Browsing 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 An interim note on machining super high tensile steel(College of Aeronautics, 1958-09) Purcell, J.; Ellis, P.J.; Vicary, D.P.A series of tests have been carried out to determine the machinability characteristics of Ultra High Tensile Steels in the 120 tons sq. ins. T/S range with hardness values of 550 to 600 V.P.N. Tool geometry and cutting conditions for end and face milling, drilling and tapping were investigated. A basic approach to tapping tests and tap design was developed. Short descriptions of the tests and a graphical presentation of the results are included. These show optimum conditions and the very critical nature of the variables on tool efficiency for the processes of drilling and end and face milling, under finishing conditionsItem Open Access Machinability investigations into special materials. Part 1 stainless steel Rex 448 hardened and tempered to Brinell minimum 321, maximum 375(College of Aeronautics, 1954-11) Purcell, J.This Report deals with the machinability of Firth-Vickers materials. Reference REX WO (Stainless Steel) in the hardened and tempered condition* U,T.S 70-75 tons; Brinell hardness 321 minimum, 375 maximum. CONTENTS: SECTION 1 The development of a single point cutting tool (Lathe Tool). SECTION 2 The application of this tool to the turning process to determine the optimum surface speed and best feed rate. SECTION 3 The determination of the life of the cutting tool when used at optimum surface speed and best feed. SECTION 4 The modification of the single point tool to meet a special requirement; i.e. to be applied as a single tooth in a face milling cutter which is suitable for use when face milling Rex 1018 sheet in the hardened and tempered condition. The machining process must be designed to result in the minimum distortion in the finished component and give a good surface finish. Further, it is desirable that the finished dimensions shall be achieved at one pass and an area of 32 square feet be covered between re-grinds of the milling cutter. SECTION 5 Conclusions. SECTION 6 Results of practical application. Report on results of the application of the proposed cutter design, etc.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 note on an investigation of the surface grinding process with examples of wheel and coolant selection and planning data(College of Aeronautics, 1956-02) Purcell, J.This note deals with an investigation into the establishment of manufacturing techniques, on a production scale, for surface grinding, high tensile heat resistant alloy sheet approximately 7 feet by 5 feet. Rigid manufacturing tolerances are demanded in which surface finish must not exceed 10 micro-inches and the thickness tolerance is plus or minus 0. 0002 inches. The information contained in this report applies to the surface grinding process in general and can be used to aid production planning, as a correct estimate of wheel life when operating under set conditions can be made, and the necessary time for redressing allowed. Results from the work carried out suggest that it may be beneficial to pass components to be surface ground under a roughing wheel (Lumsden) type machine, which will set the constant metal thickness for final finishing. In this way a correct estimated time could be allowed for the operations roughing and finish grinding at optimum conditions.Item Open Access A note on surface grinding :|bstayblade, in the fully hardened and tempered condition UTS, 80 tons per sq. in., V.P.N 390.(College of Aeronautics, 1957-01) Purcell, J.SUMMARY The investigation carried out into surface grinding Stayblade shows that this material presents severe conditions to the grinding wheel, and the grinding wheel face is broken down fiarly quickly. The method described in C of A Note 38 for wheel and coolant selection and development enabled the total wheel face life to be improved from 0.105 cubic ins. to approximately 10.00 cubic ins, per redress with acceptable surface finish. The use of soluble typos of coolants would appear to be much less efficient than cutting or grinding oil coolants and the following combinations were found best:- Wheel:- Carborundum 7.D.A.60 I 5 IN BILT. Coolant:- Manchester Oil Refinery DOLPHIN MC OIL. Wheel life is 3.5 cubic ins. per redress for 7 ins. dia. by 1 in. wide wheel. The addition of 5% Wynns friction proofing fluid showed 200% increase in wheel face life with acceptable surface finish.Item Open Access A note on the machinability of ultra high tensile steel(College of Aeronautics, 1957-01) Purcell, J.The requirements of this investigation were to determine optimum tool geometry and cutting conditions for turning Ultra High Strength Alloy Steel (fully heat treated to 120 tons per sq.ins.). The material will be used for bolts, whose screw threads will be produced by thread rolling. Dimensional accuracy required on the blanks is 0.0002". The material in the above state presents extremely severe conditions, especially on the nose of the turning tool, and results in rapid wear and loss of dimensional accuracy. Application of cutting coolants or lubricants made no measurable improvement on tool nose wear, benefits gained from the use of coolants being confined to reduction of flank wear.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].Item Open Access A report on a series of tests carried out to determine the suitability of the grinding process for evaluating the efficiency of coolants to be used on the metal cutting processes process for evaluating the efficiency of coolants to be used on the metal cutting processes and also to evaluate the relative efficiency of 4 coolant samples for the drilling and turning processes(College of Aeronautics, 1966-04) Purcell, J.A test programme was to be carried out to evaluate a series of additives for use in industrial metal cutting coolants for use initially on the turning, drilling and milling processes. These tests when they take the form of tool life tests are costly in time and material and where a shorter test can be reliably substituted for a life test, this is most desirable. To this end the grinding process was included in a pilot scheme to try to relate the grinding results to the drilling and turning results. Milling was not used in this pilot scheme. The grinding process has been very extensively studied at the College of Aeronautics during the past 10 years and a reliable method of evaluating the performance of grinding wheels and coolants has been developed and proved in a very wide range of industrial applications. The time required to evaluate a wheel or coolant sample is approximately 1 hour and the material consumed would be a few ounces in weight, hence, the desire to interpret coolant efficiency for the metal cutting processes from tests carried out using the controlled grinding process. (See ref. 1).Item Open Access A report on the survey carried out at W. H. Allens, Queens Works, Bedford(College of Aeronautics, 1966) Purcell, J.The original terms of reference under which the project was undertaken are included in this report and the requirements requested are satisfied. On initial contact at Aliens, I was introduced to Mr. Colson, who informed me that his company of Consulting Engineers had introduced a scheme of methods engineering work study and incentives payment and that the results on the grinding section were not fully satisfactory. The machine loading was based on synthetics which were working in other factories. There was methods and planning charts from which the Methods Engineering and Planning Sections worked when loading work onto the shops and it was required that the shortcomings of these charts should be corrected. I was then introduced to Mr. Sargent, Chief Methods Engineer. He assigned one of his staff to me. It was suggested that we went down to the shop floor and consider the Lumsden grinding machine, as this machine stalled when the feeds and speeds suggested from the methods sheets were applied, but the main problem which it was essential to tackle as soon as possible was the grinding of gudgeon pins. Details of the work carried out on each machine are included in separate sections.