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how to drill post holes in solid rock



 
 
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  #1  
Old March 7th 04, 06:37 PM
klim
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Default how to drill post holes in solid rock

I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep in
solid rock for steel T-posts for a fence and I haven't decided how to
go about it.

What type of bit/drill combination would be most cost effective?
Electric drill (size?) with core bit?
Pneumatic drill with impact bit?
Other combo?

The location is far from power so the job would require a portable
generator or a compressor if a pneumatic drill was used.

I have a 2hp 20 gallon compressor - would be sufficient to run a
pneumatic drill to drill the 1 1/2" holes?
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  #2  
Old March 7th 04, 06:39 PM
Joseph Meehan
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Default how to drill post holes in solid rock

klim wrote:
I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep in
solid rock for steel T-posts for a fence and I haven't decided how to
go about it.

What type of bit/drill combination would be most cost effective?
Electric drill (size?) with core bit?
Pneumatic drill with impact bit?
Other combo?

The location is far from power so the job would require a portable
generator or a compressor if a pneumatic drill was used.

I have a 2hp 20 gallon compressor - would be sufficient to run a
pneumatic drill to drill the 1 1/2" holes?



Call in the pros with the commercial equipment. It will be a lot
cheaper in the long run.



--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math



  #3  
Old March 7th 04, 06:49 PM
Toller
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Default how to drill post holes in solid rock


"klim" wrote in message
...
I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep in
solid rock for steel T-posts for a fence and I haven't decided how to
go about it.

I haven't any idea, but know enough to ask if it is granite or shale.


  #4  
Old March 7th 04, 07:20 PM
SteveB
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Default how to drill post holes in solid rock


"klim" wrote in message
...
I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep in
solid rock for steel T-posts for a fence and I haven't decided how to
go about it.

What type of bit/drill combination would be most cost effective?
Electric drill (size?) with core bit?
Pneumatic drill with impact bit?
Other combo?

The location is far from power so the job would require a portable
generator or a compressor if a pneumatic drill was used.

I have a 2hp 20 gallon compressor - would be sufficient to run a
pneumatic drill to drill the 1 1/2" holes?


Rent a core drill?

As suggested, it MIGHT be cheaper to have someone do it. It WOULD be a
whole lot easier. You might be opening a bag of snakes.

Steve


  #5  
Old March 7th 04, 07:23 PM
DanG
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Default how to drill post holes in solid rock

Way back when some friends and I generated a bid for 8' cyclone in
extremely rocky soil. A California company came in 40% lower than
any other local outfits. We went out to laugh thinking they would
not be prepared for local soil conditions. They had a heavy steel
dome, inserted approximately 1/4 stick of dynamite. When the
charge went off, the lid was upside down next to the hole ready
for the next load and the hole was clean to the bottom waiting for
the post and concrete.

Don't ever assume the low bidder is nuts. These guys went all
over the world setting fence.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Keep the whole world singing. . . .
DanG


"klim" wrote in message
...
I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep

in
solid rock for steel T-posts for a fence and I haven't decided

how to
go about it.

What type of bit/drill combination would be most cost effective?
Electric drill (size?) with core bit?
Pneumatic drill with impact bit?
Other combo?

The location is far from power so the job would require a

portable
generator or a compressor if a pneumatic drill was used.

I have a 2hp 20 gallon compressor - would be sufficient to run a
pneumatic drill to drill the 1 1/2" holes?



  #6  
Old March 7th 04, 08:00 PM
R.C. Crawford
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Default how to drill post holes in solid rock

Rent an 90 cfm air compressor and a drifter drill. Most equipmet rental
companies rent these items. Get a drill bit to fit the drifter that is equal
in diameter as the maximum size as your post. Then drill by going down about
6 inches and lifting the drill to within 1" of the top of the hole. continue
this until you reach the plan depth of your hole. Once at the bottom flip
the lever of the air drill to blow out the hole. There are usually three
positions for the operating lever on the drifter drill. There is one that
shuts it off. One that drills the hole and one that blows air to the bottom
of the hole to clean out the cuttings. It is important that when you rent
the drill, you show rent two drill bits. One is to be used to drill and the
other is to be used in case you lock up the first drill bit. If the first
bit gets locked in the hole, then simply use the second bit to drill beside
the other bit to relieve the pressure and remove the bit.
Wear heavy duty clothing and steel toe shoes when working. Safety glasses
are best due to the fact that the high pressure air will blow cuttings into
your face.

Make a plywood template that you can secure to the ground with your foot or
other item to hold the bit in place on unlevel ground. Becareful not to let
the plywood spin and cause injury.

Spend some time and plan a safe work experience. Expect the work to be very
energy consuming.
Watch for hand injury due to the vibration of the drill.

Good luck.

"klim" wrote in message
...
I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep in
solid rock for steel T-posts for a fence and I haven't decided how to
go about it.

What type of bit/drill combination would be most cost effective?
Electric drill (size?) with core bit?
Pneumatic drill with impact bit?
Other combo?

The location is far from power so the job would require a portable
generator or a compressor if a pneumatic drill was used.

I have a 2hp 20 gallon compressor - would be sufficient to run a
pneumatic drill to drill the 1 1/2" holes?



  #7  
Old March 8th 04, 12:39 AM
SQLit
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Posts: n/a
Default how to drill post holes in solid rock


"klim" wrote in message
...
I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep in
solid rock for steel T-posts for a fence and I haven't decided how to
go about it.

What type of bit/drill combination would be most cost effective?
Electric drill (size?) with core bit?
Pneumatic drill with impact bit?
Other combo?

The location is far from power so the job would require a portable
generator or a compressor if a pneumatic drill was used.

I have a 2hp 20 gallon compressor - would be sufficient to run a
pneumatic drill to drill the 1 1/2" holes?


You do not mention the type of rock. That makes a big difference.
Electric, Hilti or Bosh your going to need the biggest badest one they have.
You will probably wear it out when your done.

Pneumatic, You could let it run for a week, and probably burn it out and
still not have enough air for a pneumatic hammer. I used to work on a line
truck digging holes and setting poles. There was a air compressor on board
and a 90 lb pneumatic hammer. Set the truck rpms to 1800, then engage the
air pump by the PTO. Wait a few minutes and go to work. Took 20-30 minutes
to drill a 2 inch hole in granite 2 feet deep.

I do not think that the 6 inch holes are deep enough for a regular fence
post. More like a foot or more will be needed.

Have fun your in for some long hours.


  #8  
Old March 8th 04, 02:19 AM
klim
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Default how to drill post holes in solid rock

On Sun, 7 Mar 2004 17:39:57 -0700, "SQLit"
wrote:

[snipped]

I do not think that the 6 inch holes are deep enough for a regular fence
post. More like a foot or more will be needed.

Have fun your in for some long hours.

Thanks for the experienced replies. It is granite rock here in the CO
foothills and steep. Pneumatic sounds like the way to go to drill
holes. But it does sound as arduous as I feared especially considering
I'd need about 300' of hose to reach some of the places.

But, I'm also considering an alternative plan and I'd appreciate any
comments on it. A buck fence made out of 2" used well pipe. I can weld
the A-frames in my shop, haul them up the mountain and weld the rails
in place with my 110v wire feed welder and a portable generator.
Materials would cost more than a T-post and smooth wire fence, but
this might be easier to build in the long run. Any thoughts?
  #9  
Old March 8th 04, 03:21 AM
RB
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Default how to drill post holes in solid rock

I had to drill a large number of 1-1/4" holes 15 inches deep in granite
to place a dock two years ago. The local Makita rep offered me the loan
of a Makita HR3851 rotary hammer and with it I was able to drill them
quite easily.

Your compressor isn't big enough to run a pneumatic drill of any size
but would be useful to clean out the holes. The bit doesn't lift
granite dust well from deep holes. I fashioned a 1/4" diameter copper
tube that would reach to the bottom of the hole and attached it to an
air chuck. Every couple of inches I'd pull the bit back, insert the
tube and clear the hole. (Eye protection and a dust mask were needed.)
Not a bad job. No more than 10 to 15 minutes per hole, including beer
breaks.

RB

klim wrote:
I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep in
solid rock for steel T-posts for a fence and I haven't decided how to
go about it.

What type of bit/drill combination would be most cost effective?
Electric drill (size?) with core bit?
Pneumatic drill with impact bit?
Other combo?

The location is far from power so the job would require a portable
generator or a compressor if a pneumatic drill was used.

I have a 2hp 20 gallon compressor - would be sufficient to run a
pneumatic drill to drill the 1 1/2" holes?


  #10  
Old March 8th 04, 02:21 PM
PJx
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Posts: n/a
Default how to drill post holes in solid rock

On Sun, 07 Mar 2004 18:39:01 GMT, "Joseph Meehan"
wrote:

klim wrote:
I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep in
solid rock for steel T-posts for a fence and I haven't decided how to
go about it.

What type of bit/drill combination would be most cost effective?
Electric drill (size?) with core bit?
Pneumatic drill with impact bit?
Other combo?

The location is far from power so the job would require a portable
generator or a compressor if a pneumatic drill was used.

I have a 2hp 20 gallon compressor - would be sufficient to run a
pneumatic drill to drill the 1 1/2" holes?



Call in the pros with the commercial equipment. It will be a lot
cheaper in the long run.


Don't be such a weenie. That is not what alt.home repair is all
about.
Pj


 




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