I need to drill a 4 inch round hole through a concrete block wall to make room for a 4 inch dryer exhaust vent pipe. The block is approx. 8 inches thick but has hollow cavities in the middle. If this were wood, I would use my 4.25 inch hole saw attached to a corded drill. However, this is concrete block` and I need to know how the pro's do this. Is there any way to do without having to buy expensive drilling tools? I hate buying expensive tools just for 1 job. --68.63.xxx.xxx

The easiest fastest way is with diamond tipped coring bits & a coring machine. Lacking those mark a circle slightly larger that 4" on the block wall, drill a series of small holes on your mark and punch out the derbies with a hammer. You might want to carefully run a pilot hole thru the center of the proposed hole so you can drill from the interior as well. --96.237.xx.xx

--184.53.x.xx

I just did this a month ago with a 12 block wall, of course I needed to have the whole right where a joint was. I used a cheap air powered chisel with the pointed head. New the the air gun is like $40. If you dont have one, borrow one, most handy guys have one or two around. It did a good job. While a diamond hole saw would work better and more precise, it is VERY expensive. --184.102.xxx.xxx

What type of chisel is best to use here? I have chisels for wood but not for concrete. --68.63.xxx.xxx

Youtube --50.107.xxx.xxx

Hammer and chisel. You'll need to go from both sides into the void area. When done get some concrete caulk-- used on chimneys to seal the aluminum tube going through the concrete. --99.103.xxx.xxx

I have seen my plumber use a hand-held 'jack-hammer' type tool. Is this what you are referring to? --68.63.xxx.xxx

You could use a 1/4" masonry in your drill to do the same thing. Then use either a small masonry chisel of one of your wrecking bars to finish things up. Unless the block has been completely filled with grout it shouldn't be too bad to do. --96.237.xx.xx

--24.34.xx.xxx

I rented a hammer drill and carbide hole saw from Home Depot. Did a fast and neat job. Be careful when drilling, the drill has massive torque. If the hole saw "grabs" you will be yanked around unless you are both large and strong. Safety goggles and dust mask are a good idea too. --157.204.x.x

DIY is how you end up with a garage/shed full of tools that get used once a decade. Bleh. ;-) --173.20.xxx.xxx

b) use a roto-hammer or hammer drill with a 1/4" to 1/2" Power Masonry Drill Bit. Drill many holes in a circle spaced slightly apart. Then using a hammer and chisel break the block apart between the holes. A hammer drill costs only around $100 and a masonry bit costs around $10. Or use a roto-hammer costing aroudn $150 and a SDS-Plus plug in masonry bit, around $15. --47.156.xx.xx

--73.152.xx.xxx

Cold chisel is good for just this one job. Lightly score the outside area of the desired opening and work inward from there. --66.226.xx.xx

Rent the tools. Your body will thank you. Get the biggest hammer drill they have. --98.122.x.xx

Wow. That's some hard work. I have seen that kind of work during installation of exhaust fan vents. And yet there are women who don't think there is a real need for guys like you. Re education needed. If women were in charge we would all be living in pile of sticks in the woods. Thank you for your hard work. --73.178.xxx.xx

Roy, you can do it, we can help ! --99.59.x.xxx

I have done this. It's not as bad a job as you think. I do what Steve [MA] recommends, but I just used a regular concrete bit. I drilled a 4+ inch circle of relatively small holes. I think I used maybe a 1/2 inch bit. Then I used the ball end of a ball peen hammer to take out the rest of the block. Then I got to do it again on the other side. But the whole thing only took an hour or so. --68.156.xx.xx

The type of chisel or roto-hammer is one you can wear gloves with, to make the hole back to round slide a short section of 4inch tubing like the leftover from a water heater - but do not close the seam, mortar around this and pull the sleeve 2 days later - it will wiggle out easily with the seam open leaving you a well rounded hole - pun intended... --76.188.xxx.xx

I rented a hammer drill with a 4-1/2" bit from Home Depot for about $90 and it took about 20 minutes to drill the hole through an 8" thick concrete foundation. --38.142.xxx.xxx

Start with a few holes with a masonary bit. Use a hammer and chisel to knock out between the holes and start chipping away. Took me about 40 minutes with a brick wall and concrete blocks behind it. If yours is only concrete block it should take less than 15 minutes. It won't be perfect but your 4 in duct should have an outside cover and flange to hide any imperfections of the hole. --72.49.xx.xxx

--47.216.xx.xxx

You could also use a grinder with a diamond blade to score around the 4" diameter circle from the inside and also the outside and knock it out with hammer and chisel. Use a long masonry bit first to go completely through the block to act as the center of your circles so that they line up exactly. --73.141.xxx.xxx

BRAD --68.50.xxx.xxx

Roy, you already have the drill,so all you need is a 4 @nd a quarter inch diamond core bit.drilling from both sides,they call it diamond tipped,not real diamonds.and then you can finish it off with a regular hammer and a Hslf inch cold chisel.if that doesn't work then you can try LTDs method,just use ear plugs,if you do........charlie............and run like hell...................................... --32.214.xxx.xx

Most of the information is good,but the cost is going to give Roy a heart attack and the ambulance ride and the couple of days in the hospital may not be worth it,if you drill from both sides the first One and a half inches is the worst,the middle of the block is easy,just remember that.................... .charlie..........just like butter......... ......... ... --32.214.xxx.xx