Hand drilling.

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deSouzaFrank
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Hand drilling.

Post by deSouzaFrank » Tue Aug 02, 2016 12:37 pm

Hi

Ive been placing a few bolts at a crag near me, all placed by drilling by hand. Im an artisan by trade so hammering is really no big deal to me anymore but ive managed to sink a 10mm drill 120mm deep in about 15minutes. This had me thinking about the quality of the rock. It might be too soft.

So if you have drilled by hand, how long did it take you on average to drill a hole? Im no geologist and would really just like to put my mind at ease to find out if this rock is ok.

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Nic Le Maitre
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Re: Hand drilling.

Post by Nic Le Maitre » Tue Aug 02, 2016 1:00 pm

If you're worried about the softness then the bigger and deeper the hole the better. Use glue ins rather than expansions as their cone of failure is much larger. You can make a bodge pull tester using a chain, a crowbar and a bottle jack. You will need a second pair of hands to help though. It will only give you the tensile load capacity of the bolt (i.e. the resistance to an outward pull) but the strength in shear (usual loading for a fall, perpendicular to the bolt) will be far greater.
Happy climbing
Nic

deSouzaFrank
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Re: Hand drilling.

Post by deSouzaFrank » Wed Aug 03, 2016 10:43 am

Thanks Nic.

The bottle jack is obviously to try and jack the bolt out of the wall. I'm assuming the chain is to be attatched to the bolt to try and jack it out. The crowbar? What kind of bottle jack though too. Surely a 50ton is over kill?

SNORT
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Re: Hand drilling.

Post by SNORT » Thu Aug 04, 2016 9:32 pm

1cm is 10 minutes in hard quartzite.

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Nic Le Maitre
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Re: Hand drilling.

Post by Nic Le Maitre » Fri Aug 05, 2016 8:16 am

Hi Frank

I'd get a cheap 1 or 2 tonne one from Midas.

Chain on the bolt. Chain attached to the crowbar. One end of the crowbar rests on the rock the other rests on the top of the jack and away you go. Depending on how you arrange the order, you will end up with a Class 2 or 3 lever.

Image

You can then work out how much force you are putting on the bolt using the lever equation: MA = a/b and your input force.
Happy climbing
Nic

Gregor
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Re: Hand drilling.

Post by Gregor » Tue Aug 09, 2016 8:06 pm

I have a similar experience as Snort above i.e. 90 min for a 90cm hole, but I've only drilled a few holes with the Rocpec. Of course, the time depends on a few factors e.g. a good vs awkward body/hammering position; drill bit sharpness; weight of the hammer; efficiency etc. I used a standard hardware store american claw hammer, which is around half a kg. That is about what the Petzl Tam Tam weighs, which is designed for hand drilling. There must be a risk of rock fracture if using a much heavier hammer.

On Youtube there's a guy with loads of experience who makes a decent hole in about 15mins I think. That's with a custom sharpened drill bit and hammer, in a easy body position.

I also wasn't sure how often to pump the hole out, so I stopped after every 10 to 20 hits (also for rest!). The guy on the video didn't stop much.

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