Hello,

I'm hoping someone can help me figure out a problem.

I recently bought an ER40 MT3 collet chuck from a seller on Ebay, for my Micromark 7x14 mini-lathe.

Shortly after that, I bought a set of 23 ER40 collets from another seller on Ebay.

I installed the collet chuck into the spindle - and played around with it a little bit until I measured a runout of about 0.0003" (on the inside tapered surface of the collet chuck).

Then I installed the 3/8" collet from the set, and into that I inserted a 3/8" drill rod that I know to be reasonably straight.

The runout was about 0.0009" (measured right in front of the chuck), but the 3/8" rod was canted; IOW, when I tightened down the nut, the 3/8" rod tilted a little bit, and at a distance of about 4" from the chuck, it's off (radially) by about 0.005".

With the collet nut tightened down, I can see that the front face of the collet is not parallel to the front face of the nut.

How can I tell if the problem is the collet chuck body, the nut, or the collet?