Dr. Howard S. White wrote:
>I bought the Harbor Freight $59 SDS Hammer Drill... and a $14 Grinder
>to cut off the end of one of the SDS bits to make it square.. used 5/8"
>heater hose and clamp as a guide followed the process
>Still no luck driving in the rods... must have hit rock of
>something....When we were putting in my tower, we had to jackhammer the
>clay(?) out of the hole as it was too hard for the backhoe to dig it
>I am still resisting the hydrallic method as I am concerned about the
>mess it will cause....
Ground rods are quite easily stopped by small rocks, but don't give up
on the SDS yet. You can buy drill bits up to 1.0 metre long, which do a
surprisingly good job of either breaking up the rocks or pushing them
out of the way. Use rotary + hammer action for this.
The bit needs to be about the same diameter as the ground rod - ideally
a little smaller. If the ground rod is a slack fit in the hole, it won't
have good contact with the dirt at first, though this will improve
slowly with time.
The very long, thin bits are quite wobbly when used at full length, so
it may be worthwhile to buy a 450mm one as well, and only switch to the
1.0m bit if the shorter one won't reach. (These are the European lengths
- I don't know what lengths are available in the USA. The 450mm bit is
designed to go right through a double brick wall with a cavity, and I
used mine yesterday to bring a TV antenna cable in... it was sooo easy.)
Deep drilling into clay can be very hard on the drill motor, because
clay clogs the bit very quickly and creates a lot of resistance. You may
need to pull out the bit to clean it after only a few inches of
progress.... but if you take your time, it will get you down to places
where a hammered rod won't go.
73 from Ian GM3SEK
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