hey guys, building my dream garage and i'm almost done but the city inspector wants me to install eleven HTT22 straps along the baseboard walls. i guess this is another earthquake prevention deal. anyway, i bought a 7/8 masonry drill bit that costs $31.00 and we only got to 3 fricken holes when the bit took a dump. its duller than a worn out eraser. my question is this. whats the proper procedure for drilling a seven inch deep 7/8 hole in concrete thats only a year old? i didn't add water and a couple people are saying that i should of put a little water in the hole to keep the bit from getting too hot = too hard. or, did i simply buy a defective bit? some say that you should drill ten seconds let up for ten seconds,drill ten seconds,let up for ten seconds. i just dont know. any construction/hambers out there?
pour cold water on it all the time when you are drilling,and to be safe,take it up and cool it directly with water,those things get extremly hot.
are you using a roto drill/ hammer? if not... go to Hertz (or who ever is near you) rent a concrete drill w/ bits and save yourself the trouble. a proper drill/ hammer set up should go for ages w/ out dulling.
yeah, You'll never drill that large a hole with a regular drill. Go buy a hammer drill at Home Repot and then return it when you're done. Using water won't hurt either...
a light touch, and a slow speed on the drill helps, let the bit do the work, and do not overheat the bit. also it is not uncomon for a hole that deep to consume a drill bit depending on the aggregate used in the concrete.
Are You Using A Hammer Drill? You Shouldnt Have To Put Alot Of Pressure On It If You Are Let The Bit Do The Work. I Used To Install Balcony Systems In Another Life And Had To Drill A 1 1/6" 8" Deep Hole And It Only Took About 15 Min Or So Per Hole. Dont Use Water It Will Gum Op The Bit If Anything Once In A While Take A Turkey Baster And Blow The Dust Out Of The Hole. Put A Little Pressure On The Hammer Drill For A Minute Or Two Then Pull It Out And Do It Again, All Whal Drill Is Running. This Will Help Keep The Hole Clean. If Dust Builds In The Hole It Will Effect The Drill More Than Anything Dust Is Harder Than Cement When Compacted.use A Hammer Drill And Keep The Hole Clean
Cooling is key, water, water, water and a Hammerdrill of course. The Garage Journal has tips for this kind of stuff
I don't know how many holes you have to do, but you should be drilling with a hammer drill that uses SDS bits. I happen to own one, but you can rent them (they are expensive, my Bosch cost $250.00 six years ago) You'll have to buy the bit, I doubt they rent them. They drill through concrete like it's wood. You'll have less than a minute per hole, no water necessary. The fly in the ointment (seems like there always is one) is if you hit rebar in the concrete. This may be what happened to you. I hope you have the option to move the hole if that happens, I've never found a way to drill through rebar without trashing the bit. As soon as I feel the bit slow down, I check for steel. Blow the dust out of the hole, and if you don't see steel, check with one of those telescoping magnets to see if it's steel or just some extra hard aggregate.
Use an adequate size roto-hammer (that can handle that size bit) with either an SDS shank bit or if a larger tool, a splined shank bit. I would suggest a rental yard for this since it sounds like a one time thing. A little water will help keep things cool and be sure to hold on with both hands in case it locks up on you. If you are near So Cal I can loan you the tool. Good luck.
I'd rent a Millwaukee hammer drill or borrow one from a friend. They are designed just for that type of work.
Cement rock chisel the end is shaped like a + .You drill until the bit will not drill anymore and hammer the chisel in the hole and it breaks the rocks so you can drill deeper i had to use one in my shop also worked great.
being in the maintenance business i've done my fair share of concrete/masonry drilling and a hammer drill and water is the way to go. one thing that wasn't really mentioned is to make sure you back the bit all the way out every so often (i usually do about every 5-10 seconds depending on hole size or when it starts steaming) to clear the dust/slurry created with the drilling and water. spray the water on the bit and into the hole liberally. the other thing is get good titanium oxide coated bits, the best ones i've used are vermont american...they are a bit pricier but i've seen better life out of them than the others i've tried.
When using a roto-hammer, don't press down as hard as you can. It will slow you down. Let the tool do the work. Firm, steady pressure is the way to go. A roto-hammer and a new bit will do your drilling, no water needed. I'm a jourmeyman electrician with better than 26 years in the trade. Believe me, I've drilled my share of concrete.
man, i'm speechless. thanks a million guys. i guess i f#@%! up. i went in the garage and grabbed a good size regular makita drill and we just put that sucker at high speed and went for it. i figured as long as i used a masonry bit it was all good. this roto / hammer drill you all are talkin about and a little water sounds like the trick....cool ! thanks thank thanks! axle
that's the good thing about hammer drills, most have a switch on the top so you can either use it to drill stucco, concrete......or flip the switch and use it as a regular drill.
He's right, no water & medium pressure, you'll see what pressure it takes when it starts eating. Just keep pulling it up to auger out the powder/dust and go right back down. The drill has a ratcheting mechanism in it that shoots the chuck in and out at a high rate so it chisels as it drills, that's why the bit tips look like a chisel. It'll drill so fast you won't believe it. I've never worn out a bit yet & I know my 1/2" bit has drilled at least 200 holes.
I used to drill holes with a hammer drill and a 'crete bit when installing signs onto concrete. Not too much pressure - about medium. It's all about the drill - and drill speed. To much pressure or speed and you'll toast a bit in not time flat. Keep the hole cleaned out - blown with air or water. We never had access to water so we just gave 'er the old puff puff from the mouth (close yer eyes first! LOL) Nothing that hasn't been suggested already I guess. I think you'l get 'er now....after another $30 bit of course!!
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