A little logical thinking
Looking at the shape of the botom of the bit/chisel combo what do I see?
Mirror image of bottom of hole

Are both bit and chisel are cutting clean?
Yes, guess that means both are sharp.

Which part of the bit/chisel combo is cutting 'ring'?
Its happening around the edge of the bit.

So how can I reduce it?
Reducing the bit clearence will reduce ring

Can I expect to get a perfect square, flat surface fron a circular motion?
Round pegs do not fit round holes.

You have 2 options
Drill mortice a little deeper and allow tenon to rest on ring.
Or
chisel out botom of mortice by hand.

"David" cosmosatnointerbaunspamdotcom wrote in message
...
Hi folks,

I'm using a General mortising machine and I'm wondering if this is what I
should be getting
as a mortise?

I've adjusted the chisel and bit with the .40c method and tried a few
variations but I still end up with that little collar
at the bottom of the mortise.

I've sharpened the chisel using the Lee Valley cone sharpeners, I've
gently tuned up the bit so that it is sharp.

http://i13.tinypic.com/2z7pmab.jpg


Anyone have some suggestions as to what I might try to correct this?

I hope the picture is of sufficient detail.

Thanks for your time,

David.