Author Topic: Tailstock rack handle position?  (Read 9202 times)

Offline PeterE

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Tailstock rack handle position?
« on: July 31, 2012, 05:39:47 PM »
I have been thinking of a way to be able to switch between the ordinary tailstock screw feed and a new tailstock rack feed. I also think I have found a suitable solution. After further searching I have also found that there seems to be three main positions used for the "star wheel":

   1 - Vertical, in front of the user (Schaublin f ex) (counter-clockwise rotation)
   2 - 45 degrees up, (Radford, Stepperhead f ex) (counter-clockwise rotation)
   3 - horizontal, on top of the tailstock (Myford and Michael Rhodes for the Unimat)
        (clockwise rotation)

All three are most probably equally good so my question would be: Is any of the three to prefer before the others ????????????

BR

/Peter
Always at the edge of my abilities, too often beyond ;-)

Offline PekkaNF

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Re: Tailstock rack handle position?
« Reply #1 on: August 01, 2012, 05:45:17 AM »
......I also think I have found a suitable solution..../Peter

What do you have?

I saved a Citroën Xantia steering unit, It has an steering axle (pinion) at an angle and I tought that after I have cleared some of the crap (trasures) of my garage I'll see if it could make tailstock capstan.
1) I just was thinking that it would be nice if the capstan wheel (or arms) would not interfere with cross slide wheels and lathe parts when in use. I would imagine that pretty big capstan wheel is needed for big drills or shaping (i.e internal groves or such). Then again if you are using small drills, your consideration might be different. There fore I was thinkking that pinion axle aimed outwards and back (i.e. capstan wheel vertical, but axle direction outwards at an angle) would give max power to turn and still clear much of the cross slide controls. Small wheel might be best when at right angle to rack.
2) I have no idea what would be "natural" direction, but I would use same logic than on the cross slide wheel. Mine is that when turned at the top of the wheel, thingies moves towards the chuck, ie. with the hand.

Pekka

Offline PeterE

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Re: Tailstock rack handle position?
« Reply #2 on: August 01, 2012, 03:25:23 PM »
OK, I guess I have to give a little more info.

I started out with making a requirement list as follows:

   1 - The new item shall be exchangeable with the "old" one.
   2 - Both items shall be possible to use.
   3 - Minimal alteration to the existing tailstock is preferable.
   4 - It must be possible to make the new item using a mini lathe and a mini mill.
   5 - No exclusive materials shall be used
   6 - The new item shall be designed as simply as possible.
   7 - It must be easy to change between the two items.

This means that I donīt want to discard the original screw-feed attachment, but rather get more possibilities by adding the new one. I started out by thinking of how I could get access to the existing quill from behind with something else than the hand-wheel and the screw. Then if it was possible to replace what was removed to make the "old" item a complete exchangeable unit easily removed or secured.

What came up was as follows:

The first problem is to solve how to create the access to the quill and still not ruin the whole thing. It turned out that the end of the tailstock at (A) have a thicker end wall - a little less than 12 mm (1/2") - there are three holes, two for securing the visible thick washer locking the feed screw in place and one for the feed screw itself.

Now, if I drilled/bored out the wall and replaced it with a suitable thick "washer" or end replacement block (B) then I could re-use all the items as today at (C). Using two screws from either top/bottom or from the sides it should be possible to lock the whole thing securely in place. It could actually work.

But how does it look for a rack feed then? I re-drew the stuff to get an idea of how the rack feed housing could be fitted using the same manner of fitting.

Provided that the rack is not larger in diameter than 20 mm and uses a suitable DP or Module it should actually be feasible. The star-wheel block is just a sketch so far.
How large is the car steering rack from the Citroen? I have a scrap merchant fairly close and if I could get a used steering rack that would solve some machining I am not confident with.

Well, then came the question about the position of the star-wheel housing and which way the wheel should be rotated to feed the rack to the left (seen from the user perspective).

The difference in position can gain around 50 mm (2") back to front depending och choice. Then came the question at what angle to place the rotational axle of the star-wheel, vertical, horizontal, or in between? With the right choice the new rather larger "handle" will still not be in the way when manoevering other controls on the machine.

If we look at the different positions from the tailstock towards the headstock it looks as follows:

I would say that it is possible to put on the same amount of force regardless of position, it is more important that the handles does not foul (not faul as I have written in the picture ) any other control or get in the way of work or man.

I think I have to make some assumptions and a mock-up to get another step forward, meanwhile any comments are very valuable as I am not a machinist by trade and hence donīt have that hands-on experience. (My "trade is software, information and information systems.)

I hope that I didnīt scare you off

BR

/Peter
Always at the edge of my abilities, too often beyond ;-)

Offline Fergus OMore

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Re: Tailstock rack handle position?
« Reply #3 on: August 01, 2012, 04:09:19 PM »
On the 12th July 1956, the late Martin Cleeve( K.C Hart) published the first of two articles in Model Engineer of what he called a 'Skew Rack tailstock mechanism' as part of the numerous modifications to his Myford ML7. I recall that he embodied the design in a homemade miniature lathe which he fabricated and also fitted it into a friends's Super Exe lathe.

In his article he mentioned that the proving of the design had already been carried out on his earlier wartime ML4.

As far as I am aware the mention of 'Radford' or J.A.Radford constructed a much more complicated mechanism, similar to Murad Bormilathe 'Elevating Heads'.
The 'Radford' suggests completely replacing his Myford Super7 tailstock in an effort to make a lathe which will did fairly complicated milling as well. His Super7 also was a substitute to a conventional tool and cutter grinder.

I hope that I have gone someway to clear up possible confusion and to provide a series of references to 'other lathes'

Offline PeterE

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Re: Tailstock rack handle position?
« Reply #4 on: August 01, 2012, 04:18:39 PM »
Hi Fergus,

Thanks for the info about Martin Cleeve and his design, I did not know about that one before. It would be interesting to see how he did it as I know he was a clever designer.

Please note that I do not even for a blink think that I am putting something unique together, but rather an adaptation of a well known item to suit a particular machine.

I do have J A Radfords book "Improvements and Accessories for your lathe" in my collection as a reference. It is true that he made a Murad Bormilathe type setup with elevating heads for his Myford. It is from the elevating heads tailstock I have seen his ideas and they are in that case not very complicated (compared with some other stuff he made).

Thanks again for the references.

BR

/Peter
Always at the edge of my abilities, too often beyond ;-)

Offline Fergus OMore

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Re: Tailstock rack handle position?
« Reply #5 on: August 01, 2012, 04:44:48 PM »
Hi Peter,
             I suspect that I still have all the Cleeve article as a photocopy.
It is tucked in behind Chaddock's original Quorn articles. What seems important is that Cleeve's stuff was extremely simple and cutting the rack on his lathe was fully explained.
I'm still not very well after a month of pneumonia but could try to copy the copies which were somewhat ancient and prior decent home photocopying.

Perhaps a PM with a proper e-mail add will get you  the information

Offline PeterE

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Re: Tailstock rack handle position?
« Reply #6 on: August 02, 2012, 04:48:31 PM »
After some e-mail conversation I have got some new info to add to my thinking, will be back when done.

Another question on the fly; In most cases the rams are made from  ordinary bar stock of suitable diameter, but would it work equally well with a threaded rod? I am thinking of a stainless threaded rodding which I think keeps to sizes better than ordinary galvanized ones, and the A2 quality should still be OK to machine.

Using a threaded rod of 20 mm dia x2.5 mm pitch would make for quite a rack, and to make a "nut" to drive it should be possible using a tap of the same size.

Just an idea to easily find material...

BR

/Peter
Always at the edge of my abilities, too often beyond ;-)

Offline andyf

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Re: Tailstock rack handle position?
« Reply #7 on: August 02, 2012, 07:05:03 PM »
Getting back to the ergonomics, Peter, I think that the three diagrams you showed point the way. Taking drilling a hole as an example, in A it would be natural to grasp the handle which is nearest to you and move it CW it towards the headstock to apply pressure on the drill bit.

In C, it would be equally natural to grab the topmost handle and move it CCW.

B is the problem situation, where you might need to think things out.

Personally, I would go for A, because there is very little chance of the arms fouling anything as you turn them. Even better would be half-way between A and B, so that the arm nearest to you was more or less horizontal.

Andy
Sale, Cheshire
I've cut the end off it twice, but it's still too short

Offline PeterE

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Re: Tailstock rack handle position?
« Reply #8 on: August 03, 2012, 12:29:37 PM »
Hi Andy,,

I can only agree with you here. I have come to the same conclusion myself, and I think I want to make a mock-up out of odds and ends just to find the right angle och the gear housing and the angle on the star wheel arms vs the gear housing.

As you say the housing should probably be nearer the A position than half way between A and C, but how much will be decided by the angle of the arms, and with the right combination the star wheel will not foul any other handle either.

I did get some more info = the old Martin Cleeve descriptions and found some useful info there as well. He had decided to skew the star wheel axle to be in a horizontal position but turned about 20 degrees outwards to the right thus turning it away from the bed handle and such.

Still working out the boundaries and types of items, and then I willb e back with more.

Thanks for comments they really help much in differnt ways.

BR

/Peter
Always at the edge of my abilities, too often beyond ;-)

Offline PekkaNF

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Re: Tailstock rack handle position?
« Reply #9 on: November 15, 2012, 04:46:52 AM »
How is this  :proj: coming up together?

Saw this;
http://www.lathes.co.uk/elffers/img16.jpg

And remembered this thread,
Pekka

Offline PeterE

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Re: Tailstock rack handle position?
« Reply #10 on: November 15, 2012, 11:47:52 AM »
Hi Pekka,

Well, the project is still in design stage (meaning that I have too many projects going at the same time so it has to wait for a bit more  :palm: ), but is on the ToDo-list.

Nice picture, I haven't seen that one before on that size of tailstock. I believe that an Australian machinist presented a solution like that in MEW but for a Unimat size machine. (Thatīs where I got the idea about using a threaded rod instead of a rack).

BR

/Peter
Always at the edge of my abilities, too often beyond ;-)

Offline evildrome

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Re: Tailstock rack handle position?
« Reply #11 on: September 09, 2013, 10:08:56 AM »
Hi Peter,

 Did you ever finish this? I ask because I am considering something similar for my Colchester Bantam.

 Probably sized similar to the Shaublin 125 tailstock capstan.

Cheers,

 Wilson.

Offline PeterE

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Re: Tailstock rack handle position?
« Reply #12 on: September 09, 2013, 03:24:25 PM »
Hi Wilson,

Its kind of embarrassing to admit that I haven't advanced anything with this so far.

Unfortunately my hobby life meanders quite a lot between model railroading, model engineering, gardening and that what takes most of my time and pays my bills - daily work. Even though my work is interesting I wouldn't call it a hobby though ....

Anyway, the idea is not forgotten and I think I have a couple of solutions slowly maturing in my head so one day I will make it, and then I will make it so that I can use both the ordinary standard hand wheel and the rack as exchangeable features.

So please do not wait for me, have a go at it yourself. It is always very interesting and educational to see others solutions.

BR

/Peter
Always at the edge of my abilities, too often beyond ;-)

Offline evildrome

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Re: Tailstock rack handle position?
« Reply #13 on: October 16, 2013, 08:18:51 AM »
Yes, my work interferes with my hobbies as well...

Ce la Vie.

If I ever get round to this I will post my solution.

These Shaublin guys are nothing if not inventive...

http://www.lathes.co.uk/schaublin/page23.html

Cheers,

 Wilson.
« Last Edit: October 16, 2013, 08:58:06 AM by evildrome »

Offline Meldonmech

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Re: Tailstock rack handle position?
« Reply #14 on: November 25, 2013, 02:53:38 PM »
Hi Wilson

                   Just came across your Schaubalin Tailstock references from Lathes.com, very interesting, thanks for posting.

                                                          Cheers David

Offline evildrome

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Re: Tailstock rack handle position?
« Reply #15 on: January 08, 2014, 09:59:47 AM »
Yes, its extremely funky. Seems to incorporate depth stops and the option for lever arm / sensitive drilling attachment.

In fact its so funky I find the idea of making one quite daunting...