Bob La Londe wrote:

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.

The Adjust-Tru chucks have provisions to allow them to be adjusted to
run true, but I expect that trueness only applies at the particular part
diameter that they are adjusted for.