Publisher's Synopsis
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. 1907 Excerpt: ...oil, roll the lap between these two hardened pieces of steel and the diamond will be forced into the lap. A lap of this description does its own grinding the same as an internal emery wheel, just grinding that part of the hole which runs eccentric, not following the hole the same as an ordinary emery lap does. One of the most important items to be observed when doing this grinding is not to force matters, especially if the lap is of a very small diameter, as it will tend to follow irregularities of the hole and the result will be unsatisfactory. The lap should just hit the high spots in the hole and gradually grind them off. By placing a screw-driver or some such tool against the grinder's foremost bearing, at the same time holding the handle against one's ear, the sound when the lap first comes in contact with the work can be readily detected. A more suitable tool for this purpose is shown in Fig. 70, it being termed a "harker"; it is nothing more than a piece of No. 30 drill rod inserted into a little piece of wood which is finished off to a suitable shape to hold against one's ear, the other end of the rod being split and spread fork shape so that it can be rested against the spindle or frame of the grinder. When grinding, if a lap is kept well lubricated with kerosene oil it will cut much freer and faster. Handling Diamond Charged Laps When doing this class of work it often happens that one must handle it entirely different from a larger piece. For instance, a piece of work 2 inches in diameter has a hole.040 in diameter; both must be accurately concentric with each other. Of course, if this were a larger hole it would be proper to grind the hole first and then place the piece on a true arbor and grind the outside, but this method would not be...
