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View Full Version : Bad TG-100 collet chuck?



lbhsbz
02-25-2011, 06:31 PM
I bought a Kennametal TG collet chuck to replace the 6 ball chuck on my valve grinder....having some problems with it. The chuck spins in plain bearings on the machine and the bearings are slit so that clearnance is adjustable.

I did this improve workpiece runout. Problem is, I'm still getting about .002" TIR in the workpiece which is held but the collet chuck.

indicator out:

I've got 0.0004-.0005" of runout in the taper. If I measure runout in the chuck shank itself I'm at 0.

If I measure runout on the OD of the business end of the chuck, I've got about 0.002".

Seems strange...runout at 3 different spots on what I feel should be a precision ground piece show up different results....and all are repeatable.

I imagine there is some error in the collet itself as well, and stacks up to be excessive in the workpiece.

I called Kennametal and they said "it's within tolerance"..

...and since I already modified it a bit to fit the application (small keyslot) I can't return it. I'm not really concerned about this aspect...I'm not new to throwing brand new junk in the trash and throwing more money in the toilet, but I'm wondering if this is the norm or should I expect better concentricity and TIR while using a ER/TG type collet setup?

beckley23
02-25-2011, 07:08 PM
If that's within tolerance for Kennamatal, then they better count on losing customers.
Harry

Black_Moons
02-25-2011, 07:18 PM
Sounds like you need to find someone with a lathe + toolpost grinder.

And in the future, Slap chucks you buy into your mill or lathe (Via collet? or however you can get em in) and check for runout before modifying them.

Though its kinda sad you'd need to do this with a kennametal one, I can see why you would just expect it to be made correctly..

lbhsbz
02-25-2011, 08:51 PM
I can see why you would just expect it to be made correctly..

Why's that? Nothing else that I pay good money for is made correctly...why should this be any different?:D

Seriously though...I would think Kennametal could hold better concentricity with their equipment than I could on my 70 year old worn out lathe. Fixing it would be a good trick...I'm not sure what I would indicate off of to center it. None of the business end surfaces are concentric with the shank.

Lesson learned...check it first.

Jim Shaper
02-26-2011, 07:32 AM
Have you checked your collet itself? They do get damaged and wear out.

At work, we use ER11's in swiss machines, and to hold .001" tolerance in the part with drills, you often need to play with the rotational orientation of the collet in the holder. They've held nothing but carbide drills all their lives, but like I said, they do wear out.