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Dingus McGee
Social climber
Laramie
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Nov 29, 2011 - 08:01am PT
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One mechanism used in hammer drills to achieve their impact is by offset plate gears overriding each other. I took apart an old Makita hammer drill that quit working. It had two plate "gears" in which the teeth of the gears extended outward radially on the faces of the plates. One plate had torque delivered to it by the motor and other plate could slide along the z-axis to hammer on the bit but this plate could not rotate. The overriding of the power plate gears cause the impact but wears steel to steel which in this case had worn out the face plates.
A pneumatic rotary drill uses a reciprocating piston to compress air causing a small sliding cylinder(the Hammer) to fly against the bit anvil (this is what you see when you look into the back of the center of the SDS chuck. It is amazing that this little hammer can do so much rock crushing. These pieces involved in the rotary hammering show little signs of wear compared to equal time with a hammer drill.
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Dingus McGee
Social climber
Laramie
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Nov 29, 2011 - 08:20am PT
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Finding hardest rocks to drill can be a misleading experience. It turns out that some quartzites and amphibolites form a very small dust that both gum the carbide (lessening the bit impact) and do not auger very well. Since the carbide on the Hilti bits is butt brazed to the steel shaft and this friction heating causes the brazing to get close to melting leading soon to tip twist off. The carbide tip on the Bosch bits is brazed into a slot on the steel shaft and this design resists twist off torque much better than the $$$ Hilti. Sometimes switching bits styles can alleviate gumming and sometimes so can a fully charged battery with a new bit.
I have taken some of these "hard rocks" home where I could drill them with very high rpm using line 120 volts and seen no problems. The dust and gumming materials spun out.
The hardest rock to drill I have come across was a greenish amphibolite just south of University street in Spearfish, SD.
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Dingus McGee
Social climber
Laramie
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Nov 29, 2011 - 08:43am PT
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I have had a 24v Bosch bull dog, 3 gas rhyobi rotary drill, 3 Milwaukee 18v's Lithium and one Hilti 24v.
About the time of Lehman Brothers collapse I notice that prices on the Makita 18v lithium were at $130. After testing one I bought two more and got rid of all the above junk. This drill totally outperforms these dinosaurs of the past.
Contrary to what some have said that weight doesn't matter for rap drilling -- IT DOES. Ligther is better when doing overhangs. And so is longer.
The Makita comes in two versions: The Colinear chuck and motor shaft are better for rap bolting overhangs.
For drilling while leading the compact design with the motor shaft at a right angle to the chuck seem better or maybe the lightness of 14 v Makita would sever one best. I have little experience in this area.
Contrary to what Jim T says about weight the 18v Lithium Makita simply outperforms those behemoths of bigness that are out there. Don't go big unless you like to pack such crap(for dilling big holes often > 3/8" in granite) and you got the tool dirt cheap. Some of my friends have such heavies as the 36v Hilti's, 28v Milwaulee's and they are no fun on overhangs (they are pigs).
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Dingus McGee
Social climber
Laramie
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Nov 29, 2011 - 09:19am PT
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Yes,
that is great price for the Makita 18v lithium, it was originally $450.
I have put in over 3000 bolts with my most used one of these and it still cuts rock like butter.
Also you can put the tool in chisel mode only. You clean out those lose flakes inside cracks in no time (a trad tactic).
Or you can use the chisel for enhanced hold making on sedimentary rocks( a sport tactic).
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mynameismud
climber
backseat
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Topic Author's Reply - Nov 29, 2011 - 12:36pm PT
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Dingus, you da man. I bookmarked the Makita link. It looks like that is probably the way I will go. Light sounds good to me and it sounds like a solid recomendation that will hold up. I will be doing most if not all my bolting on lead and I like steeper climbs. I would rather it be a little less than perfect when rap bolting anchors and have it more ideal when on lead and a bit sketched. Dingus - I also really like the trad and sport examples that had me laughing good this morning with my coffee, nice way to start the day.
Jack, that is an awesome pile, enough to get me excited. However it looks like your bolting next to a perfectly good crack! :)
thanks everyone for all the input. This is a great. Never thought I would head up a thread like this.
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karabin museum
Trad climber
phoenix, az
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Nov 30, 2011 - 10:20pm PT
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For now I love my Dewalt 18V hammer drill. It has placed over one thousand bolts and is still running strong. Very light and compact. Great for 3/8 to 1/2 holes. Cost around 300.00 for the drill, charger, battery, case. What is cool is that additional batteries are only $50 each and the lithium are $80 each. Additional batteries for some of the bigger drills cost $280 and up for each. My 18V is a Hammer drill version, not a drill/hammer. New battery power gets qty 10 bolts in granite 3/8 x 4" summer, 6 bolts winter.
I used to use a 24V Bosch Bulldog which was wired with two 12V gel cell batteries. On one charge we drilled over 75 bolts. Gel cells at a battery store are relatively cheap compared to new mfg drill batteries.
For super anchor bolt holes 3/4" and over with depths to 18" I use a 36V Hilti.
Bolt on! Marty
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