A Practical Course of Instruction in The Science of Horology Or The Construction and Repair of Time-Measuring Instruments
By Orville R. Hagans and D. L. Thompson
(Continued From April, '46)
A flat steel burnisher, which is shown in Fig. 8, is used for burnishing or smoothing pivots. It is made in the same manner as the flat grinding slip, described in Article 4, of toolsteel or drill-rod, of 1/4" in diameter and about 3 1/2" in length, and hardened and tempered to a pale straw color, or it may be left hard. It should be filed to the shape shown in the figure; ground smooth on all faces on a flat stone; hardened; and then given a line finish on a coarse piece of emery paper which has been glued to a flat board. As an alcohol lamp and a blowpipe would not produce enough heat to properly harden such a large object, it will be necessary to heat this tool in a gas flame or a fire, such as a charcoal burner. It should be cooled endways to prevent it from warping badly, which can be accomplished by wrapping the end of a piece of iron wire around it with which it can be handled easily. It can be tempered on a flat strip of brass or iron held over an alcohol flame.
Fig. 8 shows the shape of a burnisher to be used on straight shouldered pivots. For coned pivots, one edge should be rounded off a little. For use on both small and large pivots, one edge should be rounded off only slightly and the other a little more so. The use of these burnishers will be shown and explained under the subject of pivot turning.
22. MAKING A ROUND OR NEEDLE-POINTED BURNISHER
A round burnisher, which is used for smoothing iron and brass pins, is shown in Fig. 9 It is made of a piece of tool-steel or drill-rod, of 3/16" in diameter and about 4" in length, by filing or turning to the shape shown, the tapered end being made about 11/4" long. If filed, the rod is held in a hand-vise and the end shaped on a filing block, as explained for taper filing in Article 6, and smoothed in the same manner with a hand stone, after which the tapered end is to be hardened and tempered to a pale straw color and then stoned smooth again. It should now be well polished on diamantine on a leather strip so that, when tested by running the little fingernail along it, no roughness can be detected anywhere on its surface.
If turned, it should be turned, tapered and then ground smooth with oilstone paste on an iron grinding slip, or with a hand stone, while rotating at moderate speed in the lathe, after which it is to be polished in the same manner, but using diamantine paste on a bell-metal slip. The use of this tool will be explained later.
23. MAKING A JEWEL BURNISHER
A jewel burnisher, which IS used for burnishing the bezel of a jewel setting over the edge of the jewel to hold it securely in place in the setting, is shown in Fig. 10. It is made of toolsteel or drill-rod, of 3/16" in diameter and about 4" in length, by turning or filing to the shape shown in the drawing, for about 1" of its length; grinding the face to an angle of 450; and then hardening the end for about 1/2". The face is then to be ground flat and the cylindrical section ground smooth for some distance back from the face, after which the face and ground section are to be well polished.
Another style of this tool is made by filing or turning to the same shape as shown in Fig. 10 and then filing and grinding the cylindrical section flat on opposite sides, leaving only a narrow flat strip of about 1/32" in thickness. The end is then ground to an angle of 450; the edge next to the point slightly rounded; the end hardened for about 1/2" and tempered to a pale straw color; and the face and rounded edge then given a high polish on dry diamantine on leather. The use of this tool will be explained under the subject of jeweling.
The student should make one of each of the burnishers above described for use later on in these lessons and to learn how to keep them in proper condition for use.