"David" cosmosatnointerbaunspamdotcom wrote in message

These 1/2" mortises are to receive 1/2" square metal spindles which will
not seat on the bottom of the mortise because of this ring.

OK, that is a slightly different appliction than the normal morise and tenon
construction. Generally, the hole is deep enough that there is a bit of
clearance and the holding is on the sides of hte joint. In your case, you
either have to clean them out or go a little deeper if the fit is that
precise.



I didn't expect to have a flat bottom but I expected that if I drilled a
3/8"- 1/2" mortise I would be able to sink them that far.

From the picture I posted, is this what a mortise machine mortise is
supposed to look like, thin ring (collar) and all?

The setup is perfectly normal. You'll have to adjust the stroke for your
application if it is that critical. With wood, it is not. The construction
of the bit and chisel won't allow you to get much better than what you have,
but some playing around may reduce, but not eliminate, the collar.