I can attest to draw boring being a common, perhaps standard practice in historic frames in Maine. Quite often you can see the layout marks for the hole on the tenon scratched onto the tenon just like all of the other layout marks were scratched onto the timbers with an awl. I believe that if the holes were misaligned too much they would reduce the size of the pin to avoid straining the tenon relish or pin too much (doesnt that give an engineer the willies!). Some pins come out of old frames cracked but it is hard to tell if the strain was from building movement or just too much strain in the draw bore.
Jim
