In a message dated 11/9/2006 9:10:44 A.M. Central Standard Time,
[log in to unmask] writes:
I suggest that it would be unlikely that 6ft holes would drilled under
normal circumstances due to the severe fall off in penetration rate due to
the shock losses in the steel and the problems of hole cleaning except in up
holes.
With hand drilling the miner would not be drilling a round as we know it
today so in most circumstances there would be no reason to go for long
holes.
Tony Brooks
Martin,
Tony is correct in his statement. This would apply to a man single jacking
(one man hand drilling). In single jacking, the usual depth was not over 30
inches, more like 20 -24 inches. Rate of blow would be around 20-30 blows per
minutes. In contests it would run 60 plus blows per minute as was seem in the
big contest glory days of Butte, Montana. It usually came down to Cornishmen
versus Irishmen.
I assume you are talking about a single jack driller. Hole size rarely over
1-1/4 inches in diameter. Size of hole would determine production.
In granite a good guess would be between 6 inches to 2 feet per hour of
drilling penetration. I guess it depended on the driller, size of hole, hardness
of the granite and his interest to work that day.
Jim Besleme
Columbia, Missouri
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