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View Full Version : Repeating the same lenght sticking out of lathe chuck?



Black Forest
11-07-2012, 01:31 PM
I need to make 100 shoulder bolts. I have the hex stock. After I part off the finished bolt I loosen the chuck and slide the hex stock out for the next bolt. I have a DRO on my lathe and it would be good if I had some sort of stop to use for the proper stickout. Now I just zero the DRO at the end of the stock. I was wondering if there is a better way?

The hex stock is 22mm. I turn down to 16mm for 21mm and then down to 10mm for 14mm. I have my 10mm die mounted on the tailstock in my releasing die holder that is set to trip at 14mm. It is quite quick to make the bolts. Two passes with the lathe, run the die and then part off. Next.

Suggestions?

Jaakko Fagerlund
11-07-2012, 02:06 PM
Make a small jig that is like an L-shaped, so that the long leg is the emount sticking out of the chuck. In use, loosen your stock, put the L against a chuck jaw and pull the stock up to the L's end and tighten.

Can be made as one-off or with a longer threaded rod with nuts so that the length is adjustable :)

JCHannum
11-07-2012, 02:13 PM
Or, use an adjustable machinist's square.

krutch
11-07-2012, 03:49 PM
Why don't you use the tool tip or tool holder as a stop? I will move the tool post to a designated dro reading and use it as a stock stop. I usually give a little extra for clean-up stock when I do this. If done right you will repeat OK.
You can use any part of the tool post/holder so long as you use the same spot every time.

KiddZimaHater
11-07-2012, 04:55 PM
90 Deg. Combination square set against the chuck face would be close enough for bolts.

john11668
11-07-2012, 06:08 PM
If you are going to do a few jobs like this then get a capstan attachment

rohart
11-07-2012, 06:09 PM
Using the toolholder means you have to crank the holder forwards, and back again afterewards.

I assume that you can set a carriage stop at the right that you move back to between operations. Make a hinged fitment that you screw down to the carriage that you just lift with a lever to abut the stock against when you pull it out. Let go of the lever and it drops away. Just a bit of 25mm square bar with a 10mm hole in it, and an anchor point with pivot screwed to the carriage.

Lift the bar towards you so it touches the toolholder and blocks the movement of the stock rod. Push it away and it drops down flat.

It could be a lot more sophisticated, of course.

Lew Hartswick
11-07-2012, 06:29 PM
I made a "L shaped bracket" with a few magnets that I slap against a jaw and
use that to stop the work. I guess I don't have a pix of it. :-(
BUT I do have a similar problem with using a 5C collet. Was trying to cut a
bunch of .315 +/- .003 or 4 and .515 +/- .003 or 4 using a collet in the spindle
but when the drawbar pulls the collet in to tighten it moves the work and it
doesn't move a controlled amount. Depends on how much it was loosened
to move the stock. Could cut to an extra length and use a stop and trim but
then I have to do them all again with the stop removed to drill and tap through. So is there a "trick" to keeping the stick-out within a few thou. of
repeatable using a collet?
Thanks ...Lew...

hornluv
11-08-2012, 12:20 AM
When using collets, I hold a rod in the drill chuck in the tail stock. Then I bump the stock up to that. When I tighten the collet, the stock draws back a bit so it doesn't rub against the stop. That probably wouldn't work as well with a chuck though.

Black Forest
11-08-2012, 04:07 AM
When using collets, I hold a rod in the drill chuck in the tail stock. Then I bump the stock up to that. When I tighten the collet, the stock draws back a bit so it doesn't rub against the stop. That probably wouldn't work as well with a chuck though.

I have a threading die mounted on the tailstock.

GadgetBuilder
11-08-2012, 09:38 AM
I use hornluv's method with a stop rod in the tailstock chuck but hand hold an additional piece of flat stock between the work and the stop as I bring the work up to the stop - this ensures adequate clearance when using a chuck.

John

rode2rouen
11-08-2012, 12:50 PM
Why don't you use the tool tip or tool holder as a stop? I will move the tool post to a designated dro reading and use it as a stock stop. I usually give a little extra for clean-up stock when I do this. If done right you will repeat OK.
You can use any part of the tool post/holder so long as you use the same spot every time.


Krutch,

Please, stop making sense!



Rex

ckalley
11-08-2012, 01:11 PM
I have a bed stop on my lathe that is really handy for this kind of job. It has 5 or 6 indexable and adjustable stops on it. The last time I used it, I seelcted on of the positions on the stop as my starting point, then held the carriage against the stop. I used my turning tool as a stock stop and just pushed the stock against the tool while holding the carriage in place and then tightened the chuck. It's not accurate to .0001, but more than close enough for my purposes.

Another way - If you have a DRO on your lathe, you could move the carriage to a set location that would give you the correct stick-out of the stock from the chuck and then bank the stock against a tool like I did.

Craig

Paul Alciatore
11-08-2012, 01:33 PM
I made a simple stop for use with collets but something similar could be made for use with a chuck. It mounts to the drawbar which has a fixed position in relation to the headstock: the collet is activated by drawing it back (horizontally) which results in different positions with changes in the part's diameter or the amount of tension on the drawbar. This stop holds it's position during such tightening, despite any horizontal movement of the collet.

http://img.photobucket.com/albums/v55/EPAIII/P1010002-1.jpg

Here is a link where I explain it in detail. Look for post #133 in the thread.

http://www.practicalmachinist.com/vb/south-bend-lathes/what-have-you-made-your-south-bend-147978/index7.html

There is no reason why you couldn't do something similar for use with a chuck. You would need to make a piece that mounts to the back end of the HS spindle. And it could be a lot beefier for your use: I kept it slender to allow it to be used with small collets.

Advantages: Nothing to grab and hold against the chuck or wherever. No zeroing. Just slam the next piece of stock in, tighten the chuck, and make chips. Very fast work.

Lew Hartswick
11-08-2012, 07:07 PM
Here is the fixture I made to repeat the "stick-out" for the 3 jaw chuck a few
years ago and have used it quite a few times with reasonable success.

http://home.earthlink.net/~lhartswick/2012_05_Nov%20007.jpg
http://home.earthlink.net/~lhartswick/2012_05_Nov%20009.jpg

the two disc magnets do a pretty good job of holding it but not adequate to
just slide the rod out and bang it against. :-)
...lew...

jimsehr
11-08-2012, 08:56 PM
I have made a stop out of a hinge and mounted on same tool holder as the one holding the cutting tool. Then pull stock out till it touches hinge stop then let hinge drop out of the way. Repeat. ect.
I will just set hinge on top of tool post in pic so you get the idea. You can even use a c clamp to hold hinge in place.http://i86.photobucket.com/albums/k106/jims_03/IMG_0004-13.jpg

Boucher
11-08-2012, 09:37 PM
I cut a sleeve of PVC sch 80 pipe with a cap screwed onto it. I pull the stock a little further out than needed and push it back with the sleeve then tighten the collet. Not super accurate but good enough for most applications.