Core Drills.

[Matthew]

Hi All,

Im looking for some recommendations for core drills.

I need to drill two holes through brick walls in order to install two 4" extractor fans. I have a bosch sds plus drill but havent used core drills with it before.

I guess there are two types diamond and tungsten teeth. Not sure what make or what accessories are needed. Its only the two holes so I dont want to spend too much. Any advice?

Thanks, Matthew

[stevelup]

Hi

For such a big size of hole you should really use a drill with a clutch - otherwise you risk breaking an arm if the cutter snags. As you only need to cut two holes, I would suggest that you would be better off hiring the equipment.

Our local independent hire firm charges about =A330 for the drill and =A33 for cutters up to 2" and =A35 for cutters over 2"

Steve

[Jim Alexander]

A consumer SDS drill is a bit of a compromise for a 4" hole. Bit too fast for a 4" diamond core and not enough hammer for a tungsten core. I virtually guarantee the tungsten will do little more than scribe a circle.

For a true one-off stitching a circle with a 10mm or 12mm SDS drill is as good a way as any. If a clean cut is really important a 4" diamond core will just about work with a good SDS drill if you can lean into it enough to make the teeth just bite unless the brick is really hard. Hire if you trust the hire shop not to charge you for wear.

Jim A

[John Rumm]

The drill will have a clutch which is vital for jobs like this, what it may lack (depending on model) is power. I have done 4" cores with my

780W drill and it just about manages - you have to take it easy or the clutch will let go.

Diamond core bit and a SDS arbour, and a pilot drill for the arbour. Stick a 8mm hole through the wall first with an ordinary drill, then follow with the core bit. The pilot drill will centre it in the pre drilled hole (this save trying to drill using the pilot and no hammer action!).

If you are doing both holes on the same day then hiring might be more cost effective. Having said that if you buy it, you will probably find other uses (and users) come out of the woodwork! So it may keep you in beer tokens.

[John Stumbles]

I have used SDS drills for coring up to 110mm and it's a PITA. The only SDS machine I had which did have a clutch had it set too low (and it wasn't adjustable) so the core would get stuck in the hole with the machine uselessly clacking away on. Funnily enough it was worse with small cores: the 100mm wasn't too bad. On clutch-less machines you're forever fighting the kick when it snags. A lower-powered machine is easier to handle in this respect! None of the SDS-es had variable speed control.

I now have a relatively cheap 'proper' core-drilling machine which is a pleasure (relatively!) to use. Its variable speed control is particularly good when starting a hole. The mechanical gearbox gives good low-speed torque and it has an effective safety clutch. It took me a while to accept paying over £100 for a single-use machine but it's worth it for the ease and safety of core-drilling, which I do enough of in my work to make it worthwhile for me. The machine is also good for drilling large holes in metal (due to its keyed chuck which grips twist drills firmly) and for mixing plaster etc with a paddle.

[John Rumm]

I had to smile the other day, walking back to the car in a multi-story car park there were a couple of bods from a specialist diamond drilling firm, sticking what looked like a deep 2" core into a re-enforced masonry wall - about 2" off the ground. Your main drill man was knelt with one knee either side of the drill, and the side handle just poised to take a side swipe at his gonads on the first snag....

I did not stay to watch!

[John Stumbles]

Oh yes, I did say to keep all delicate body parts out of the way of the machine, didn't I? I once got whacked on the cheek (dangerously close to the eye) by an SDS that snagged. It was only driving a 12mm drill in brick, too, so I didn't expect it.