Discuss Best Masonry Drill Bits for Combi Drill in the Electrical Tools and Products area at ElectriciansForums.net

Electric Magic

Electrician's Arms
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266
Location
Manchester
At the moment I tend to use these Erbauer ones, they are very cheap and initially quite good but (unsurprisingly for the price) don't last very long. What do you lot use? Are there any that are 2 or 3 times the price that last more than 2 or 3 times as long, or should I just stick with the cheapo ones?
 

buzzlightyear

please let me back in to the prison cell.
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star command
a good quality one will last longer then a cheap Chinese one ,what I'm on about ,they are from china .
 

buzzlightyear

please let me back in to the prison cell.
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6,887
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star command
mines brown right through the bottoms and out side the other side .
need a crane to just to yank them out of them .;)
 

Vortigern

Regular EF Member
Messages
4,766
Location
England
I have had very good results from bosch masonry drills. You can also drill through wood. Been using them for 4-5 years and they still work as good. They cut into brick and block work really fast. Mind you if I am up against something that is hard to get through I do dip the bit in water to cool it off and that may have something to do with the longevity. But for speed so far they are unsurpassed. It is important when I work in commercial offices to keep down the noise especially the duration. These will drill brown/red plug holes 6mm/7mm in about 5 seconds. I time it so that I can drill for fixings for say a DB faster than they can get on the phone and complain and get the reception to get me to stop work!;)
 

billyblade

Active EF Member
Messages
33
Location
Sheffield
A lot of the time, it's not the bit that's the problem, it's the machine. Straight shank masonry bits are obviously used in machines with 3-jaw chucks. To the majority of users that means a combi drill. The impact energy of combi drills is vastly inferior to SDS machines.
On a combi drill, it's a percussion function where the chuck moves backwards and forwards on a cam.
With an SDS machine there is actually a piston that is fired forward onto the end of the drill repeatedly to provide the hammer action. that is why you shouldn't lean on an SDS machine because you are actually suppressing that piston.
With heavier duty masonry (engineering brick etc.) only the higher impact energy of an SDS machine will do. Using a straight shank in a combi with the lower energy percussion function causes a lack of progress, this leads to a huge heat build up. On cheaper drill bits this can actually melt the braze that fastens the tungsten carbide tip into the end of the drill or even disintegration of the tip itself.
The more professional drill bits have a better grade of carbide tip and a higher melting point braze but in some masonry even they won't do.
SDS masonry bits (when drilling in hard materials) should be considered as rotating chisels rather than cutting bits. It chisels, turns slightly, chisels again, turns slightly and so on until a hole is formed. With a straight shank in a combi there is not enough impact energy generated to do the chiselling efficiently.
 

Rpa07

4000 posts - only 54195 behind Telectrix!
Electrician's Arms
Messages
4,204
Location
Bristol
A lot of the time, it's not the bit that's the problem, it's the machine. Straight shank masonry bits are obviously used in machines with 3-jaw chucks. To the majority of users that means a combi drill. The impact energy of combi drills is vastly inferior to SDS machines.
On a combi drill, it's a percussion function where the chuck moves backwards and forwards on a cam.
With an SDS machine there is actually a piston that is fired forward onto the end of the drill repeatedly to provide the hammer action. that is why you shouldn't lean on an SDS machine because you are actually suppressing that piston.
With heavier duty masonry (engineering brick etc.) only the higher impact energy of an SDS machine will do. Using a straight shank in a combi with the lower energy percussion function causes a lack of progress, this leads to a huge heat build up. On cheaper drill bits this can actually melt the braze that fastens the tungsten carbide tip into the end of the drill or even disintegration of the tip itself.
The more professional drill bits have a better grade of carbide tip and a higher melting point braze but in some masonry even they won't do.
SDS masonry bits (when drilling in hard materials) should be considered as rotating chisels rather than cutting bits. It chisels, turns slightly, chisels again, turns slightly and so on until a hole is formed. With a straight shank in a combi there is not enough impact energy generated to do the chiselling efficiently.
I had that exact conversation in my head yesterday whilst driving. You’ve confirmed everything my wandering brain told me. Cheers Billy
 

Bellendian

Regular EF Member
Messages
199
Location
Gatwick
Bottom line...ditch the combi and get a battery SDS and impact driver. Only use the combi for holesaws really these days.
 

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