I bought some Chinese BT30 and BT40 ER32 collet chucks off eBay a while
back and was pleasantly surprised by how accurate they were. The finish
looked good on all surfaces. I bought one before buying the rest and
measured the bore when fitted in the spindle. My tenths dial gauge
hardly moved. When I got the rest they were all pretty close. The nuts
on the BT30 chucks are a pain though. The bit that locates in the groove
on the collet is concentric instead of being offset. This makes it a
real pain to get the collets back out. Those ones are for my router and
will spend most of their lives with 1/2" collets so I'm not that concerned.
Les
There are a few reviews of Chinese collet chucks on youtube. The two
I've seen measure chuck internal taper runout similar to your
experience, Gene. (The outside's OK, but the bit that counts is poor.)
Once one of the Chinese collets is inserted, all bets are off, and it's
best for woodworking.
One review showed one of the ostensibly ER32 collets in the set was over
33mm in diameter, and couldn't be inserted in the nut in half a minute
of wrestling.
Another video shows a Chinese collet chuck's internal taper being
ground. Nowhere have I seen anyone use one as-is.
It appears to be best to remember how _much_ cheaper they are, and then
consider why. I wouldn't buy 'em, except as a kit to grind to tolerance,
chucking out the collets beyond rescue.
To attempt a rescue, maybe skim the chuck internal taper, then hone it?
The chances of making it worse are slim. If it works well, there's a
very handy youtube video in it.
Erik
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