Setup for grinding an ER32 collet chuck

[Okapi]

Hi Christophe,
A good idea to use this way, and to make this video, it is a situation very commonly found with inner conical parts, often the broach cone with W20 is damaged and need such a solution.
Have a nice day.
Pierre

[Paul Jones]

Hi Christophe,

I would not have thought of using a wood lathe but with the excellent precision in the spindles, the technique produced excellent results.

I had a similar situation with a hardened steel ER16 collet chuck I bought on eBay for my 3" swing Unimat and discovered it had 0.003" (0.076 mm) TIR. I decided to make my own ER16 collet chuck. I initially created the chuck using my 12" swing geared head lathe and then finish grinding it on the Unimat SL 1000 (see for the grinding http://www.homemadetools.net/forum/u...6880#post67090 and the first version without grinding at http://www.homemadetools.net/forum/e...0273#post57039 ). I measured the ground TIR at 0.0005" (0.013 mm) with an almost new collet and gage pin and was pleased with the results (the TIR on the inner surface of the collet chuck was 0.0001" (0.003 mm) but it is the combined collet and chuck TIR that is important).

After the success with the homemade ER16 collet chuck, I used the Unimat grinding technique on the chuck bought on eBay. I was surprised at the improvement to be TIR of less than 0.001" (0.025 mm) but it took too much grinding time to remove the hardened steel from the commercial collet chuck for this level of TIR as compared to just making the collet chuck from scratch.

Regards,

Paul