I'm sure this is a very common issue but out of sheer interest i measured the runout of various aspects of my lathe with a baty dial indicator.
I measured the run-out of the spindle, i could barely get the dial to twitch within the smallest division being 0.01mm, so it pretty much hovered near zero, so far so good.
I put a 1/2inch bar of ground steel in the 3 jaw self centre and measure the runout from 30mm away from the chuck, it measured 0.02-0.03, not bad for a self centre i thought.
I then try my ER40 MT4 collet chuck, check the internal 8 degree taper, it runs at 0.05-0.06, slightly disconcerting.
I then move onto the same test as the 3 jaw, using a bar of ground steel measured at 30mm away and, again, the run out of the taper reflected in the bar held, 0.05-0.06mm, i'm slightly saddened, thinking i should be able to get lower runout from a ER chuck than a 3 jaw.
I can't see how i could fix this with my equipment so would anyone be willing to regrind the body of the ER chuck to get closer to 0 for a nominal sum?
The only other option i can see would be to use threaded collets directly to the spindle in future.
Michael W
Edited By Michael Walters on 26/04/2016 14:01:54