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Step drill bit.
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Previously:
https://www.homemadetools.net/forum/...132#post199439
https://www.homemadetools.net/forum/...176#post188084
https://www.homemadetools.net/forum/...474#post185601
https://www.homemadetools.net/forum/...663#post182618
https://www.homemadetools.net/forum/...213#post149939
My preferred tool for drilling ROUND holes in sheet metal or other thin stock - material where a conventional drill usually produces a triangular hole.
I paint the cone step just above the one for my desired size with layout dye so that, in the heated excitement of drilling, I know where to stop pushing the drill.
I love step drill bits! As Marv said, these are what's preferred for making truly round holes in thin metal. They also make nice round holes in thicker material if you have step drills with longer steps.... I've got one that is for 1/4" thick material, up to 1/2" in diameter. I also have others that are the more typical 1/8" steps, and go up to 3/4 and one that's up to 1-3/8" diameter. I have a few in metric as well.
For drilling aluminum, if you have a lot of holes to do, lubricate the bit with WD-40 frequently, as that keeps the aluminum from galling up and keeps the chips moving.
I have had pretty good success with ones from Harbor Freight as long as you don't abuse them. They are easily half the price of name brand ones like Irwin, etc.
I have one that has the sizes of conduit knockouts, sometimes much handier than using my Greenlee knockout punchesQuote:
Originally Posted by KustomsbyKent
A step drill is good for chamfering and deburring holes. One huge step drill can cover holes from 6-60mm.