So first the gloat. I made my first bad ass mortice and tenon joint
today. Bad ass meaning perfect, square, tight, ya know perfect.
Considering the mortice was through three inches of african teak, three
inches in length, and using my inch reg mortice chisel I am pretty
happy with the whole affair.

So the question. I think a big chunk of the success of this joint is
due to my new fancy Lie Nelson Rabbet Block Plane. It rocks, and is on
sale at woodcraft this month. So finally the question, when I tighten
down on the brass screw to lock the blade in place it frequently skews
off the the side. It seems to be square ground, so I am thinking that
it isn't intentional. Am I wrong about that? I am able to get it to
line up straight but it takes quite a bit of playing around, something
I wasn't expecting. Is this user error? User ignorance? Or something
afoul with my new toy?

Thanks