I need to drill a large number of holes in my poured concrete garage walls to put up some adjustable metal shelf "standards" (rails). The rails are a u-chennel with slots for the actual shelf brackets, and have 5 countersunk holes spaced along them. I made a drill guide that ensures that once the ends are in place, the holes for the screw anchors will be located accurately. I have a 1/2" Bosch hammer drill to drill the holes, with the appropriate carbide tip drills.This all works OK, but on a couple of the rails, the ends drilled OK, but I'm hitting aggragate or something very hard on the inboard holes. It takes forever (~5 minutes of steady drilling for 1/16" of progress) to make a hole. My hands are getting numb from the constant pounding. Somewhere I have some anti-vibration gloves for my old lawnmower, and I really need to find them.What I'm wondeirng is what's the most efficient way to use a hammer drill. Is it best to let it chip away slowly at things & just be patient, or will really leaning on it help? There are a couple of "operating points" for the thing. Too little pressure, and it doesn't hammer at all. A little more pressure, and it start buzzing, but it isn't recoiling too badly. I could drill comfortably at that level for a long time. If you lean on it a bit harder when it's hit something hard, every time it hammers, it hammers on my hand as much (if not more) than on the hole. Aside from the pounding on my hands, I don't know if leaning on the thing is going to destroy my drills prematurely. When I'm drilling the top end holes without a guide, I know that if I use too much pressure the drill tends to wander more, but with the guide, that's not an issue.I've got 4 tough holes in partial levels of depth, and another 5 to start. The good news is that I've got 8 holes finished. Any suggestions would be really appreciated.Thanks!Doug White

Hi- You may have hit some reinforcing rod. You should not have to push hard. Less force than trying to drill a 1/4 inch hole in steel. If you can beg , buy or borrow a Hiltehammer drill, the type with the axial hammer , and not rotary impact, your troubles will be over. It will drill a 1/2 inch hole in four inches in concrete in 15 sec or so. Jim

Hammer-Drill Technique?

Nov 27, 2005 23 Replies

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Pete C. 20 years ago

I have the relatively inexpensive Hilti TM7S-VSR hammer drill and even though it is a hammer drill and not a rotary hammer it does a really good job even with 2" core bits.

Last I knew the Hilti rotary hammers took regular SDS bits like everyone else.

Pete C.

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Scott Moore 20 years ago

Doug White wrote On 11/26/05 19:03,:

I was doing the same job the other day. Sometimes the holes got real slow, so I changed to a smaller drill, and drilled a pilot hole first, then the big drill had no problem.

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daniel peterman 20 years ago

I think I actually used a drill as a hammer a few times. I believe it was Thor brand

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DanG 20 years ago

Was this the old Thor with the huge rubber band hammering mechanism? Actually quite effective for its vintage. I don't know what one would do if you wore out the rubber band.

(top posted for your convenience) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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