Polishing Procedure
Wax-coated laps sometimes undergo a brief breaking-in period during which the mirror may alternately slip and grab. Thickening the polishing mixture will help to alleviate this condition, although once the lap has been well charged with the polishing agent, it is desirable to work with as watery a mixture as possible.
The usual polishing stroke, which should be continued until all of the pits have been removed from the mirror, consists of a one-third diameter length used center over center, or it can be varied with a W stroke, in which the edges of the mirror are carried out to an overhang of about 1/2 on each side of the lap. The broken line in Fig. 30 indicates the path traversed by the center of the mirror in the performance of this stroke. When the lap is in good contact a perceptible drag will be felt, and some effort may be required in stroking.
As to pressure, it is difficult to prescribe the exact amount in pounds to be used. A considerable amount may be needed in order to overcome the polishing drag, but it will be less than was used in grinding. Any tendency of the mirror to skid or jump should be resisted. The mirror at all times should pass back and forth across the lap with the two surfaces kept absolutely parallel, and to do this the worker, and not the lap, should control the
mirror.
In order to handle the new technique better, your stance will have to be changed. In grinding, it was possible to stand up close to the work. In polishing, the feet should be spaced one back of the other, some little distance from the barrel. The pivotal action in executing the strokes should start at the feet or hips, not the shoulders or elbows, else there exists a tendency for the mirror to be rocked when the worker is reversing the direction of the stroke,
causing a turning down of the edge.
polishing procedure part 2 |
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