4-1/4" Dry Diamond Core Drill Bits for Brick and Block with 1/2" Shank Pilot Bit Adapter, 9.5" Drilling Depth, 5/8"-11 Arbor

I ordered this to drill through an 8" concrete wall. I was not expecting much out of this core bit, considering the price, but I only needed it for one hole. This bit went right through the wall with no problem, very quick and no binding up.

I had to core drill seven holes in brick wall for electrical boxes, wife went overboard with her backyard light design but it is what it is. The brick veneer is about 4” thick, very hard stuff. I’ve got 4 1/4” core drill bit, the main reason it was on sale and much cheaper than 4” diameter one. Here is what I found.1. You absolutely have to drill the guide hole first separately, the included center bit will not do anything unless you remove it, drill the guide hole in hummer mode, then reinstall it back for core drilling which is rotary mode only.2. You really don’t want to use cordless drills, whatever strong it may be, even my 7A corded one barely had enough power for 4 1/4”. It started smoking at the end, so I’ve pulled 13A Milwaukee SuperHog which was perfect for the task on low mode.3. The bit lasted me through 7 brick holes, but the 7th one was much slower, I’d say the 8th one will be the end of its life.4. The included M8 nut to hold the center guide drill bit is garbage, the hex wrench doesn’t have enough torque to make it tight and is awkward to use. I’ve lost it on my 3rd hole and switched to M8 bolt which was much better.All and all the bit did what it is supposed to do, for the money I’ve got everything I wanted. Except the hex nut design I have no complaints.

Worked great on brick wall. Nice clean cut, no chipping of the brick. Even used on my battery drill NOT in hammer mode, in low. Took about 5 minutes to get all the way through, shorter than I expected! The bit is advertised as a dry bit but I used a spray bottle to keep it wet.Knocked off one star because there is an arbor in the photo and my bit didn't come with an arbor. Luckily had one, but wasn't able to use pilot bit because the arbor I have doesn't have the hole for pilot bit. Not a problem starting it slow at a slight angle.

Worked great for cutting out 4inch hole, but should've gone up one size larger to make it easier to fit 4inch pipe. Also will need a strong hammer drill to turn this without burning out.

Yes, the core drill held up and drilled several holes in concrete blocks.

This core bit really works as advertised and beyond. I had to core out an external wall for a mini-split install. The wall is drywall, insulation and 8” of cinder block; not all the cells in these type of walls are concrete filled, but I won the jackpot and hit concrete and a 5/8” rebar. The concrete was easy, the rebar took a little longer, but it got thru. No hammer impact, just slow drilling with light pressure on the drill.The only downside is the guide bit; the set screw comes out due to the vibration, no matter how tight it is. My suggestion is to drill the pilot hole just with the guide bit, then use the bit and core to score the hole. Once it gets going, you can do without the guide bit.

I paid for a new core drill bit and I received a used dull one!

Like many other commentors I was adding an bathroom exhaust to the outside. A long deep coring tool looked really promising and at this price point I took the plunge. Initially I purchased the Bosch coring bit but that sucker was expensive for just a 4' deep hole saw. And to top it all off they didn't have a Bosch bit adapter in stock. So I put it on order for the next day or so. When I saw this on Amazon I was thinking hey this is a great cost effective solution I can return the Bosch. The bit started out great by cutimgt through the brick like butter however cutting through the wood was a major exhaustive battle for me. The night fell. I even tried to finsh the cut with my 4' wood hole saw and that is when I discovered that this hole saw is not really coring a standard 4' hole. As a result I could not get my wood saw past the brick. Finally on the next day picked up the Bosch adapter and decided to sacrifice the Bosch to finish the job. I was able to open up the hole to a proper 4 3/8 which allows proper fitment. Because I used that the deep coring bit first it made finishing with the Bosch a breeze. But I paid a high price in the end. I am not certain I would have been any better off if I had just started out with the Bosch because it was much to shallow too core through about 9 inches of material