Undercutting A Drilled Hole

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Undercutting A Drilled Hole

Post by rexcsmith » Wed Jul 06, 2016 11:25 am

I want to undercut at several levels in a hole I'm drilling. It's a 3/8" hole in mild steel. Every 1/4" through the hole, I want to cut a round slot that is about 1/2" in diameter. I don't know if this is possible nor can I visualize what kind of tool would be required to do it. Any knowledge on this out there?

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Re: Undercutting A Drilled Hole

Post by david5605 » Wed Jul 06, 2016 2:17 pm

Do a Google image search for a internal snapring grooving tool and lots of images will pop up. One style looks like a keyway cutter. Another style has some of the shank cut away to give you relief so you can offset the cutter once you have it in the bore.

There are various YouTube videos on the subject too.

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Bill Shields
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Re: Undercutting A Drilled Hole

Post by Bill Shields » Thu Jul 07, 2016 7:21 pm

if you can mount it in a rotary table, with the hole on center, you can do it with a woodruff key cutter.

or if you have a 'facing head' for your mill, you can do it that way.

or you can go on center, then linear move off a bit then circle around and return.

do you have a CNC mill or are you building one?

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