Countersinking with a too-fast drill press

Joseph Gwinn · 2005-11-23T23:55:02+00:00

In June 2005, I was having problems because my little 12" Delta variable-speed drill press has a minimum speed of 500 rpm, which was a real problem, especially when countersinking.I had found an interim solution for larger holes: Put the countersink in the hole and turn power on, releasing the downward pressure before the press gets up to speed.This did not work with small holes, and the 1/4-inch severance countersink, working in 6061 aluminum, flooded with a water-based coolant. I would have thought that a small countersink would be OK at 500 rpm, but the holes became ragged and misshapen.Countersinking with a hand drill did work, making pretty holes, but yielded inaccurate countersinks because it's so hard to drill straight by hand.I was busily tearing metal and hair when it occurred to me that tapping is an extreme kind of machining, and yet one can get clean threads, with the right lubricant. So I tried LPS Labs' "Tap-All". It worked, even at 500 rpm. Haven't tried it in steel and/or for large holes yet.Joe Gwinn

Nov 23, 2005 22 Replies

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Joe AutoDrill 20 years ago

What about the Delta 70-200 and/or 17-968?

I'm almost sure the 70-200 has one (might be a discontinued model) and a customer of ours just bought a large number of heads for 17-968's and told us it has a MT... I sure hope he is right!!!

Anyhow... Maybe one of these will work for you?

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Joseph Gwinn 20 years ago

Hmm. I don't recall seeing these before on Delta's website, but I'll look again. Actually, I wasn't looking at 20" units then, and that may be the key.

Delta 70-200 looks possible. It's a 20" metalworker's drill press. It has a MT-3 to J33 adapter, with a J33 chuck, and a T-slot table. Min speed is 150 rpm. The drive is step pulley, 110/220, single phase. Single phase. Wonder if it also comes in three phase, so I can implement variable speed using a VFD. Switching belts on pulleys is pretty slow.

Delta 17-968 is a 17" woodworkers unit, and so has the wrong kind of table, and a single-phase motor. However, it has the same MT-3 to J33 adapter plus J33 chuck.

Delta 70-200 is still listed at

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, and three phase appears to be available. Don't know how I missed it. Hmm.

Thanks,

Joe Gwinn

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