SDS Drill bit blunting

[trevorbayliss]

I have got to go through some very hard brick to fit some cavity ties. I am using the mechanical fix ties.

The 5.5mm size bit i have been sent is to small and i have spoken to the company and they say i will need to go up to 6mm size.

So i bought one today while on the job and it lasted for 6 holes and then went blunt. It was a heller drill bit.

So i am now at home looking on eBay for a strong 6mm drill bit which is 350mm in size. There are a few, but i thought i would ask what is the best bit to go with ?

 

[Burnerman]

I tend to favour Bosch or Hilti, but maybe your machine is spinning a bit fast and the drill bit is overheating?
John

 

[trevorbayliss]

Its a basic SDS from screw fix.

Would dipping the tip in water every hole help ?

I will check if i have a speed setting on the drill

 

[Burnerman]

My own machine is a corded Hilti with a maximum rpm of 700 - and nothing stops it.
If you are struggling, consider hiring a drill complete with bits......it could be more satisfactory in the long run. Limited rpm will keep the drill cooler.
John

 

[Deleted member 174758]

Would dipping the tip in water every hole help ?

Waste of time - if the tip is very hot you might even crack it or cause the tip to fall off.

I will check if i have a speed setting on the drill

Doubtful - SDS drills generally run at 650 to 1100 rpm, fixed speed

SDS drill bits are never really sharp - in fact they work by being hammered against the material then rotating. This tends to take the edge off anything, but even when they appear to be "blunt" they are often still viable bits. Personally never had any problems with Heller bits, especially the TriJet ones - they are a darned sight better than the likes of Silverline or Toolpak (for a start, they are at least straight!). What I wouldn't attempt to do is drill a hole with a 350mm liong 6mm bit - instead I'd start with a 210mm long drill bit (150mm depth) to drill the initial hole and then use the longer bits because putting too much pressure behind a long, whippy bit will just bend it, regardless of maker

 

[sparkymarka]

As above they don’t really go blunt ...on hard bricks the end will go flat or loose the tip...

 

[trevorbayliss]

yes this is what happened and then it wouldn't drill into the brick very well. Took along time