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kenrinc
08-12-2011, 06:53 PM
Got this baby mounted. Saw all the previous posts about issues that might arise. Mine had a rise or "pip" in the ground outer flat surface that mounts to the backplate and the inner flange was out as was noted by others. Now that I've got it mounted I'm seeing what I want to see "at the chuck". As I move out say 2" I see something totally different. This is my first use of 5c collets so should I be expecting something better than that, that far out? FWIW I'm testing using a ground rod that I know is straight.

Ken

gwilson
08-12-2011, 07:15 PM
What kind of ground rod? Drill rod is not accurate for really critical measurements. It tends to have "lobes"on it.

I use the shank of and end mill when I want to check the run out of a chuck.

kenrinc
08-12-2011, 07:33 PM
It's a piece of ground micro-grain carbide rod 1/2" in dia and 6" long. I keep it in a box just for testing.

Ken

lakeside53
08-12-2011, 10:15 PM
"Mounted to backplate" Did you turn the backplate on the lathe it's mounted to?

Edwin Dirnbeck
08-12-2011, 11:16 PM
I would remove the collet from the collet chuck.Then useing a last word style indicator, indicate the tapered hole in the collet chuck about .3 deep then the srtaight hole about 2.1 deep. These are the precision ground areas that locate your collet.They should be running deadtru.Also use a telescope gage to measure the rear hole and compare it to the straight o.d. of your collet.It should aprox.001 larger.If both diameters run true and the rear hole is not to big and sloppy then you might have a bad collet.DANGER when indicating the straight hole dont break your indicator point on the little key. Good luck, EDWIN

kenrinc
08-13-2011, 04:44 AM
The collet mounting area where the 5c angles meet seems to be dead nuts. When I measure the actual mouth area of the chuck it measures .0005 tir. Which is what the ground rod measures at the chuck. Once I measure out 2" or so it's .004" tir.

The backplate measures out at .0005 same as the lathe spindle. Logan 10.

Ken

daryl bane
08-13-2011, 09:12 AM
What brand of collet are you using? I didn't see that in the post? Try a known good collet, Hardinge preferred. I find that cures most of the runount problems.

kenrinc
08-13-2011, 02:44 PM
It's the CDCO 5c asian chuck. I took it off the backplate again just to check everything and the backplate measures same tir as the spindle. With that out the way I bolt up the chuck and since I made the register slightly smaller on the back plate, I tap the chuck in using a collet and the ground rod. All the other collets seem to be right on as the others but with the tir going to .004 2" out from the chuck I'm wondering if the chuck isn't wobling. Colinear? Since I'm guessing the carbide blank is damn if not perfectly straight.

Ken

lakeside53
08-13-2011, 07:25 PM
If you've tried a quality collet and the problems still exists, send it back. The back of the chuck is probably not correct with respect to the collet bore. To test this theory, you could try inserting a couple of "really thin" shims near a couple of the bolts to counter the excess tir

Mcostello
08-13-2011, 09:45 PM
I have the same chuck with the same problem. I bought one chuck with the same problem. Sent it back.Next new chuck had same problem,I re-turned the tapered part. Problem persisted in varying amounts with different collets. Took apart the chuck to find chips underneath the plate the collet screws into. Cleaned it out with no further problem. Wish I would have done that first.

kenrinc
08-13-2011, 10:47 PM
Mark, how did you get the chuck open? I see the bolts on the underside but I don't see any seam where the chuck actually opens. Maybe the ground over the seams so you can't see them?

Ken

J Tiers
08-13-2011, 11:34 PM
I suppose it is worth mentioning that this is a COLLET chuck......

You ARE, I assume aware that a 5C collet grips the part over a length of about a half inch, more or less.

So...... what's this about 2" out??????

That's out 4X the length of the collet grip......

Collets are for close to the chuck work..... not for large "stickouts", which are a bad idea anytime, but may be worse with collets than regular chucks.

Davo J
08-14-2011, 05:16 AM
I have read of a few guys around that have reground the taper after setting it up on a back plate to get it to run true. From then on it is spot on.

Dave

kenrinc
08-14-2011, 05:54 PM
You ARE, I assume aware that a 5C collet grips the part over a length of about a half inch, more or less.

So...... what's this about 2" out??????

From my original post.....


This is my first use of 5c collets so should I be expecting something better than that, that far out? Ken

Thought I was pretty clear. Thank you for answering the question.

Ken

kenrinc
08-14-2011, 08:15 PM
Fixed it. Mark tipped me off. I figured out how to take the chuck apart. Good thing: it was nearly black inside; like it had been assembled in a coal fired power plant. Removed and cleaned everything. It was spotless when I was done. Regreased, bolted it to the backplate and low and behold .0015" tir 2" out from the chuck. Double checked with another collet and it's good. I'm happy. I realize (now) that this is no different than any other chuck in terms of "stick out" of a long rod but I felt that the issue was more one of the chuck itself. It looks as if the 5c tightening mechanism was throwing the collet a bit sideways.

Thanks

Ken

Mcostello
08-14-2011, 08:42 PM
I did not see how it could bias the collet either as the collet seats on the taper, but it works now and it did not work before the fix.