Originally Posted by
PhoenixMetal
My punches are not especially long - they're only 2" long (with the pilots being a little longer) which is around as short as they come, not including the extra stubby ones used in special situations.
So given a situation where the dowel pin locations are closer to a punch than the radius of the toolholder, even with short 2" punches, you'd need a really long drill to clear everything (for example, 2" punch height + 1.5" die shoe height = 3.5" worth of drill sticking out of the toolholder. I'm generally using 3/8 dowels, so for a drill bit that's less than 3/8", that would require an unusually long drill. Your suggestion to just get the drill through sufficiently far into the die shoe to establish location and to finish the hole later with the punch holder removed is good advice which I am sure I will use in the future.
This may be getting off topic slightly, but you mentioned the use of other alignment methods when a design calls for very tight clearances. On one of my first dies, I was working with 10% total clearance on .024" material (0.0012" clearance per side). I was having issues with punch tip breakage because my alignment was not perfect and the punches were having to force their way into the die buttons instead of sliding right in. What sort of special techniques or machines would you use given the requirement of very tight tolerances?