Bob,
I don't know where you got your accuracy numbers, but all of my 3 jaws are accurate to less than .001". Keep them clean and oiled
and don't over torque them and they are accurate enough for 90%+ of your work.
Steve

"Bob La Londe" wrote in message ...
From the Sherline website.

"Due to the nature of the design of a 3-jaw chuck, it cannot be expected to run perfectly true. Even 3-jaw chucks costing five
times more than the one made for this lathe will have a 0.002" to 0.003" runout. If perfect accuracy is desired in a particular
operation, the use of a 4-jaw chuck or a collet is recommended. Both are available for your Sherline Lathe."

I don't have a Sherline lathe, but I was considering mounting a small Sherline chuck on a stepper driven spindle for a fourth
axis on one of the mini CNC mills in the shop.