This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1917 Excerpt: ...ROCK DRILLING IN SANDSTONE QUARRIES The two chief types of modern drills for quarry work are the tripod or bar drill and the jackhamer. The former is a reciprocating drill mounted on a tripod or attached to a bar that is supported by four legs. When the tripod is employed it must be moved to a new position for each ...
Read More
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1917 Excerpt: ...ROCK DRILLING IN SANDSTONE QUARRIES The two chief types of modern drills for quarry work are the tripod or bar drill and the jackhamer. The former is a reciprocating drill mounted on a tripod or attached to a bar that is supported by four legs. When the tripod is employed it must be moved to a new position for each hole that is drilled. When a bar is used, however, a line of holes may be drilled, the drill being moved along the bar and clamped successively in new positions. Bar or tripod drills are usually operated by steam. The jackhamer is a name given to a nonreciprocating drill operated without a tripod and provided with an automatic rotating de vice. It employs hollow steel bits, through which the exhaust passes and blows the cutting from the hole. It gives the best service when operated by compressed air. ADVANTAGES OF COMPRESSED AIR It has been found in most cases that compressed air affords certain advantages over steam for the operating of quarry machinery. Where steam is used in quarries there is usually a great deal of loss by condensation, and the variable temperature in the steam pipes makes it difficult to prevent leakage. As a result of these losses the effective pressure at the machine may be very much lower than the normal boiler pressure. When air is used the loss in pressure under similar circumstances is not nearly as great. Moreover, when drills are operated by steam, water must be supplied to the drill hole, in order to remove the cuttings. This arrangement requires extra labor and keeps the quarry floor wet or muddy. On the other hand, drills of the jackhamer type may be run dry. If steam is used for drills, and the quarry is of wide extent, it is better to have a number of boilers close to points where drilling operations are conduct...
Read Less
Add this copy of Infinite-Dimensional Topology: Prerequisites and to cart. £111.98, new condition, Sold by Bonita rated 4.0 out of 5 stars, ships from Santa Clarita, CA, UNITED STATES, published 1989 by North Holland.
