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Both a step drill bit and a knockout punch seem to be very similar, in that they both make holes in a metal box.

The step drill seems to have an advantage, since it can make several size holes using a single bit.

What are the major differences between the two?

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up vote 10 down vote accepted

A knockout punch is typically capable of going through thicker metal - at the very least, it will do it faster. A quick search easily finds knock-out punches that can do 10 gauge steel, where most step bits don't seem like they'd do well beyond 16 gauge (though I can't find anything that really says the limit).

For thin metal though, the step drill bit is probably faster, if for no other reason than the setup/tear-down time of the punch (eg, after you punch the hole, you still have to unscrew the punch).

Knockout punch:

Knockout punch

Step drill:

step drill bit

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Good explanation, but I strongly disgree with the thickness reasoning: I've step-drilled quarter inch plate with a cheap step drill from Harbor Freight, and it worked fine. So a step drill will work in "almost any thickness you're likely to encounter" The knockout punch will ONLY work in 10 ga. or thinner.... – Bob Aug 1 '12 at 14:47

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