I agree. My standard technique in metalworking is to go a bit oversize, and file to the dimension I want. On holes, I go undersize, like you, and file to the size I want. A set of miniature files makes the fine work a lot easier.
Originally Posted by kibble
The problem with most of those manual techniques is aligning the punch and the die well enough that we don't destroy one or the other when we tighten the vise or whack them with the hammer.
Originally Posted by Bazza_84
I did search for "sheet metal punch", and I ran into some light duty portable punches, like this $24 hand-held punch from JC Whitney. It looks very similar to this punch from BrandsOnSale.com. Neither company lists the source, but they appear to be like units from Roper Whitney, which has a webpage here showing punches and tooling, including slot-forming tooling, plus a low-cost bench-mounting base for the portable punch. This could be a pretty good alternative to hand-forming. Roper Whitney lists the price on the punch as $55, the kit with tooling and a case at $80, and the base at $28. I couldn't find a price on slot tooling, but their price for a 3/16" round punch and die set is $11.
I modified the text to show that the punches from JC Whitney and BrandsOnSale.com are NOT from Roper Whitney, but are apparently copies. There's no way to know if Roper Whitney's slot tooling will work in the knockoff tools, so it's probably best to just buy the Roper Whitney tool if we buy this to make slots. The slot tools are available from Roper Whitney distributors.**