Cool Step Drill for Electrical Knockouts

M

macardoso

H-M Supporter - Silver Member
H-M Supporter - Silver Member
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I've been doing electrical panels for years and have tried all kinds of different tools (hole saws, step drill sets, greenlee punches, trepanning cutters, jig saw, etc.) to make cutouts for electrical connectors and trade size fittings. I've found them all to suck other than step drills, but I found them to be very expensive and limited in range.

I just picked up a new step drill from AutomationDirect for $55. Pricy, but it drills its own pilot hole and goes up to 1.375" (1" trade size) with major steps at 7/8" (1/2" trade size), 1.125 (3/4" trade size), 1.218, and 1.25. It also has minor steps at 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", and 11/16". Split point, HSS, and helical ground flutes. I think this will be the last knockout tool I buy for a long time.

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Having used one of those for years, I draw your attention to the "odd" size of 1-7/32 inch. I think it is 30mm, but not sure. In any case, it is the size used for most manufacturers of panel switches. The drill is sized to conduit sizes including 1/2, 3/4, and 1 inch pipe sizes. I know Irwin makes one, and pretty sure some others do as well. That 1-7/32 drill has made it a "go-to" for me since the late '80s.

It is, or was, a bit more expensive because of the odd size. But not that much more, I have several scattered around. A big advantage is that they can be resharpened easily by dressing the cutting edge. Following your link, I am somewhat set back at the current price. The last couple I have came from Home Depot:
www.homedepot.com

Klein Tools 1.375 in. High Speed Steel Double Flute Step Drill Bit KTSB15

These Double-Fluted Step Drill Bits provide faster cutting and drilling than single flute bits. The easy-to-read step markings and targets save time when drilling holes. Thick 3/8-Inch hex shank provides
www.homedepot.com
But were cheaper back in the day. Typical I suppose. . .

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Those thing are great. I find the a lot of people run them too fast on the larger steps. As long as you watch the speed, it should last a long time.. When dull, I use a Dremel and carefully dress the face of the flute..

Richard
 
macardoso said:
I've been doing electrical panels for years and have tried all kinds of different tools (hole saws, step drill sets, greenlee punches, trepanning cutters, jig saw, etc.) to make cutouts for electrical connectors and trade size fittings. I've found them all to suck other than step drills, but I found them to be very expensive and limited in range.

I just picked up a new step drill from AutomationDirect for $55. Pricy, but it drills its own pilot hole and goes up to 1.375" (1" trade size) with major steps at 7/8" (1/2" trade size), 1.125 (3/4" trade size), 1.218, and 1.25. It also has minor steps at 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", and 11/16". Split point, HSS, and helical ground flutes. I think this will be the last knockout tool I buy for a long time.

View attachment 406162

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I used step drills a bunch in the telecom work I did but I've never seen two-flute spiral ones before. Very nice!
 
They work well in polypropylene enclosures too.
 
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