I have a couple transitionals and maybe a wooden jack I would like to resole. What I'm about to ask is probably the dumbest question, but I just can't wrap my mind around it. I've even read a few different posts / tutorials on it and still don't get it. So as I understand it.

1) joint bottom flat

2) make new sole slightly longer than deepest iron can project.

3) glue

4) chop/pare new mouth opening.

This is where I'm really stumped. The front of the throat is easy straight down. My mind just doesn't understand how if I pare the rear of the throat following the existing bed angle how come the mouth won't just be the same size as it currently is? I mean I would be chopping to the exact dimensions which are already there, so why wouldn't the finished new mouth end up wide like it currently is?

Oh and I guess I have a second question regarding step 2, how much thicker should the new sole be, than the deepest the iron can project 1/8"?

So what am I missing?
Thanks,
Michael