[eliot15]

Hi,

I've been setting up my first couple of turn/mill jobs lately, and was just looking for some feed back on setting chuck jaws.

Is there a "rule of thumb" out there for deciding where on the chuck to set your jaw? How do you know when you are clamping enough, but not too much? Sort of like "close the jaws until the part just fits, then close them one more tooth." Or two more teeth, or whatever.

Do ya' see where I'm going with this?

Thanks

[Geof]

Are you referring to a hydraulic chuck?

Go about the other way. Open the chuck and position the jaws so you can just get the part in.

The clamping force is controlled by the hydraulic pressure not by the jaw position.

[fizzissist]

Also note if there are marks on the face of the chuck indicating, if it's hydraulic as Geoff points out, that show the range of clamping motion. That is, the indicator on the moving master jaw, usually #1, that should be within the 2 lines when clamped, either ID or OD.

It's probably a range of .06-.09", and assures you've got proper clamping force according to the pressure you've got set for the job.

(you were wondering what those weird little lines were for?? )

[eliot15]

Thanks for both replys.

Yup, its a hydraulic chuck on a PUMA turn/mill (2000 SY). I'm a mill guy, so this hybrid lathe stuff is new to me, but I like it. I'll look for the weird little lines.

The sub chuck is clamping on the ID after a part transfer. So I guess the ID correlate to Geofs point is: close the chuck and position the jaws so you can just get the part over the jaws. Thats what I did today on the sub chuck. Then I moved the jaws in 1 extra tooth just for a little more clearance ('cause I'm a coward). Probably didn't have to, but the sub chuck has to travel on the B axis over to the main chuck and grab the part, and I just wanted to make sure its got plenty of room.

On the main chuck, I'll just try the "open the chuck and position the jaws so you can just get the part in" approach.

Last time I ran this job (the first time), I seemed to have some problems with jaw pressure. Parts came off a little out-of-round. I was thinking of looking into maybe backing off the hydraulic pressure a bit.

Thanks again.

[fizzissist]

Little trick for ya....

For clamping on an OD.... with a boring bar positioned at the diameter of the OD you're clamping on... Close the chuck and run the tool tip up towards the chuck, and place one jaw in a position so that the boring bar tool tip is just touching the clamping portion of the jaw.

You now have a relative location for the jaw,,,, but,,,, Since the master jaw travel has gone to it's limit, and beyond the allowable clamping range, move the jaw in one notch. Mount the other jaws in the corresponding notches, and you're on your way.

Another hint,,,, for repeat parts with soft jaws, scribe a reference line on each jaw that aligns w/ some feature on the chuck body, and then you can just slap 'em on and go!

lemme know if this doesn't make sense!

[eliot15]

Thanks for that. I'll store it away.

[tanvon]

hi, I really enjoyed this all discussion. When I set jaws on my hydraulic chuck cnc machines I do the same, just take the jaws as much near the job as possible then I tie them there.