ided with a socketfor the reception of the end of the drill, to which it issecured by screws. The bits are of approximately tri-angular shape, terminating i:i sharp points at theirouter extremities. In practice a hole is first drilledwith a common drill. These drills are usually formedwith… … REAMER FOR ENLARGING BLAST HOLES. that in their rotation they will form an enlargedchamber, as indicated in the illustration. When thechamber has been reamed out to a sufficient depth, thedrill and reamer may be readily withdrawn, for thebits will return to their normal folded position. Mr.Henry C.…
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