumably CP, does your DRO power off when static? Of course professional ones dont do that and have a proper (vulnerable) power lead – all at a price. For the money they do provide remarkable accuracy so long as you dont lose the zero

Robin

Hope this helps

Jon

[Michael GilliganParticipant @michaelgilligan61133]

Robin,

In the spirit of your opening post … I think the link I posted in this previous thread might be helpful.

MichaelG.

Edited By Michael Gilligan on 06/11/2014 21:21:23

[Enough!Participant @enough]

Posted by Robin teslar on 06/11/2014 18:13:04:

 

Divide by PI gives a diameter ratio of 1.105, So we want 3.175 to fit on a diameter which gives say 100 convenient divisions, the factor is 1/3.175 = 0.3149. So a 94.49 mm circumference wheel gives a diameter of 30.07mm

So print a strip 94.49mm long and divide into 100 should give increments of 0.3mm per division, actually more convenient to divide by 2 and express as a reduction in diameter when turning as we normally do with a cross slide

Shouldn't that be .03 mm/div … or more accurately .03175 mm/div …. (3.175/100)? Seems like a pretty gross approximation to me and not particularly useful. Better to work with the machine's native units I would think.

[In practice, the top/cross-slides on the ML7 are 10 tpi  so 2.54 mm/rev]

Granted the production dial is pretty schlokky (what were the real Myford Company thinking of). I found some nice dials from LMS – spare parts for a mini-lathe or mill I think – with 50, very legible, divisions which give 2 thou/div on my ML7 (easily interpolated to .001" ). Easy enough to adapt for the Ml7. I imagine Arc et al would sell similar over there.

For metric dimensions I just convert what I'm aiming for (one conversion) then work in inches.

(edit to remove stupid inadvertent smiley …. again)

 

Edited By Bandersnatch on 06/11/2014 22:23:04

[Robin teslarParticipant @robinteslar]

Posted by Bandersnatch on 06/11/2014 22:18:34:

Posted by Robin teslar on 06/11/2014 18:13:04:

Divide by PI gives a diameter ratio of 1.105, So we want 3.175 to fit on a diameter which gives say 100 convenient divisions, the factor is 1/3.175 = 0.3149. So a 94.49 mm circumference wheel gives a diameter of 30.07mm

So print a strip 94.49mm long and divide into 100 should give increments of 0.3mm per division, actually more convenient to divide by 2 and express as a reduction in diameter when turning as we normally do with a cross slide

Shouldn't that be .03 mm/div … or more accurately .03175 mm/div …. (3.175/100)? Seems like a pretty gross approximation to me and not particularly useful. Better to work with the machine's native units I would think.

[In practice, the top/cross-slides on the ML7 are 10 tpi so 2.54 mm/rev]

Granted the production dial is pretty schlokky (what were the real Myford Company thinking of). I found some nice dials from LMS – spare parts for a mini-lathe or mill I think – with 50, very legible, divisions which give 2 thou/div on my ML7 (easily interpolated to .001" ). Easy enough to adapt for the Ml7. I imagine Arc et al would sell similar over there.

For metric dimensions I just convert what I'm aiming for (one conversion) then work in inches.

(edit to remove stupid inadvertent smiley …. again)

Edited By Bandersnatch on 06/11/2014 22:23:04

Yes quite right B

In fact its just dawned on me that you will never get a full 360 out of the scale. You will be limited to say 250 divs

but it will be accurate as .25mm/div but in fact I want the scale to read diametrically rather than radially, so I dont have to keep dividing by 2 so maybe I can make a scale for 0.1mm on diameter. I'll do a dwg for the scale on 50mm diameter dial tomorrow and post it.

Robin

[Robin teslarParticipant @robinteslar]

B

do you means this dial from RGD

http://www.ebay.co.uk/itm/RDGTOOLS-ORIGINAL-SHERLINE-LATHE-CROSS-SLIDE-DIAL-just-one-cross-slide-dial-/291083097218?pt=UK_Home_Garden_PowerTools_SM&hash=item43c5e79482

Robin

[Enough!Participant @enough]

Posted by Robin teslar on 07/11/2014 00:12:57:

do you means this dial from RGD

No, this was the one I used from LMS along with this spring and the rest of the adaptation was straightforward enough.

[Robin teslarParticipant @robinteslar]

well here's my attempt at the metric scale .01mm scale, i cant seem to attach a dwg so a jpg has to suffice. Its intended to fit on a 50mm wheel

somethings slipped in the jpg and I could fix it but it shows the method

At either end there will be a blank area not intended for use, but you can get +/- 1.2mm

Robin

[JasonBModerator @jasonb]

So are you saying the scale will only be used for less than one rev worth of measurement, seems very limiting.

Still think the 50mm travel dial gauge would be more practical and just like what you are using at the moment.

[Robin teslarParticipant @robinteslar]

Posted by JasonB on 07/11/2014 07:31:46:

So are you saying the scale will only be used for less than one rev worth of measurement, seems very limiting.

Still think the 50mm travel dial gauge would be more practical and just like what you are using at the moment.

Yes thats true <1 rev BUT when you are turning down a diameter towards the last few cuts then you re-zero the dial each time so its not really that limiting. I also realised that Ive got the scale upside down and I also need to divide by 2 to give a diametric read out rather than straight radial. More work needed

I think I might as well make a dual scale for IMP/Met diametric readout

Yes the dial gauge is essential also but doesnt divide by 2 (although I think Ive seen a DRO that does? cant remember where)

I have a battered Mitutuyo which readsout to 5places absurd accuracy but it was only a fiver on Ebay

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 07/11/2014 07:31:46:

… Still think the 50mm travel dial gauge would be more practical …

.

Agreed 100%

But if you are feeling masochistic, you might produce a geared conversion wheel. … I have some for a much larger machine that [if memory serves me well] have 125 and 127 tooth gears internally cut, which mesh with a common pinion. [some devious tolerancing going-on there, methinks]

Very tricky to do at Myford scale … Go for the Dial Gauge !!

MichaelG.

.

Edit: Here is a similar [not identical] arrangement to the one I mentioned, nicely described and illustrated.

Edited By Michael Gilligan on 07/11/2014 08:46:37

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Robin teslar on 07/11/2014 08:20:50:

BUT when you are turning down a diameter towards the last few cuts then you re-zero the dial each time so its not really that limiting.

.

Robin,

… if I understand your likely working practice correctly: I would probably make a simple re-settable dial for the Myford [there have been several designs published] and engrave it with 127 un-numbered divisions.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Robin teslar on 07/11/2014 08:20:50:

Yes the dial gauge is essential also but doesnt divide by 2 (although I think Ive seen a DRO that does? cant remember where)

.

Robin,

You might consider making a new scale for the DTI

… it could be the simplest solution to the whole problem.

MichaelG.

[Neil WyattModerator @neilwyatt]

Has this thread gone down a blind alley… both 8 tpi and 12 tpi have been mentioned, but the actual pitch of the screw on an ML7 top slide is 10tpi!

So, as the thread is 10 tpi, why not just make a 100 division handwheel, 1 div=1 thou or 2.54mm within 1.6%,, i.e. over 10mm the error will only be 0.016mm.

If you want better accuracy, make a geared arrangement like George Thomas did, only downside is that if you aren't GHT you may loose more accuracy from backlash etc. than you gain.

For a 10 tpi leadscrew this table shows numbers of handwheel divisions and the step down ratio from dial to screw. Note that this does reverse the direction you turn the handle!

	Grads	Ideal ratio	Handwheel	Screw	Ratio	Error
ratio handwheel to screw	40	0.3150	41	130	0.3154	0.1%
2.54:indicated	50	0.3937	41	104	0.3942	0.1%
0.02mm/grad	60	0.4724	42	89	0.4719	-0.1%
	80	0.6299	63	100	0.6300	0.0%
	100	0.7874	63	80	0.7875	0.0%
ratio handwheel to screw	40	0.3937	30	76	0.3947	0.3%
2.54:indicated	50	0.4921	30	61	0.4918	-0.1%
0.025mm/grad	60	0.5906	42	71	0.5915	0.2%
	80	0.7874	39	50	0.7800	-0.9%
	100	0.9843	60	61	0.9836	-0.1%

Construction could follow the design in the Model Engineers' Workshop Manual, P.203.

Neil

(Although for the life of me I don't know why just fitting a 100-division collar isn't the best solution)

[Jon GibbsParticipant @jongibbs59756]

A thought occurs, and I don't know whether it would help, when trying to work metric with imperial dials.

I have just used Harold Halls top-slide method of putting on fine cuts using 6 and 0.6 degrees for 10:1 and 100:1 fine feeds but this could be adapted to do the conversion from imperial to metric over short cuts.

I think if you can accurately set the top-slide at 23.19 degrees to the lathe bed then 10 thou on the top slide would result in an advance the inward feed by 0.1mm.

Sine(23.19) = 0.39378 which is almost exactly 10/25.4.

To set this angle precisely it would be necessary to check for a 0.500" advance for a movement of 1.270" advance of the topslide using this set-up. See the Achieving Precise Diameters Section here… .**LINK**

Hope this helps

Jon

[Author]

Posts