Need Help!- Need help with Set-Tru chuck centering

[dpseafish]

Hi:

I'm a new member, and a real novice at lathe work. I have a 1982 South Bend heavy 10 lathe. With it I got a practically new Bison D1-3 Set-Tru 3 jaw 6 1/4" chuck, but no instructions on how to center it. I have a piston wristpin in it and the dial indicator shows a total runout of about .009. How do I center it?

There are four machine screws holding the chuck to the base plate, and on the side of the assembly there are three screws with square holes to tighten the chuck and four more with hex sockets (really two pairs; they are not equidistant from each other). I am reluctant to mess with it without knowing what I am doing.

Help!

Thanks!
David

[cam1]

No worries:

the 3 square holes at 120 degrees are to open/close the jaws.
The screws on the face "suck"it against the adapter.
The 4 screws on the periphery sre set against a shoulder to allow you to adjust the chuck true to a set diameter.
Here's how to set it true:

1) get a ground pin, or machined pin close to the diameter you will be chucking.
2) insert into chuck jaws and tighten.
3)using an indicator, check the runout on the OD of the pin.
4)If it's not what you require, proceed with next steps
5)loosen the 4 machine screws on the chuck face a little bit.
6)with pin in chuck jaws, indicate on pin OD, and adjust 4 setscrews on chuck periphery, until runout=0 (adjust 1 screw, then adjust screw @180 degrees opposite)
7)Carefully snug up the 4 screws on the chuck face.
8)re-check runout on pin OD.
9) if OK, you have set the 3 jaw chuck to run true to the diameter that you chucked.
10) repeat if not satisfied.

regards

[One of Many]

Originally Posted by cam1 No worries: the 3 square holes at 120 degrees are to open/close the jaws. The screws on the face "suck"it against the adapter. The 4 screws on the periphery sre set against a shoulder to allow you to adjust the chuck true to a set diameter. Here's how to set it true: 1) get a ground pin, or machined pin close to the diameter you will be chucking. 2) insert into chuck jaws and tighten. 3)using an indicator, check the runout on the OD of the pin. 4)If it's not what you require, proceed with next steps 5)loosen the 4 machine screws on the chuck face a little bit. 6)with pin in chuck jaws, indicate on pin OD, and adjust 4 setscrews on chuck periphery, until runout=0 (adjust 1 screw, then adjust screw @180 degrees opposite) 7)Carefully snug up the 4 screws on the chuck face. 8)re-check runout on pin OD. 9) if OK, you have set the 3 jaw chuck to run true to the diameter that you chucked. 10) repeat if not satisfied. regards

Nice write up Cam1

Just to add a little detail to the process above for the less initiated. Not better, but may add some comprehension in doing this quickly.

There is no better chuck for rework and repair than a set true. A 4 jaw will do, but the part shifts around too much while getting it aligned.

I use a dial test indicator but a travel indicator would work.

6)with pin in chuck jaws, indicate on pin OD, and adjust 4 setscrews on chuck periphery, until runout=0 (adjust 1 screw, then adjust screw @180 degrees opposite)

With the indicator set some where between 10 and 12 O-clock on the test piece OD. Find the highest point in the runout. Now sight an imaginary line from the OD of the chuck, through the point that the indicator is touching to the center line of the spindle axis. Observe where the "set true screws" are at in relation to that imaginary line. Loosen the closest one a tad and mental note the indicator needle position. Now rotate the chuck 180 and observe the total difference on the indicator, and tighten this opposite screw now pointing at you 1/2 that reading. REPEAT and rinse until all runout is gone to your satisfaction.

Usually within about 4 tests, you can have it running true at the position of the rod being checked. Keep in mind, you may want perfection, but if the part being trued is not round, split the differences and call it good-nuff. Another fact in truing a chuck. It will only run true for the diameter being gripped. Do not expect other size bars to run true. Slight deformations in the scroll shift each jaw. Abused chucks are worse for this, but even new chucks need checking when the grip diameter will be used untouched, but critical to the part function.

Further more, for a new chuck. I wouldn't blindly trust the jaws or the mount as it fits your lathe nose compared to the factory running alignment. At least check it out for your own peace of mind. First indicate in the OD of the chuck body true. Then compare this to a ground test rod gripped in the jaws for runout. Check the rods runout near the jaws and 4-6" out from the jaws. If the runout is greater than .003 and worse as you travel away, I would grind the jaws true to the chuck body centerline as it is mounted. The mount should have an arrow or a zero marker so it is mounted in the same position each time on the spindle nose. If it is missing, add your own at the time the jaws are ground in place on the lathe. If you do not have the capability to grind, beg, buy, borrow or steal a set of soft jaws in the same config as your hard jaws. Mill and turn them to suit. I won't go into all the details of grinding or turning soft jaws. There are plenty of those procedures to peruse as needed.

For 3 jaw secondary operations or reworking of a part that needs to be cleaned up with minimal material removal or mod'ing features. Grip the part in the chuck and align its face or 2 ends of the bore to set the part true to the spindle centerline first. Using known good surfaces that have the least amount of wear or use selective reasoning of the original machined surface. Say a step or a grove or the end face, flange etc. Once the part is confirmed parallel to the spindle axis, then use the set-true screws to bring the OD or ID on center as detailed above. Again, the idea here is slelecting the best surface alignment reference that everything else on the part needs to be true to.

If all else fails. The best plan to keep a turned part true, is to turn all accessible features BEFORE the part is parted off. Secondary operations for OD work can be completed on another part(like a spud, mandrel or shank) turned to size regardless where the runout of the chuck is at, within reason.

A little ingenuity can always add to your bag of tricks, but a set true chuck is a must. I couldn't afford them for my home shop, so I've modified a few to set true function on the cheap.

DC

[cam1]

Hi DC:
Thanks for expanding the description, my wife always tells me that I go into too much detail. In this case the pendulum swung the other way....

regards

[One of Many]

Originally Posted by cam1 Hi DC: Thanks for expanding the description, my wife always tells me that I go into too much detail. In this case the pendulum swung the other way.... regards

It's only too much information when one already knows what they're doing. I've seen trainee's mess around indicating a part in, ripping their hair out, while stressing out over nothing. The uninitiated like more information than they need, to grasp the concepts of runout/alignment correction and benefits of using a set true chuck.

Once these concepts become second nature, the same alignment procedures can be applied to any machining operation and workholding a part in 3 planes. The desire for flawless results, starts with the most reliable setup for success. Recognizing a bad setup before the cutter hits the part isn't always obvious to the beginner. Common sense takes exposure and experience, in order to make it common in their world.


DC

[cam1]

I agree, with one twist:
We have an apprentice (1st year), I always get him started with the required background info (and showing him how and why), but sometimes I let him chase his tail a bit, so that he learns how to deal and adapt to the everyday problems that arise. Don't get me wrong, I'm always there to help, but I found that too much info can create an environment where people resort to asking first, before trying thinking it through. I always ask him to show me the setup before he turns the spindle on.A good example is chucking work in a 4 jaw, even with a good description, and showing how, it still takes a while to ramp-up to the skill (that's OK). One of the things that I'm still learning, is not to get frustrated with myself when I'm faced with the day to day problems encouneered in the shop.

regards

[One of Many]

Originally Posted by cam1 I agree, with one twist: We have an apprentice (1st year), I always get him started with the required background info (and showing him how and why), but sometimes I let him chase his tail a bit, so that he learns how to deal and adapt to the everyday problems that arise. Don't get me wrong, I'm always there to help, but I found that too much info can create an environment where people resort to asking first, before trying thinking it through. I always ask him to show me the setup before he turns the spindle on.A good example is chucking work in a 4 jaw, even with a good description, and showing how, it still takes a while to ramp-up to the skill (that's OK). One of the things that I'm still learning, is not to get frustrated with myself when I'm faced with the day to day problems encouneered in the shop. regards

That is oh so true in the shop where help is to readily available that can become a habit for trainee's relying on others experience rather than on their own accord.

Here the difference is, many of the ameture home shops have limited access to that expertise first hand. I cannot tell you how many times in writing a procedural description, I have recieved responses where in the reader is lost in confusion without including visual perspective to the process. Some of that is lack of exposure and comprehension in reading and applying it. It may not serve everyone, but my effort is to influence the least of these. Not to be critical of yours.

Right you are, Experientia docet.


DC

[Geof]

Originally Posted by One of Many ........ I cannot tell you how many times in writing a procedural description, I have recieved responses where in the reader is lost in confusion....DC

I am glad to know I am not the only one to lose people in the details.

And when I read through both posts I couldn't help thinking that for a truly complete description nothing could be omitted. Then I thought how quickly it is possible to perform the procedure with experience; it seems sometimes the longest explanations are needed for the shortest operations.

[cam1]

DC:
See you in the next post.

regards

[One of Many]

Originally Posted by Geof I am glad to know I am not the only one to lose people in the details. And when I read through both posts I couldn't help thinking that for a truly complete description nothing could be omitted. Then I thought how quickly it is possible to perform the procedure with experience; it seems sometimes the longest explanations are needed for the shortest operations.

Vague or verbose. Damned if you do, damned if you don't?

Try writing an operator manual in Braille!

DC

[cam1]

DC: Good point, I remember having to write an instruction on how to sharpen a pencil in college (technical writing), and that taught me that even the most basic tasks that we take for granted can be daunting for someone who has never tried it.....

cheers