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Collet Chuck Mounting And Concentricity

Arbo

Aluminum
Joined
Sep 4, 2003
Location
MPM, PA
I am in the process of adapting an ER32 collet chuck for use on a SB9A. My plan is to use a back plate for mounting to the 1.5-8 threaded spindle. My concern is with the collet chuck itself. In my mind, the registration diameter on the back of the chuck must be concentric with the collet receiver on the other side of the chuck. The chuck is of Asian quality, and it is about .006 TIR off between the registration diameter and the collet receiver. I have determined this by chucking up the threaded end of the collet chuck in a four jaw. When the collet receiver runs true, and then check the registration diameter, I get the .006 discrepancy. I am considering taking a light truing cut on the registration diameter at this point with a carbide boring bar to make sure that both readings are zero. I wanted to be sure that there is nothing I am not aware of with the ER series before making this slight modification. Thanks in advance for any insight on this. I wish to only do this once, and do it right. The first chuck I got was defective, in that the collets would not fit in the chuck at all. As a matter of fact, it is the defective chuck that I ran this test on, but I am preparing for mounting the replacement chuck when it arrives.
 
Make your back plate with a recess that the collet chuck can fit into. Allow 30 thou clearance. Install flat tip set screws radially spaced 90 degrees to provied adjustment of the chuck body to accommodate error in chuck AND collets.

Poor man's AdjusTru !!

Jim C.
 
I'm struggling with a similar situation, a different collet size...anyways

I thought about chucking up a piece of round stock for example a nice piece of drill rod in a 4 jaw, zero it, and then sliding on the collet chuck with the correct collet installed onto the round stock. (facing backwards basically with the nose towards the 4-jaw, and tighten it down)

then, true up the backside of the collet chuck and the register boss (shoulder/whatever), and make the backplate to fit, then finally cutting the backplate mounting surface for the spindle. (all this in one chucking)

Is this a dumb way to do it? I'm gonna practice first, my only concern is if the concentricity will change with different collets?)

Let us know what you did...

edit: Actually, once the backside of the collet chuck is finished, I think it can be removed, and the backplate finished on the spindle itself, and just cut and go until it mounts properly).

[ 01-25-2006, 05:43 PM: Message edited by: simplygeorge ]
 








 
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