Latest Project - Adjustable Tailstock for Dividing Head

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awake

Latest Project - Adjustable Tailstock for Dividing Head

Post by awake » Wed May 20, 2009 8:47 pm

A few years ago, shortly after I started learning machining, I acquired a second hand spin-indexer -- just the indexer, no tailstock. A year or so later I acquired a second hand dividing head. Again, you guessed it -- no tailstock. I've used both without a tailstock ever since, but more than once I've been pushing the envelope without a tailstock to stabilize the free end.

I finally got around to finishing a tailstock that can be used with either the indexer of the DH. I started this project back about the time I got the indexer, when I was still very new to machining; at that time I machined the two blocks so that they would slide on a "square way" of sorts. I might do this differently if I designed it today, but ... no reason to start over. However, the project languished for a few years, waiting until I really, really, really needed a tailstock.

Well, now I really, really, really need a tailstock! So I finally finished the project. I'm pleased with the results.

Here are some pictures -- first the assembled tailstock, from several angles, and then a shot of the disassembled parts. The rod with the 60-degree center point on one end is made from 5/8" W1, which I hardened and tempered. It will adjust horizontally around 1" by way of a brass adjusting nut at the rear; it can be locked into place with a split "pinch" sleeve actuated by a 1/4"-20 SHCS on the side of the block that carries the center. The block that carries the center has a .520" pin pressed into it that projects into a slot in the main upright. A 1/4"-20 SHCS threads through this pin to allow the block to be raised or lowered as needed; it has a range of around 2" of travel. Two 1/4"-20 SHCS slide in slots and lock the block into the desired position.

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mike71

Post by mike71 » Wed May 20, 2009 8:52 pm

THATS COOL ! Great job.............

websterz
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Post by websterz » Wed May 20, 2009 9:02 pm

Great design!! I have been looking to build a tailstock for my own rotab, mind if I copy yours? :D

awake

Post by awake » Wed May 20, 2009 9:33 pm

websterz wrote:Great design!! I have been looking to build a tailstock for my own rotab, mind if I copy yours? :D
Feel free . . . especially as I can't really claim that there is a design, as such. Usually when I machine something I draw it up on a CAD program, but this one I mostly just did by the TLAR method (that looks about right). :)

A large part of the "design" was dictated by the fact that I acquired a stock of 1" x 3" x 12" steel blocks for free -- they came out of a discarded weight machine. I don't know the exact composition of the steel, but I strongly suspect that it was leaded steel, because it machines very, very nicely. So the tailstock is 3" wide, and each of the blocks started out 1" thick before machining the "square ways." The main upright is a little under 4" tall; the movable block is around 2.5". The base on which it all sits, and which will be used to clamp to the table, is 3" x 3" x 1/2" thick. Had I not already cut this (several years ago when I first started the proejct), I would have made it a little larger.

One bit of advice that may not be obvious -- the split sleeve that pinches the center to lock it in place is 1/2" diameter. This hole is set so that it overlaps or protrudes slightly into the .625" bore that the center slides in. I meant to have it protrude about .050" into the bore, but due to a brain malfunction when I was laying out, it only protrudes about .012". I was concerned that it would either not provide adequate clamping power, or that it would be hard to unclamp because of wedging itself into place. As it turns out, it does work okay ... but I'd still advise going with .050" or even more.

Here's the machining trick for this split sleeve. First drill the hole for the split sleeve. Machine the sleeve as a single piece, about .020" shorter than the width of the block. Drill and tap all the way through, 1/4-20. Use a short 1/4" SHCS or bolt with a washer and tighten it all the way up on one side. Slide the sleeve into the hole with the bolt & washer on the outside face. Use another short SHCS or bolt and washer on the other side; tighten very securely so that the sleeve is held immobile in its hole. Then drill the .625" hole -- which will simultaneously machine the concave in the sleeve. Finally, remove the bolts and the sleeve, and cut it in half on the band saw, right in the middle of the concave. File off any burrs. Drill out the outside half of the sleeve to 1/4".

When you assemble everything, use a 1/4" SHCS just a bit shorter than the total sleeve length; slide on the outside half and thread on the other half; make sure the concave parts are in the middle! Slide the sleeve into its hole, and adjust so that the concaves situated to fit the .625" bore. Slide in the hardened center rod; you may have to wiggle a bit to get the sleeve pieces just right. Once the center rod is in place, the sleeve can't fall out. When you tighten the SHCS, it pinches the two halves the sleeve together on the center rod, and does an incredible job of clamping it in place.

websterz
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Post by websterz » Thu May 21, 2009 10:45 am

I live by the TLAR method. If I am building something I don't have pre-drawn plans for I just draw it up in my head and go from there. I make less scrap doing it freestyle than I do following a print anyway...more freedom to nudge and tweak. :D

Thanks for the tips on the pinch clamp. I would have cheated and gone with a slotted center and a brass tipped setscrew. I like your idea better.

Black_Moons
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Post by Black_Moons » Thu May 21, 2009 11:27 am

Very nice design. from your discription the split bushing is actualy threaded and holds your thumbscrew adjustment solid? not the actual tailstock ram? intresting design choice. in the middle of the ways beween the two blocks theres a recess in one, and sorta a OO lump in the other that seems to mate into it.. any reason for all that?
[url]www.Cyberlazy.com[/url]

awake

Post by awake » Thu May 21, 2009 12:45 pm

Black_Moons wrote:Very nice design. from your discription the split bushing is actualy threaded and holds your thumbscrew adjustment solid? not the actual tailstock ram? intresting design choice. in the middle of the ways beween the two blocks theres a recess in one, and sorta a OO lump in the other that seems to mate into it.. any reason for all that?
There isn't what I would call a split bushing; there is instead a "pinch sleeve" -- but maybe we're talking about the same thing. This pinch sleeve clamps the tailstock ram directly. The brass thumbscrew at the back end is only used to adjust, not to hold.

There is a 1/2" diameter pin sticking out of the movable block with a 1/4-20 threaded hole through the diameter -- it doesn't show up very well in the last picture. This pin slides in the recess/slot in the fixed block. A SHCS runs down the middle of that slot and threads into it. This allows for fine adjustment of the height.

Maybe I should go ahead and draw up the CAD drawing -- it is hard to explain this with words!

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JimGlass
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Post by JimGlass » Fri May 22, 2009 8:55 am

That is real nice :D

The SHCS with washer on the top, is that some kind of jack screw to adjust height?

It would be nice if you could have the tailstock plated with black oxide or something.

Nice work.
Jim
Tool & Die Maker/Electrician, Retired 2007

So much to learn and so little time.

www.outbackmachineshop.com

awake

Post by awake » Fri May 22, 2009 9:38 am

JimGlass wrote:That is real nice :D

The SHCS with washer on the top, is that some kind of jack screw to adjust height?

It would be nice if you could have the tailstock plated with black oxide or something.

Nice work.
Jim
Thanks! Yes, the SHCS on top is a screw adjustment for the height. I tried to describe it in my previous post replying to a question from Black_Moons. The picture of the parts just doesn't show clearly enough what is going on ... I've started drawing up a CAD drawing to show what is happening, so maybe that will make it clearer. :)

Yes, a black oxide finish would be nice. It may not be clear from the pictures that I left the black powdercoat finish on the steel blocks anywhere that I could -- that dresses it up and protects it some, but there are some exposed surfaces that I can already see are going to need something to keep the rust at bay ... especially now that it is humid and I tend to have drops of sweat fall on the most vulnerable parts!

Black_Moons
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Post by Black_Moons » Fri May 22, 2009 12:13 pm

ah I get how the height adjustment works now.. very nice design, looks more sturdy then the ones enco sells :)
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Michael Edwards
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Post by Michael Edwards » Sat May 23, 2009 9:51 am

Very nice work. The design is perfect IMO for the home shop machinist. You have some elegant solutions to eliminate complexity and yet function properly. In particular, your split/pinch sleeve. I’m sure if you made the drawings, more than just myself would be grateful. Very nice indeed, thanks for sharing.

ME

awake

Post by awake » Sat May 23, 2009 2:55 pm

Michael Edwards wrote:Very nice work. The design is perfect IMO for the home shop machinist. You have some elegant solutions to eliminate complexity and yet function properly. In particular, your split/pinch sleeve. I’m sure if you made the drawings, more than just myself would be grateful. Very nice indeed, thanks for sharing.

ME
Thanks. As I have time, I will keep working on the drawing; when I get it done, I'll post it here.

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