Quote:
Then why, in the above example, do the perfs seem to line up at the outer ends and not in the center? Is that normal?
Just luck of the draw. The perf spacing from one side of a stamp to the other (and in this case, to an additional stamp) has an infinite number of positions.
Picture yourself with a pizza cutter with pins. Run that down a row of stamps to create perforations. Now use the same pizza cutter on the next row. The two rows won't line up because it's nearly impossible to start perforating at the exact same point on a sheet.
Now secure 10 pizza cutters together and run them down the rows of a sheet. Again, none of the perforations will line up from row-to-row and column-to-column because you can't get them to start punching holes at exactly the same time.
This is an over-simplification, but the premise is the same.
Russ has posted photos of perf machines in previous threads. It would be worth taking a look.
Brian