I think I've figured it out but I thought I'd ask just to be sure.
I am placing some false thru tenons in the top of a small cabinet I am making and am, or was, having trouble with my chisel technique. I first roughed the width with a router ( a non hand tool for your primitive types) and am squaring the ends using a marking tool to define the width and length of the mortise. I have found that the concept of chiseling on the mark line compresses the fibers of the wood making the end of the mortise look slightly dovetailed.
I then found that if I sneak up on the mark, taking slight cuts, that the compression was minimal.
The end cuts were easy as even if the wood compressed a little I could just lengthen the tenon. Also it seemed that the end grain didn't as easily compress.
I hope that the above is explainitory enough to get the idea what I am doing and what I have discovered. I think this is the correct way to finish and define mortises.
The chisels are sharp as I am not having any trouble cutting the end grain fibers in hard maple.
If anybody has any other technique that is easier or more of a traditional way of doing what I am trying to accomplish please chime in.
Thanks--------------Jim