CoA. Memos: Manufacturing and Production (1963-1965)
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Browsing CoA. Memos: Manufacturing and Production (1963-1965) by Author "Purcell, J."
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Item Open Access The application of the numerical method of evaluating the efficiency of grinding wheels and coolants for grinding nickel chromium alloy to specification E.P.K.31 (Henry Wiggin Ltd.) also the evaluation of surface residual stresses induced into the material by grinding: progress report no. 2(College of Aeronautics, 1963-12) Purcell, J.SUMMARY The material is presenting phenomena which though met and recognised previously the significance to the grinding process was on these previous occasions not critical. With this material, instead of a wheel life variation of 0.5% maximum there can be 3096 to 40% reduction in expected wheel life. A detailed explanation of this element of wheel face life will be included in the fine_ report when repeatable test results to substantiate the parley will be available. The test on soluble type coolants have not as yet been as successful as one would have hoped and it is intended to ask the supplier if an improvement can be made from the knowledge gained by the test here reported. The workpiece in all cases where soluble coolants were used remained cool, but with the very limited number of oil coolants some temperature rise in the workpiece is experienced. This temperature rise is not very critical if the workpiece is of sufficient surface area to allow cooling to take place more rapidly. The test piece used in the laboratory is 2.5 ins x 6 ins. long, and is now 0.5 ins. thick (originally 1.0 ins). The calculation is made and included for wheel specification Carborundum 5A 46/54 0.8 V.50 using Fletcher Miller Product M7/63 This is the first result which has given a performance life long enough to make these calculations and is included to enable any firm who must use results immediately to make use of our work. While not wishing to depreciate this product or to appear over enthusiastic I shall be surprised if improved life is not achieved but this fuller calculation will allow further appreciation of the numerical methods we are using.Item Open Access Machine tool laboratory: appendix A to progress report no. 2 on the investigation into grinding of nickel chrome alloy EPK31 produced by Henry Wiggins(College of Aeronautics, 19) Purcell, J.Introduction The work on the comparative tests of the effectiveness of coolants has continued. A wide range of soluble type coolants and straight oil coolants have been evaluated. The results of these tests are presented in a similar manner to that used in Progress Report Nos. 1 and 2, as Appendix A to Progress Report No. 2. From communications and inquiries in reference to the progress reports it may be that the clarity of the results could be improved to this end, more detailed attention to this is here included. Explanation of test results sheet headings. The Test Numbers, Wheel Type (specification Coolant, are all self explanatory. Grinding conditions This has been fully included in the progress reports, it is as follows: Table speed constant at 65 feet per minute Depth of cut constant at 0.001 ins. Gross feed constant at 0.042 ins. per table stroke Grinding wheel diameter maximum 7 ins. minimum 63/4 ins. Grinding wheel width 0.75 ins. constant. The grinding wheel specification and coolant are the variables, other conditions will be varied when initial testing is completed. The surface area ground. This heading means the area of surface ground under the standard conditions. per redress of the grinding wheel. All tests which achieve 75% of the previous test are repeated twice more. All products which achieve good results will be retested, and full calculations will be made. Full details and copies of results of any test are available on request. Surface finish The surface finish produced at each test is measured on the Taylor Hobson Talisurf. CLA is recorded, no trace record is made. This will be done when the most efficient products are retested. Where necessary brief remarks on a performance are included. These will be expanded and presented in greater detail when the final tests are made.Item Open Access A progress report on the application of numerically controlled grinding to the improvement of the fatigue strength of highly stressed ground gears(College of Aeronautics, 1963-07) Purcell, J.During the manufacture at the Bristol Aeroplane Works, of the research Aircraft, Bristol 1880 difficulty was experienced when attempting to grind sheets of stainless steel (spec. REX 443). The size of the sheets was 7 feet by 5 feet. A surface finish of not more than 10 micro inch CLA together with a thickness tolerance of 0.0002 inches was called for. This problem was put to a number of production engineerin&researchestablishments0 one, pf which was Cranfield. It was during the research work to find a solution to the above problem that a numerical method of evaluating the performance of grinding wheels, coolants, and the machinability of different materials was developed. This has now been further developed to enable the cause of the limitations in any grinding process to be diagnosed … [cont].