PDA

View Full Version : Need a suggestion for consistant depth stop for material into lathe chuck...



cuemaker
11-18-2014, 12:28 PM
I am sure somebody has built/designed something already.... Just need a picture/idea..

I will soon have work that will require individual pieces that will need to go into a chuck at a specific distance...Is there a basic tool/rig/jig that will accomplish this?.

Maybe just a piece of rod with collets that fit the bore of my lathe and then position it correctly? I have to figure out how to keep it from moving/flopping around..

All ideas welcomed

EddyCurr
11-18-2014, 12:34 PM
How deep into the chuck: above the face or below?

Royal has overpriced-for-what-they-are spacers. There
are others that as you mention insert through the spindle.

.

Toolguy
11-18-2014, 12:37 PM
Most 5C collets have an internal thread that is made for a collet stop. The outer threads are for the draw tube. If you are using a chuck you can make a stop that goes through the spindle up to the chuck. All thread rod works fine, no need for something exotic or expensive. You can also mill out a spider to go around the chuck jaws of whatever thickness is needed or put a bolt with nut in the middle for an adjustable length.

Cuttings
11-18-2014, 12:38 PM
I built two of them. One comes through the spindle and can be adjusted from the other end.
The second one is used on the outside of the chuck to repeat the amount your work sticks out from the chuck.
I got the design for these from one of the workshop practice series books called Useful Workshop Tools by Stan Bray.

cuemaker
11-18-2014, 12:51 PM
I see I need to be more specific.. I will have a 7"oal x 3/4dia rod that will need to go into a 3 jaw chuck about 4"

I see a collet system would help..I have one, Pratt Burnerd multisize collets..but I have run into issue with the collect holding the work tigh enough, then releasing enough to move the work in and out when it does hold it tighly enough.

I will have to play with it some..

Paul Alciatore
11-18-2014, 02:22 PM
I would definitely go with the collet approach.

But I do not like the idea of adding a stop using the collet's own threads. Think about it. The collet is tightened by drawing it back into the holder. Horizontal motion. That motion stops when it is tight on the part being gripped. But the parts can vary in diameter. So, the inward motion stops at a different place on parts with different diameters. And, due to the taper of the collet, there is a magnification factor at work. A one or two thousandth difference in the part's diameter will be magnified to five or ten or more thousandths in the location of the collet AND the part in it if it is located by a stop affixed to that collet.

I prefer a stop that remains still. Here is my solution, a long, threaded rod with a nut on the outboard end of the collet closer tube. That tube is fixed in position by the end of the spindle and the stop rod stays fixed with it.

http://img.photobucket.com/albums/v55/EPAIII/P1010002-1.jpg (http://smg.photobucket.com/user/EPAIII/media/P1010002-1.jpg.html)

The parts:

http://img.photobucket.com/albums/v55/EPAIII/P1010004-2.jpg (http://smg.photobucket.com/user/EPAIII/media/P1010004-2.jpg.html)

And assembled with a collet:

http://img.photobucket.com/albums/v55/EPAIII/P1010008-2.jpg (http://smg.photobucket.com/user/EPAIII/media/P1010008-2.jpg.html)

The outer end of the threaded rod is knurled for easy adjustment. The tip was turned down to fit in small collets. But it can be cranked out as far as needed so several inches are easily possible. A shorter rod may be desirable for longer parts. The brass nut was made from a brass pipe compression nut and has the original, plain hole. The small brass part is the actual nut for the shaft which is held against the end of the collet closing tube by the larger nut. And the steel knob/nut is for locking it down.

With this stop and a dial indicator on the lathe carriage, it is easy to hold a +/- 0.001" tolerance from part to part.

Yondering
11-18-2014, 04:18 PM
I'm interested in this as well, for my South Bend 9" lathe. Being that it's an MT3 spindle, I don't use collets, just 3 and 4 jaw chucks. Most of the time I'd want a stop would be to repeat the distance the part sticks out of the chuck; for example when turning a long piece of rod into several identical parts.

Suggestions appreciated, pictures would be especially helpful.

Ridgerunner
11-18-2014, 04:30 PM
It depends on how deep and if your chuck allows it; but they make soft jaws in different sizes.

http://i1122.photobucket.com/albums/l539/ridgerunner1212/Softjawsbox-Copy.jpg (http://s1122.photobucket.com/user/ridgerunner1212/media/Softjawsbox-Copy.jpg.html)

http://i1122.photobucket.com/albums/l539/ridgerunner1212/Softjawsonchuck-Copy.jpg (http://s1122.photobucket.com/user/ridgerunner1212/media/Softjawsonchuck-Copy.jpg.html)

JCHannum
11-18-2014, 06:27 PM
There are commercially manufactured units available, but one is easily shop fabricated. It is basically similar to an expanding mandrel that is inserted into the spindle and tightened with a long wrench once in position.

http://www.yuasa-intl.com/images/products/pdfs/swt.pdf

JRouche
11-18-2014, 07:04 PM
The yuasa tool is nice, a bit expensive. This expander from harbor freight could be modified to do the same thing. Ten bucks. It does come in other sizes. JR

http://i1183.photobucket.com/albums/x461/_GLE_/HSM/expander_zps04e5a0fb.jpg (http://s1183.photobucket.com/user/_GLE_/media/HSM/expander_zps04e5a0fb.jpg.html)



http://www.harborfreight.com/small-tail-pipe-expander-69550-9156.html

Tinkerer
11-18-2014, 07:11 PM
I see I need to be more specific.. I will have a 7"oal x 3/4dia rod that will need to go into a 3 jaw chuck about 4"

I see a collet system would help..I have one, Pratt Burnerd multisize collets..but I have run into issue with the collect holding the work tigh enough, then releasing enough to move the work in and out when it does hold it tighly enough.

I will have to play with it some..

Why not just use a... adjustable square set your part in the chuck to depth. Adjust square from face of chuck or jaw. Place next bar proud in chuck light pressure... place square on end and push in snug up jaws and go.

Quick and simple... :)

KiddZimaHater
11-18-2014, 07:29 PM
Why not just use a... adjustable square set your part in the chuck to depth
Agreed. Or get yourself a Stop-Loc gadget like this:
.
http://www.penntoolco.com/images/catalog/11207.gif

lakeside53
11-18-2014, 07:55 PM
Mine has two Aluminum bushings and a rod. Took me less the 10 minutes to make. The rear-most is flanged and locks onto the spindle exit, the other slides in as far as required and can reach to the chuck. Rod is locked to both bushings with set screw. The rear set screw is used for moving/locking the rod. Dead easy, repeats to a thou or better. I can part off 0-24 inch rods just with the internal length of the spindle and chuck ; more if I cut away from the chuck.

A threaded adjuster would make it easier for tiny adjustments, but I seem to stumble through by simply moving the carriage and locking it.

boslab
11-18-2014, 08:09 PM
How about a stationary brass tipped rod up the bore, fixed to the lathe, suppose you could stick a depth gauge on it too
Mark

TOOLZNTHINGS
11-18-2014, 08:35 PM
Aloris makes expanding spindle stops. I bought one and made one. Very easy to use and you can make different stop rods to go in the body to match your needs.

Oldguy
11-18-2014, 09:01 PM
Here's a link to a thread on PM showing what some people built for spindle stops:

http://www.practicalmachinist.com/vb/general/making-spindle-work-stop-lathe-294042/

Glenn

CalM
11-18-2014, 09:51 PM
I've got a simple rig for the 16 inch Mazak

A "cat's head" sleeve that clamps to the far left spindle tube. (vis. a sleeve with three set screws)

The sleeve has a simple piece of flat stock welded across the diameter with a hole drilled through the center, and a 1/2-16 nut welded on.

A two foot length of all thread is run into the nut, with a second jamb nut to secure position. The all thread sticks down into the spindle bore, and can stop any work from moving towards the left end (into the chuck)

Anything can be added to the all thread to fill the spindle bore, or suit the work.

Adjustment is done at the left end.

A couple of bucks worth of scrap, and 1/2 hours work.

t'werks a treat!

Paul Alciatore
11-18-2014, 09:55 PM
My collet stop, pictured above in post number 6, is exactly for a SB 9. Yes, it does have an MT3 spindle, but it came with a collet adapter for the 3C size collets. You can use MT3 collets if you can find them, but the adaptor and 3Cs are a lot easier to find. 1Cs also fit the adaptor.

The collet adapter is a simple part and you could make one yourself. MT3 on the outside and 3C on the inside. Just one hunk of steel. Do the OD first and slip it in to do the inside with a 3C taper. That's all there is to it.



I'm interested in this as well, for my South Bend 9" lathe. Being that it's an MT3 spindle, I don't use collets, just 3 and 4 jaw chucks. Most of the time I'd want a stop would be to repeat the distance the part sticks out of the chuck; for example when turning a long piece of rod into several identical parts.

Suggestions appreciated, pictures would be especially helpful.

lakeside53
11-18-2014, 09:58 PM
I find it's not just "what sticks out of the chuck", but the total length control - i.e. also "what sticks back into the spindle". OK, I have 1.5 inches of pass though, but even a sb9 can use the spindle bore to great effect now and then ;)

Paul Alciatore
11-19-2014, 01:44 AM
Lakeside said it. If you set the part's position from the front of the chuck, then you have no idea about how much is inside the chuck or spindle. So you can not finish it to a specific length or machine features at a fixed point relative to the hidden end. So a square or the Stop-Loc gadget are of no help here.

The idea is you finish one end of a part and then reverse it in the chuck or collet and finish the other end. It is when you are doing the "other" or second end that the need for precise positioning comes up. And that positioning must be done relative to the already finished end, which is now inside the spindle.

The square or Stop-Loc device would be helpful when setting the first end out of the chuck to place it in a known starting position. This would allow using the same settings/readings for finishing that first end.