Well, hate to dredge up an old thread, but this seemed like the most appropriate place to post this.
I bought one of the BOSTAR 5C collet chucks for my lathe with the D1-4 interface. I went with the BOSTAR because they were relatively inexpensive, and I figured any company that would put their name on a Chinese import would at least make sure that the merchandise wasn't besmirching their reputation due to lack of quality or by not matching the manufacturer advertised specs. Silly me.
The guy I have been conversing with when I found that the 0.0006 TIR was a fantasy, as I am getting more like 0.0065 TIR, has been good enough about it, and has offered to take back the chuck and the collets I bought from him without any hassles. He said he even spoke to the manufacturer and is supposed to get some sort of test jig from them, albeit not for a few months. He said he does not test them, just imports them and sells them. So much for my theory on a "name brand" being better than a no-name Chinese import. On the Ebay auction page for this item, he shows something like 1580 sales of this particular chuck, and has a 100% rating, so heck, I figured this was going to be a relatively safe bet of getting something decent. Again, silly me. I wasn't expecting perfection, just decent would have been perfectly fine for me.
Anyway, I took a video of my checking runout off of most of the surfaces, and tried the three different mounting position options offered by the D1-4 camlocks, all to no avail. If you look close, you can even see the wobble of the nose assembly itself. The inside surface of the nose for holding the collets was certainly no better.
The guy doesn't seem interested in me trying another one, so I am guessing he doesn't expect a replacement to do any better for me. I've been asking around to other suppliers and even had one tell me flat out NOT to buy the chuck from him, as he prefers to only deal with professional machinists. So I guess that his ad copy quoting a TIR of 0.0006 is just a pipe dream too, and the people buying such chucks need to fix them to bring them to that spec. So I guess "DIY to get 0.0006 TIR" would be a more accurate claim.
Ah well, only reason I wanted to buy this thing was to be able to use the 5C collets for square and hexagonal stock. I already have an ER40 collet setup for round stock, plus the regular 3 and 4 jaw chucks, so no big deal sending it all back, I guess. Just another "good idea" that went south on me.
IMHO.
