Hammer drill size vs. drill bit life

[FastKat]

I need to install two round 5" electrical boxes in a brick wall for outdoor lights. I have access to both sides of the wall. My plan is to draw a circle, drill holes around the perimeter, and tap away the bricks with a hammer and chisel. I can augment this with a 4" diamond wheel on an angle grinder, which works great, but is limited to shallow cuts.

I have a cordless DeWalt 20v impact driver that I previously used to drill 1/4" holes (1/4" Bosch masonry hammer bit from Lowes) but I did not get the life out of the bit that I expected. In this application I can have almost any size hole. Would I get more holes out of a larger bit? If yes, what size would you use?

 

[Jeff Ivers]

Do you have a hammer drill you can use instead of the impact driver?

 

[FastKat]

Now that you mention it, my dad recently bought one. Maybe I will wait and use that.

 

[toplessHO]

bosch,Hilti,Milwaukee all make good masonry bits.
But once youve overheated them they are toast(lol)

 

[rancherbill]

Go to Rental store and get an SDS style drill and the correct size hole bit. It will cut it in minutes.

 

[strutaeng]

An impact gun to drill holes in masonry? I'd never thought of doing that. Is this a single wythe of brick?

Use the right tool. An SDS+ Bosch Bulldog with appropriate bit, probably 1/2" diameter.

The better tool would be a concrete/masonry core saw bit. I think home Depot and Lowes carry them. They look kinda like a regular hole saw and can be used dry. But they are expensive.

A real core saw with water would be even better, but rental is a few hundreds of bucks.

 

[rpenner54]

Done it that way. The core bit rental works well as well but yeah I just used a 1/2" bit and made a circle for the last dryer vent I needed to run through some brick. Brick is soft so you don't have to use a hammer drill but it does help. Go slow since brick is soft as its easy to break off a chunk you don't want too. The mortar is hard though.

 

[American Locomotive]

FWIW: I don't think impact drivers would be very effective with a masonry bit. Hammer drills and SDS Rotary Hammers work by hitting the drill bit forward. So they actually chip away and break some of the masonry. The flutes on the drill then carry the dust out.

 

[dutchgray]

Using an impact driver with a masonry bit will just kill the bit from heat generated from friction.
Get an SDS drill, they are not expensive and they work so well.

 

[hefnerconstructionlc]

Score with grinder diamond blade. Use bit for thru cut. Keep spray bottle handy with water. Will be done in no time. Chip out with hammer.

 

[Certified Drunk]

Use the proper tool for the job, Dewalt hammer drill is joke.

 

[FastKat]

Thanks guys. I did not realize a hammer drill hammered out into the material. I thought the hammering was in a twisting motion like an impact driver. I bought an open box DeWalt impact driver on eBay for small holes and will probably rent a core saw from HD for the two large electrical box holes. The core saw are great... I will spend more time driving the tool back and forth to HD than I will making the actual cuts!

 

[fitter30]

Brick is soft compared to concrete. Hammer drill will go right through it.