From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Specifications and testing procedures for hard composite dielectrics and insulating materials, including tool wear and chipping tests.
| Identifier | ExFiles\Box 24\2\ Scan215 | |
| Date | 21th February 1922 guessed | |
| HARD COMPOSITE DIELECTRICS (INSULATING MATERIALS). 573 be employed. If a specimen of these dimensions is not obtainable another form of specimen may be used, provided a total length of cut of 1 600 ft. can be made on the specimen. so as to obtain the equivalent of one continuous cut 1 600 ft. long. The cut shall be made under the following conditions :— Cutting speed .. .. = 100 ± 5 ft. per minute. Depth of cut .. .. = 0.020 ± 0.002 inch. Revolutions per inch of feed .. .. .. = 64. Temperature of the specimen .. .. .. = 20° C. ± 2.5° C. (b) Tool. The cut shall be made with the following tool :— Form .. .. .. See Fig. 15. Material .. .. .. Silver steel. Diameter .. .. .. ⅛ inch. Tool angle .. .. .. 45°. Front clearance .. .. 45°. Top rake .. .. .. 0°. Temper .. .. .. Glass-hard in clean cold water, and left with a good cutting edge. All materials should be tested dry. If, however, it be desired to obtain results with lubricant, the same test shall be employed, and a definite lubricant shall be specified by the manufacturer of the material for the purpose of the test. When reporting on a material tested with lubricant, full particulars of its composition and the rate of flow of the lubricant during the test shall be stated. Fig. 15.—Form of Tool for Tool Wear Test. Fig. 17.—Form of Tool Holder for Tool Wear and Chipping Tests. The tool shall be finished on a fine oilstone, using a jig to ensure obtaining the specified angle and accurate shape. The angle θ at which the tool is set to the axis of the specimen shall be adjusted so that the wear is substantially at the end of the tool (see Fig. 16). Fig. 16.—Setting of Tool for Tool Wear Test. The tool shall be set accurately centrally so that the plane of its upper face contains the axis of rotation of the specimen.* (c) Conditions. The surface of the specimen shall be made parallel before each cut, so as to remove the taper produced by the previous tool wear. After each cut, the depth of the fresh cut shall be reduced at the start by an amount corresponding to the radial wear of the tool. * A suitable form of tool holder is shown in Fig. 17. 14. Chipping. (a) Specimen. For the purpose of grading the material with respect to chipping, a taper cut shall be made on a rod 5 inches long and not less than 1 inch, or more than 2 inches, diameter. The specimen shall be turned parallel before the taper cut is made. The chipping constant for the material shall be the depth of the cut in inches multiplied by the diameter of the specimen in inches, at the point where chipping commences. | ||