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Martin Cleeve's Rack Tailstock Designs

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Martin Cleeve's Rack Tailstock Designs

Martin Cleeve's Rack Tailstock Designs

In 1956 The Model Engineer published a design for a Myford rack tailstock modification, 'the Rack Tailstock' by Martin Cleeve. In 1960 it published a revised version for the EW lathe.

Neil Wyatt21/08/2014 17:09:44
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I have added a new article linking to pdf versions of two of Martin Cleeve's rack tailstock designs.

It also gives issue numbers for some more recent designs to be found in the online archive.

**LINK**

Neil

ega24/08/2015 11:54:17
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I have been planning a rack feed tailstock along the lines of Anthony Mount's and, like him, wondered what to make the new barrel from (ME 4211 p746). He opted for silver steel thinking that PGMS might bend when the rack was cut. Martin Cleeve also favoured silver steel in his 1956 article although for other reasons. I assume that Anthony Mount's barrel did not distort since his project seems to have been very successful.

Does anyone know why this should be so or have any more general advice to offer, please? It occurs to me that the depth of the rack in proportion to the barrel diameter may come into it. Anthony Mount's was 32mm and mine is 1 1/2". There is also the keyway to consider which in my case would be at 90 degrees to the rack.

Silver steel is relatively expensive and, instinctively, I feel that apart from the danger of distortion a piece of BMS would do the job provided it was dimensionally accurate and of reasonable surface finish.

Roderick Jenkins24/08/2015 12:39:07
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BMS , Bright Mild Steel or BDMS (as it used to be called, the D standing for Drawn) is sized by passing it through a die that induces stress in the outer surface. Machining one side will tend to unbalance the stress forces, resulting in distortion. My assumption is that silver steel is manufactured by annealing ( to make sure it is in the soft state) and then grinding whereas, presumably, PGMS is just ground enough to bring it to size (can anyone confirm?)

If you are prepared to machine the whole surface yourself then black bar should be distortion free.  BMS is usually a thou or two under the nominal size.

HTH

Rod

Edited By Roderick Jenkins on 24/08/2015 12:40:21

Michael Gilligan24/08/2015 14:13:36
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Posted by Roderick Jenkins on 24/08/2015 12:39:07:

My assumption is that silver steel is manufactured by annealing ( to make sure it is in the soft state) and then grinding whereas, presumably, PGMS is just ground enough to bring it to size (can anyone confirm?)

.

I believe that's a valid assumption, Rod

One other point worth mentioning is that Silver Steel is usually centerless ground, and can (occasionally) be slightly lobate [Neil and I have discussed this in the past] ... Whereas the P in PGMS stands for Precision; and it is/was ground between centres. ... I haven't bought any for many years; so perhaps someone else could confirm.

MichaelG.

P.S. ... Good choice of 'reprint', Neil yes

Neil Wyatt24/08/2015 14:53:45
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<checks watch>

Neil

Ajohnw24/08/2015 19:02:49
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The effect the 50p piece has had on centreless grinding never ceases to amaze me.

I'm pretty sure some one has made part of this tailstock capstan head on my boxford.

boxfordcapstantailstock.jpg

There is a bit of a problem with it as it's not hardened. At some point in it's life a slightly inaccurate morse taper has been used in it which has had the effect of expanding the end a little. It's a pretty exact fit so the quill wouldn't go completely back into the body of the tail stock until I lightly sand the very end down.

I can cope with opening out holes with a 1in drill but it does take more effort than the usual screw arrangement would. I would normally do that from 5/8in or 1/2in depending on the material. I don't find it hard to provide the right level of feed or to prevent brass from grabbing using ordinary drills. 1 rev is 3in and it has 1/8in graduations. The arms are about 4in long. The fit is so precise that feeding in very fine drills wont have much feel as it's fairly stiff.

It's not rust - i's black - no idea what caused it.

John

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Edited By John W1 on 24/08/2015 19:03:50

Michael Gilligan24/08/2015 20:09:05
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Posted by John W1 on 24/08/2015 19:02:49:

I'm pretty sure some one has made part of this tailstock capstan head on my boxford.

boxfordcapstantailstock.jpg

There is a bit of a problem with it as it's not hardened.

.

John,

That's an E.W. Cowell [of Watford] tailstock adaptation, and they were supplied soft.

... I bought mine, new, from N. Mole & Co. [a.k.a Amolco]

MichaelG.

Ajohnw24/08/2015 20:38:07
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The only identification on it is what looks like the number 2008 cast into the casting so I assumed at some point some one had done a kit casting for it. I have the original tailstock but for various reason have left this one on.

Just thought people should be aware of possible problems. In practice the morse taper may have enlarged the whole quill a little. There is a lot of mechanical advantage from wedges with such a low angle. Or maybe it just made the fit of the morse taper more precise. I don't get slippage problems.

John

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ega25/08/2015 08:46:46
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Roderick Jenkins and Michael Gilligan:

Thank you both for your helpful comments. I recall the lobate silver steel point from some years ago, the problem being that the out of roundness could not readily be detected by a micrometer; rolling the bar on a flat surface would give an indication, however.

A quick google suggests that some "precision" ground bar is indeed centreless ground and I notice that the manufacturers of silver steel emphasise the precision of their product so I think the point about the grinding method is unresolved. My impression is that industry would want to use the quickest and cheapest method. I did see references to the annealing of silver steel.

I like the black bar suggestion although I think that I would have difficulty in buying a short length and therefore I will probably go for silver steel and try to obtain an assurance about its roundness.

John Stevenson25/08/2015 09:01:17
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I have a combined lever feed, straight lever,not rack, and still kept the screw feed.

The lever feed is fine for drills up to about 1/2" but after that it takes a bit of leaning on the lever. I had a factory Myford lever feed on my ML7 and this worked great but because it was a ML7 it was limited on what it could do so capacity of the lever feed was equal to the machine.

When I did mine I looked a a rack feed but discounted it as it was harder to make and when i have the capstan attachment fitted the spoked handle always seems to get in the way and I didn't think the tailstock would be any different.

If you want something fancy then you could always replicate the tailstock feed on the Cazeneuve lathe.

The capstan on this has three positions by lifting the spokes up / down.

One is lever feed, one is handwheel feed from the handle at the front and one is power feed from a central shaft not in the picture.

Ajohnw25/08/2015 09:09:07
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I feel I have to point something out. Centreless grinding is used rather a lot for 2 reasons. It's convenient and in terms of roundness tolerance and repeatability more precise than between centre work. It can also be arranged to work up to shoulders and to produce tapers. Convenient largely relates to the ability to easily hand long lengths.

On the other hand if people want to believe otherwise that's fine by me. I just happen to know why it is sometimes favoured for mass production work. A similar idea is used in other areas as well.

John

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John Stevenson25/08/2015 09:26:14
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Posted by John W1 on 25/08/2015 09:09:07:

I feel I have to point something out. Centreless grinding is used rather a lot for 2 reasons. It's convenient and in terms of roundness tolerance and repeatability more precise than between centre work. It can also be arranged to work up to shoulders and to produce tapers. Convenient largely relates to the ability to easily hand long lengths.

John

.

It's main claim to fame is speed, pure and simple and the ability to do long lengths.

Between centre work can also work to shoulders and do tapers. One of the most precise jobs done today in mass production are parts for diesel injection pumps. These are all done on conventional grinders, well special grinders but working on conventional methods. Centreless grinding is not used for these parts.

Michael Gilligan25/08/2015 09:28:59
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Posted by John Stevenson on 25/08/2015 09:01:17:

If you want something fancy then you could always replicate the tailstock feed on the Cazeneuve lathe

.

That's very classy, John

MichaelG.

Ajohnw25/08/2015 11:28:05
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Posted by John Stevenson on 25/08/2015 09:26:14:
Posted by John W1 on 25/08/2015 09:09:07:

I feel I have to point something out. Centreless grinding is used rather a lot for 2 reasons. It's convenient and in terms of roundness tolerance and repeatability more precise than between centre work. It can also be arranged to work up to shoulders and to produce tapers. Convenient largely relates to the ability to easily hand long lengths.

John

.

It's main claim to fame is speed, pure and simple and the ability to do long lengths.

Between centre work can also work to shoulders and do tapers. One of the most precise jobs done today in mass production are parts for diesel injection pumps. These are all done on conventional grinders, well special grinders but working on conventional methods. Centreless grinding is not used for these parts.

I wouldn't disagree that cylindrical grinding can better centreless especially of late given vast amounts of attention to a number of things but the centreless machines are basically a lot simpler and can hold very precise tolerances. The roundness aspect is pretty trivial to achieve and way better than the the typical +/-0.0005in for normal precision cylindrical grinding between centres. Here is what one company offers for instance

**LINK**

I did see a special purpose machine tool in the mid 60;s diamond turning parts to a total tolerance of 0.0002in that had to use a centre but it also used an air bearing to achieve that. I'd guess a part came off it every 20 sec or so all day long.

John

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John

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John Stevenson25/08/2015 12:48:33
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Posted by John W1 on 25/08/2015 11:28:05:

I wouldn't disagree that cylindrical grinding can better centreless especially of late given vast amounts of attention to a number of things but the centreless machines are basically a lot simpler and can hold very precise tolerances. The roundness aspect is pretty trivial to achieve and way better than the the typical +/-0.0005in for normal precision cylindrical grinding between centres. Here is what one company offers for instance

**LINK**

John

-

.

That link supports what i say, they can achieve better tolerances on cylindrical grinding than on centreless and remember that these are best tolerances and you will pay dear for them.

However this thread is degenerating, as usual, into the realms of theory.

As regards the OP then a length of silver steel will be more than good enough for the project IF it is available in the size required. One example is the Super 7 which has a barrel size all of it's own.

I did go back and read the original article and saw no note about lobed material, material moving under stress and I dare say that if you peruse the post bag press of the day, none of these items would have been mentioned.

I wonder why that was ? Was it because people just got on with things [ probably judging by the articles of the day ] or writing a letter was too much trouble whereas penning a reply via the t'internet is far easier.

Ajohnw25/08/2015 14:29:24
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160 photos

I did go back and read the original article and saw no note about lobed material, material moving under stress and I dare say that if you peruse the post bag press of the day, none of these items would have been mentioned.

I wonder why that was ? Was it because people just got on with things [ probably judging by the articles of the day ] or writing a letter was too much trouble whereas penning a reply via the t'internet is far easier.

I agree with that especially get on with it. And would wonder if the 50p piece was around then. It wont rotate between 3 points. The internet is a wonderful place but can give people far too many things to worry about even distortion due to machining one side - why not do it and see what happens even if just a trial part.

On my Boxford the expansion effects are real but haven't really caused any problems other than the one I mentioned. Like many smaller lathes the quill diameter is on the low side to what might be called industrial stuff.

The quill diameter is just a couple of 1/10 thou under size. If some one is hoping to use silver steel to avoid machining that aspect I suspect they may find it difficult to get some that close to the correct size.

John

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ega25/08/2015 14:48:03
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John Stevenson:

I have had a Myford lever feed in amateur use for several years and much prefer it to the standard screw feed. My lever needed overhauling to remove play in the bearings and I have also fitted it with an improved, longer handle with more comfortable grip. The positive experience with the Myford was one reason for wanting to modfiy my larger lathe and I did think about a scaled up lever feed but felt it would be unsatisfactory partly because I couldn't see how to design a linkage that would give me the length of barrel movement that I want. I shall not be emulating the superb Cazeneuve although I do plan to incorporate the capstan within the body of the tailstock rather than hang it off the end.

Good point about the Super Seven barrel: mine is 1.115" diameter which is certainly not a standard size for silver steel. I have ordered a length of 1.5" material for my project and the supplier assures me it will be round and that I may return it if proves otherwise.

Can you tell us how your combined screw and lever feeds contrive to co-exist?

John Stevenson25/08/2015 15:10:29
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EGA.

On site at moment but I'll be in touch via PM.

 

Cancel the silver steel you don't need it, my mod uses all the existing parts and all that is needed extra is just BDMS and don't matter if its lob sided, in fact you could do it out of a bit of square, triangular or hex if you could make a hole to fit.

 

No microns will be harmed doing it but the odd post code could come under fire. wink

 

[Edit]  reread the post and you want to use a capstan built into the tailstock. Need to think about this as may not work as is.

Will still be in touch.

Edited By John Stevenson on 25/08/2015 15:12:22

Michael Gilligan25/08/2015 16:54:24
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Posted by Michael Gilligan on 24/08/2015 14:13:36:

One other point worth mentioning is that Silver Steel is usually centerless ground, and can (occasionally) be slightly lobate [Neil and I have discussed this in the past] ... Whereas the P in PGMS stands for Precision; and it is/was ground between centres. ... I haven't bought any for many years; so perhaps someone else could confirm.

.

If I need to apologise for mentioning that Silver Steel can (occasionally) be slightly lobate, then here goes:

... SORRY ...

It was just a passing comment; I wasn't trying to start WWIII.

MichaelG.

ega25/08/2015 17:20:43
1116 forum posts
92 photos

John Stevenson:

Many thanks. I have sent you a PM.

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