UKC

I have a collection of ~50 rock offcuts from a stonemason (mostly gneiss, but a few are limestone or sandstone). I am trying to drill screw holds in them so I can use them as handholds on my board.

I have a fairly powerful hand drill (Makita HR2470), some 6mm diamond drill bits, and a diamond countersink bit.

But even with these, drilling the 3 screw holes for one handhold took around an hour.

So far, I haven't been using the hammer (combi) function on the drill. I tried using it briefly on one of the sandstone holds, and one of the limestone holds. It sped things up quite a lot, but it shattered the holds before the hole was complete. I haven't tested the hammer mode on a gneiss hold yet.

​​​​​​Does anyone have any tips or advice that may speed the process up? Or is it just the case that drilling through rock is a very slow process?

Might the hammer mode be worth trying again but trying to be very cautious with how much pressure I put on the drill? And if so, an I better off aiming for a faster speed or slower speed?

Buy an SDS hammer drill. Will be much better. Never drilled neiss, but sandstone and limestone should be very easy. 
 

you can get a cheap mains sds if price is an issue. Or get a Makita one so you can reuse the batteries and charger etc

How big are the holds? Exactly what drill bits are you using? Is it the through hole or the countersink that's slow? I've drilled a few rock holds and I don't think they took more than 5-10 mins per hole, though I didn't bother countersinking. Your drill looks a lot more chunky than what I was using.

Just guessing, but might be worth slowing your drill speed down a little and adding some water to cool things down and clear material from the hole and bit. Diamond bits essentially grind through the material so might be getting clogged, especially with the softer limestone and sandstone.

I'd be a little wary using an sds hammer drill on the sandstone and limestone, I'd have thought you'd be likely to crack them, or just munching your tiny 6mm drill bit. Would be easy enough to experiment though, just pick some of the shitter holds and give it a go.

I’ve found that drilling limestone holds with a SDS drill in hammer mode will shatter the hold. Diamond bit with lots of water is the best way (put in a small container so the hold is submerged, or try to run water across the hole to remove dust) but unfortunately takes a long time 

I once inherited a wall where the holds were all drilled rocks. The original owner and driller used it as a hobby, bring a rock back from holiday, drill it and place on wall.

Drilling them is hard work, the sort of job given to prisoners in a sunny day, expect a high breakage rate. Holds will break and spin in use, adding another dimension to training.

Use wise, rounded pebbles are best for a steep wall, sharp, scree like holds aren't great on your skin.

There are many reasons why drilled rocks aren't available commercially. Drilling your own, whilst a nice project just isn't cost/labour effective.

Crikey, drill your own hole. I remember that LP, and having to drill my own hole in its centre.

The Gneiss is going to be hard, the others should be pretty easy if you can avoid splitting them.

First of all make sure they're flat on the back so they sit still for drilling and on the wall, you could grind them but it'll be less dusty to add some car body filler and press them down flat onto parcel tape which acts as a release film then wipe away the excess at the edges.

A diamond coated spade bit (sold for tiles) will work, use it submerged in a tub of water and go reasonably slow with a steady pressure to keep things cool and cutting. A drill press helps. With softer rocks like slate you can even get away with HSS twist drills using this method, just don't expect them to be any good when you're done unless you can re-sharpen them. You'll want a diamond or carbide burr for countersinking anything harder than slate.

For the gneiss you're likely to need some hammer action and a carbide tipped masonry drill, start slow then ramp up the speed and pressure as the hole starts. Again, doing it wet will help the drill last and to control the dust. Having the flat back to the hold and a solid slab under the hold you're drilling will help the hammer action.

If I was doing loads of them I'd have a go making a thin walled tube cutter in brass or copper to hold diamond paste, use that on a drill press.

Basically it's a pain in the ass, you might be better just gluing them on with a decent builder's adhesive.

jk

Cant say i know of a product but some kind of resin might be a simpler option?

The holds are a mixture of smallish crimps, rails, and pinches. Ranging from 1/4 pad thick up to just over a pad thick. They have a perfectly flat back for mounting on the board from when they were split by the stonemason.

I think ukc blocks links to eBay, but if you search for "6mm diamond core drill bit" there are lots of results that are the same as what I have. The tip is a cylinder which is coated in diamond on all surfaces. Further up the shaft, there is a small amount of gel which claims to assist with lubrication and cooling. I have been doing all of the drilling dry, I haven't tried any water cooling so far.

My process so far has been:

1) Drill a small starter hole with a 6mm carbide masonry tip. This is just to stop the diamond bit from wandering. This stage doesn't take long. 

2) Switch to the 6mm diamond drill bit to drill the rest of the hole. This is the slow process. I pause drilling every ~30 seconds to blow away the rock dust from the hole and the drill bit to try and stop it clogging. The drill bit and the rock get quite hot. 

3) Switch to diamond countersink bit so I can add a washer. This doesn't take long.

I will experiment with water cooling next as everyone seems to be in agreement that this is the way to go.

I have been starting the hole with the drill on slow, then ramping up to full speed as soon as the hole is deep enough to prevent wandering. Full speed on normal mode seems to be a lot slower than full speed on hammer mode.

I will give it a trial with one of the gneiss holds. I have 3 of the diamond 6mm bits, I expect I will need at least that many to drill all of the holds. I think I've already concluded that hammer isn't the way to go for limestone or sandstone.

Resin looks great and is probably the easier option like this: 

https://www.frictionfactory.co.uk/gallery/

Sadly, my board is already very densely packed with holds, so I can't afford the extra space that a resin back takes up. 

I've already had to implement a "one in, one out" policy for new holds after finally accepting that there is no space for any extra holds.

Did you use one of the cylindrical diamond core bits like mine or a diamond coated spade bit?

The holds all have a perfectly flat back as they are offcuts that were split from larger rocks.

A drill press would be ideal. Sadly, I haven't been able to source one.

Yes the same sort of cylindrical diamond coated bit you mention

I suspected they might become a bit of a hobby task before I started, but it's safe to say that it's been tougher than I expected!

The holds may break, but I won't have any issues with spinning holds because they will all have multiple screws in them. 

Working the skin is actually the reason that I want them on my board do I have deliberately selected hooks that will work the skin a bit.

I have very thin, soft skin and it gets even worse when I haven't climbed on outdoor holds in a while. I'm hoping that these will allow me toughen the skin up a bit from home when I'm not able to get outdoors.

Quick update: 

I experimented with water cooling this evening by submerging the hold in some tupperware.

It doesn't make a noticeable difference to the time it takes (I still took ~1hr to drill the 3 holes for a single 1 pad flatty/pinch), but it was a lot easier to do:

No dust or mess, no need to wear a facemask, the bits/rock never get particularly hot, you can drill for longer before stopping each time because it doesn't clog (I stopped every couple of minutes to change the water once it had gone very cloudy), and I didn't need to put so much pressure on the drill so the bits will hopefully last longer.

I will try experimenting with different speeds next to see whether fast or slow speeds work better.

Another quick update in case it helps anyone in the future: 

I did some experiments with drill speed and can confirm that the faster, the better (with my equipment, and when water cooled).

With the diamond drill bit on maximum speed, I have now got each hole down to ~10 minutes for a 1 pad hole. At half speed, it takes ~15 minutes, and at minimum speed it goes up to ~25 minutes. 

I think I have now exhausted all of the options and this is the fastest method possible with the tools that I have.

Final method:

All drilling is done inside a tupperware filled with water, do not use hammer mode. I place the tupperware inside a second tupperware to make sure that there is no chance of going through the tupperware and damaging the floor below. This is belt and braces: the chance of going through the first tupperware appears to be approximately zero. 

1) Start the hole with a carbide masonry drill, just to get enough of a hole to stop the diamond bit from wandering. This step can be a bit hit and miss. Some seem to work better with a 5.5mm bit, some prefer the 7.5mm bit. For some holds, I can do all of the starter holes in less than 5 minutes, for others it can take 15 minutes. I suspect the difference is the variation in the local geology of the gneiss. Seems to work best by starting at a slow speed, but ramping up to max as soon as there is the first hint of a hole in the surface. This step needs a fair bit of pressure on the drill.

2) Switch to the 6mm diamond core bit. Drill all the way through the hole. Use max speed. No need for any more than moderate pressure on the drill. Agitate the water to clear the hole of debris. Replace water once it gets too cloudy. A hose might work better to have constantly running water.

For particularly deep holds, I have to occasionally widen the hole slightly using the countersink bit, but this is not necessary for holds that are 1 pad or less. 

3) Finish off each hole with the diamond countersink bit so the washers sit nicely. This takes 30 seconds per hole.