Author Description

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. 1908 Excerpt:...head must butt against the end of the driven tube, so that the driving blow is not transmitted through the screw threads on the tube end. The mall is operated by the same rope and in the same manner as the boring tools when the hole is shallow. The stroke is usually about 3 feet, and the mall is fed down on to the driving head by lowering off the bull wheel shaft. The auger or boring chisel is shown in Fig. 4. The working part of the tool is fairly hard steel of flat section, slightly hammered out at the ends and chisel-pointed. Down the centre of each flat Fig. 5. side of the chisel is cut a semicircular groove to give clearance. The auger has a tapered screwed end for attachment to the auger stem (see Fig. 5). The shoulder of the auger is slightly recessed, Bo that when screwed home on the auger-stem contact is made on the edge of the circumference of its section. The diameter of the shoulder for a 14-inch hole is about 5 inches. The auger-stem which guides the auger and gives weight to the blow is a bar 4J inches in diameter and 30 feet long, fitted at the bottom with a female end to take the auger and at the top with a male end for the rope or " jar " attachments. A "jar" is a most important item in the list of boring tools, and always forms part of the string of tools when the hole is over 150 feet deep. Its construction will be seen in Fig. 6, and its function is to enable an upward blow to be struck on the auger stem should the auger stick in the hole. A sinker bar 4£ inches in j, diameter by 15 feet long is screwed on to the top half of the jars and gives weight to the upward blow. Light jars are provided for use with the sand pump when it is thought that there is any risk of the pump sticking. It will be seen that the jars...