How does one make clean round holes in sheet metal

[Snort]

How would one go about cutting 1/4 inch, 1/2 inch, 3/4 inch sheet metal holes in a way that will make them round, clean and without distorting the adjoining metal? Are there special hole knockouts one can buy, or mini-hole saws?

[zeroman]

I use a step bit.

No problem. No distortion, easy to clean up any sharp edges with a round file.

They're rather expensive, but since 2-3 sizes will get you from 1/8"-1"+.. Its not a bad investment. My neighbor did a pretty good job cutting 2 inch holes in a hood (on the curve) with a hole saw. Didn't even scratch the paint around the hole. He's fairly meticulous.

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77 super convertible

[Snort]

That looks pretty nice, it reminds me of one of the characters on Sonic the Hedgehog that burrowed through the ground.

[zeroman]

[swhitcomb]

Bought mine at harbor freight. Not expensive there at all. $15 for a set of 2, including one that goes to 1 1/2".
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My 71 Ghia Been in my family since 1980
My Patina 66
My 74 Ghia
07 Boxster

[Foxx]

http://electrical.about.com/od/electricaltools/a/knockoutpunches.htm
these work too,.. good to have if you expect to make a lot of holes, or are an electrician.

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Frank
OG JHC
59 panel




Sarcasm is the body's natural defense against stupidity. i seem to use a lot.

[Chris Hollaway]

I have both and they both work great.

[zeroman]

i would guess that the knock out punch has to be on flat or nearly flat metal to work properly.
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77 super convertible