drilling in concrete with hammer drill

[ballard770]

I just finished stairs for my low deck with the help of Buzz, my handyman and I am installing a handrail for my wife. The upper part of the rail is a slam dunk as it fits against the tall post of the deck. The bottom fits on a 4”X4” post base fastened into concrete and I broke the carbide tip of my masonry bit that is used in a Porter cable hammer drill.

The base requires four bolts with anchors. The first hole went slow and I stopped at about 3”. On the second hole it went slow and then the carbide on the bit broke. I am wondering it I struck rebar or a steel mesh but I doubt that the builder would have had the masonry contractor put any steel in the 80’ plus rv driveway.

i am thinking either steel or perhaps the bit was at the end of its lifespan. I’ve probably drilled 20-30 1/2” holes in concrete about. 3”-5” deep. I am going out to get another bit in the morning and I wii give it another try. The bits are a little spendy but it works out to 50 cents per hole which is not too bad. The bit is one that is suitable for hammer drills.

i had thought about flushing the hole with water periodically during the drilling but I don’t like using electric drills in a wet environment - perhaps it would cool the drill bit and prevent the carbide from breaking.

any advice will be appreciated.

Lee

[leehljp]

I don't know what the lifespan of a carbide drill bit should be but to me you got more than I usually do. I also have learned to buy the better ones - i.e. the BETTER name brand ones as they seem to do better for me. I don't need them but about every two to three years. I needed to drill some 3/16" holes very carefully in bricks a couple of weeks ago. I used a cheap carbide on and it dulled quickly, bought a twice as expensive one and it drilled a dozen holes or so and it is still good.

[woodturner]

A 1/2" hole is large to be drilling with a hammer drill, it will be slow going. A rotary hammer such as a Bosch Bulldog with an SDS bit will work much better. The problem with a hammer drill is that the bit slips when the hammer impacts, so much of the impact is wasted.

Are the drill bits you are using rated for impact? Many smooth shank masonry bits are not, they are intended for drilling not impact drilling. If you are using a non-impact bit in a hammer drill set to hammer, it will not last long.

[capncarl]

I’ve had some real horror stories installing handrails on the sides of concrete steps with the anchor holes causing the step to crack or a chunk break off. I had a Bosch hammer drill with a SDS chuck that I liked, it didn’t have as agressive hammer action to it, rather almost a buzzing vibration. It went through concrete like butter and had less blow out than some of the larger hammer drills. You could drill 100s of anchor holes with a single bit until you hit rebar and ruined the bit. My favorite way to anchor handrails was to use 2 part epoxy anchor material and stainless threaded rod. It won’t pull out or loosen up, and it won’t rust off.

[Slik Geek]

I used a rotary hammer for the first time late last year to drill a bunch of 3/8" diameter holes in concrete. It was so quick and easy it was fun. Best purchase ever. I NEVER use my hammer drill any more for drilling concrete or stone. The difference is stunning.

[os1kne]

I agree - for drilling holes in concrete, the difference between a rotary hammer and a hammer drill is stunning. When I started on finishing my basement, I used a hammer drill for drilling ~ 10 holes into concrete. It was painfully slow going - bits weren't lasting more than a few holes. I knew that I'd need to do at least 100+ more holes, so I bit the bullet and got a Bosch Bulldog rotary hammer (most basic model ~ $160) and a proper bit. It easily drills into the concrete. I've drilled 100+ holes and it's probably time to replace the bit.

[jabe]

i cool the bit in a cup of water after drilling a 3rd of the depth I need to drill, I just dip it in the water for a few seconds and proceed to drill again. I use that method regardless of just drilling or hammer drill in concrete seems to save my bits. Buy the best drill/bit you can afford, you get what you pay for.