Wet Drill Core Bits for Hard Concrete, Granite, Brick, and Block - 3" Diameter 1-1/4"-7 Threaded #30/40 Diamond Grits

The matrix is not as it is pictured. The cost to ship it. I ordered a 2-1/2" and automatically got billed for a 3". the price is good for what it is but the shipping undoes that. Hopefully it doesn't fall apart. Not happy with the shipping cost overall.

There isn't a better bit for the money. We use them abuse them and get more. Depending on how much steel we hit they are good for 50-60 holes. keep em coming.

I needed to drill a hole through a 8" thick 45 year old concrete wall to run the lines for my new heat pump. I picked up this bit, a 1-1/4"-7 Male to 5/8"-11 Female adapter, and a Makita 9566CV variable speed angle grinder. I created a plywood jib to hold the bit in place had an assistant run the garden hose while I set it against the wall and turned it loose. Eight inches of concrete stretched my little angle grinders abilities. As the grinder motor heated up we took a couple "lets go work on something else" breaks. As the bit gets deeper into the wall, it gets harder to keep the bit perfectly aligned and so extra "drag" starts making the amount of work to be done much higher. When I figured that out, I busted out the core slug which made a large difference, and was able to finish up the drill without any further overheating of the grinder.

Drilled several holes about 6” deep with no issues.

I've drilled three 3" holes in 8" concrete walls and the bit continues to perform well. I'm using a hand held drill with a 1/2" chuck to hold the 1-1/4"-7 to 1/2" adapter. Starting the core is tricky and keeping it perpendicular to the surface is tricky. Having a second set of hands makes the start and drilling go much easier. The secret is to use enough water (to wash the cut concrete out of the core), be patient (like any diamond drill) and, as others have said, let the bit do the work. Great value, since having a concrete cutting company come out and drill these 3 holes would have cost me over $600!