On Wed, 10 Oct 2007 05:52:39 -0700, Matthew wrote:

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?

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.

http://www.screwfix.com/app/sfd/cat/pro.jsp?id=70952

--
John Stumbles

Bob the builder / it'll cost 'yer
Bob the builder / loadsa dosh