Drilling insanely hard stone

[TomEC]

Afternoon chaps,

I'm having a litte problem that I'm hoping someone may be able to advise on.

I am building a shed in my back garden (it's actually going to be a very small pub, but more about that in a later post). When I moved in there was already a reasonably flat patio down over most of the area that I want to build on, so I just filled around the rest of the area with concrete and now I plan to start building by fixing a timber deck down to the patio.

The problem that I'm having is that the patio stones seem to be made out of adamantium or something! I swear there can be no harder substance known to man! I need to drill some holes in them to screw the timbers down to, and so far I've managed 3 holes and melted 2 drill bits.

Does anyone have any advice how to go about drilling into very hard stone? I'm only using regular masonry bits (the brand was JCB) and a Bosch electric hand drill. Is it worth me hiring a larger drill? or are there some special drill bits I could try?

Thanks in advance.

Tom

 

[Gerrydelasel]

Tungsted carbide tipped (TCT).

 

[Lower]

Are you using a hammer action drill?

 

[TomEC]

@ Lower - yes, using the hammer setting on the drill

 

[Burnerman]

Head to a tool hire shop and explain your problem.....you'll come away with a quality 250v -or 110v - SDS drill, slow revving with a powerful (probably pneumatic) hammer action and bits to suit.
John

 

[Brigade77]

If this "small pub" were local to me, I'd pop round, drill & probably find oil for you

 

[r896neo]

An sds is much more suitable for the job. Problem is it may crack the slabs.

 

[SFK]

Tom,
My apologies if you are already trying this and if this stone is too hard for my suggestion.
First, the SDS drill and the hire drill will work better than your normal drill.
But, how did you try drilling the holes? With masonry drill bits when I find the going very hard, I start with the smallest drill bit in the pack, drill a pilot hole and then work my way up the sizes.
Less stress on the stone and reduces heating on the drill bits as each pass is only widening the hole.
SFK

 

[r896neo]

Be careful and change significant sizes at a time, avoid going up 2mm at a time as that technique will shatter poor quality drill bits as they get jammed especially on hammer action. jump up 5mm at a time or just rent/borrow an sds