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Engineering literature on metalcutting fluids, 1971–1976
Engineering literature on metalcutting fluids, 1971-1976 J. O. Cookson* Comprehensive reviews of the literature concerned with cutting fluids are uncommon. Some of the most recent are contained in more general reviews covering, for example, tribology for the single year 1970,1 and in the ASME review of materials processing literature of which the latest part, 1971-72, was not published until 1976. 2 It is therefore convenient to present a further review covering the period 1971-1976. There may be a certain amount of overlap with the ASME review because a number of papers which are still of interest were published in the period 1971-72. Over any period it is inevitable that many useful general articles appearing in technical journals should become of less interest and lose their importance, particularly since they may well be replaced by more recent articles covering similar subjects. This review will concentrate attention on publications of more lasting and permanent value, ie reports of experimental work or surveys of the state-of-the-art having some real substance, together with a selection of the more recent, perhaps more general, descriptive material which could be of interest to the practising engineer. The literature dealt with is, by and large, intended for production engineers engaged in the practical application of cutting fluids, or for research workers engaged in production engineering, tribology, or related subjects. The emphasis placed upon, and the space devoted to, various aspects of the subject is more a reflection of the quantity of publications than a judgement on the relative importance of developments in the various areas.
State-of-the-art reviews and books Taken together, a number of articles published in 1971 provide a general state-of-the-art review of cutting fluid development and application at that time. They covered discussion of the advantages and disadvantages of waterbased 3 and synthetic fluids, 4 metalworking additives s and their functions, and the factors affecting the selection of cutting fluids, with recommendations on suitable fluids for various applications. 6 The technical background to the performance and application of cutting fluids, as seen from a German standpoint, was given in 1972 by a research worker of established reputation in metalcutting circles, Professor Keonig, in an article quoting 23 references. 7 Such general reviews have not been attempted in more recent years, although the proceedings of a one-day conference on synthetic cutting fluids in 1975 provides a commentary on the practical implications of developments in synthetic fluids, with papers on characteristics and performance, effects on seal materials and paints, disposal procedures, etc. 8 * MachineToollndustryResearchAssociation, HulleyRoad, Macclesfield, Cheshire SKI O 2NE, UK
Useful books have been sponsored by major oil companies, one devoted entirely to machine tools, metal cutting, and cutting fluids 9 and another containing a substantial section on these subjects. ~° Both give straightforward, practical advice for the machine tool user.
Cutting performance There are no simple, reliable tests giving generally applicable results for assessing cutting fluid performance. This is illustrated, for example, by reports from Standard Oil Company, Ohio, 11 where a laboratory drill test gave a different ranking of a series of oils than a controlled field test involving threadcutting. Furthermore, no relationship was apparent between operating performance and either common laboratory wear tests or the assessment of the active components in the oils from their known compositions. Some would say, however, that a tapping test can be used effectively in evaluating cutting fluid performance: it is evidently used for product development with success, as confirmed by field trials and commercial applications. Mobil Oil Research and Development Corporation, for example, claim a reproducibility of -+ 3%. 12 Others report tests with drilling only, developed into standard tests, for example by Gulf Research and Development Company, using an automatic drilling machine. 13 Other companies prefer to use a combination of tests. Authors from British Petroleum Company claim that a drill-life test and a tapping torque test prove to be nearest to meeting all the requirements. ~4 At the Esso Research Centre in Hamburg, a combination of two cutting tests has also been used to predict quickly the performance level and application range of/cutting fluids. ~s It is claimed that 25h work, 30 kg of workpiece material, and 5 litres of cutting fluid are required to produce performance charts for one fluid and one material. A re-drilling operation at constant-force feed and various cutting speeds and drill loads, with the feed rate and torque measured, is used to check cutting performance, and a threading operation at various speeds, with visual checks on surface roughness, to determine finishing performance. The British Petroleum Company has used a combination of tapping, drilling, and four-ball wear tests to evaluate the ep activity of chlorine-containing compounds in neat oils. This characteristic was regarded as a primary indicator of effectiveness in severe cutting operations. ~6 However, on the basis of laboratory machining tests and confirmatory broaching trials on Nimonic 90, another UK Company, Burmah-Castrol, concluded that the ep properties of an oil may not always be a reliable guide to cutting performance, since a non-chlorinated oil compared favourably with a chlorinated oil. 17 The results of tests comparing commercially available cutting fluids are rarely published, but one such report was
TRIBOLOGY international February 1977
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issued in 1974 by the Swedish Institute for Production Engineering Research, IVF, which carried out a number of tests including milling and deep-hole drilling. 18 Authors from the American test laboratory, Metcut Research Associates Inc, have provided a useful commentary on the machining tests used to evaluate cutting fluids. They give recommendations for the equipment, tools, workpiece material, test procedures, and tool-life criteria, as well as suggesting control-limits for the variables. ~9
Research into cutting fluid action During the period of this review, basic research into why and how cutting fluids function appears to have been fragmentary and scattered, apart from that which is revealed occasionally by cutting fluid manufacturers. One interesting piece of work was carried out at the University of Birmingham. 2° A metallographic method of estimating temperature gradients in cutting tools was used to demonstrate the influence of coolants on the temperature distribution in high speed steel tools used to cut nickel and iron. The most effective cooling action was shown to be through the tool body and coolant was directed to the hottest and most accessible faces, although differences between the machining characteristics of iron and nickel were found. At the University of Newfoundland, various concentrations of copper sulphate were used to machine Inconel X750. ~ The results showed lower cutting forces and reduced tool wear compared with conventional sulphurized oil. In Russia, claims have been made that the performance of cutting fluid emulsions is improved by inducing ultrasonic vibrations to increase the cooling properties 22.
Application of cutting fluids Recommendations for types of cutting fluids for various applications are given in the books mentioned previously,9'1° as well as in a recently revised edition of the Tool and Manufacturing Engineers Handbook. 23 A general article on metalworking fluids provides guidelines for selection as well as a tabulation of the leading cutting and grinding fluids available in the USA. 24 Recent trends in the development of cutting fluids are discussed in a brief article published in 1976. 2s A Swiss review of the application of mist cooling in the cutting of aluminium covers some 23 literature references and includes comment on the effects on tool life, on the design and operation of the spray devices, and on the cutting fluids available .26 In the later years of this review period, a number of articles have appeared, in various countries, extolling the virtues of mist cooling. Some, at least, of these articles describe one particular range of commercially-available fluids and equipment for producing the atomized mist spray. 27'28 The 'Hi-jet' method of cutting fluid application, using a high-pressure jet aimed through the clearance between tool flank and workpiece, was originally reported in the literature many years before the period covered by this review. More recently, experimental work has been done in Indian educational establishments on the optimum value of the supply pressure. 29 A helpful paper for those interested in the specialized aspects of the use of cutting fluids in deep hole boring was presented at a conference in 1975, 30 but only some of
56
TRIBOLOGY international February 1977
the figures and tables appear in the conference proceedings, without any text. The full paper, however, has been published in German. al In addition to information on fluid pressures and flow-rates, data is presented to show the influence of correct choice of oil on the costs of deep hole boring.
Abrasive machining Because of the differences in the details of the metalremoval process, it is usual to discuss grinding and other abrasive machining operations separately from the general run of metalcutting operations. Work on the comparison of grinding coolants has been undertaken by the Belgium research organisation CIRF and a grinding chart developed to provide a simple method of determining the optimum conditions for reducing the cost of grinding (as influenced by the chatterlimited ground volume, the metal removal rate, and the grinding ratio), reducing the residual stresses, and producing the required surface finish. Using data from a grinding test with a standard wheel in typical grinding conditions, emulsions, synthetic, and semi-synthetic water miscible fluids and neat synthetic oil were evaluated, showing advantages for the neat oil. 32 Russian experimental work on the evaluation of grinding fluids has been reported. 33 This also involved a standard procedure for grinding under controlled conditions. The criteria used were the grinding ratio, tangential grinding force, power, burn marks, surface roughness, and the maximum load achieved without burning. Unfortunately no test results are quoted. The introduction of techniques for using very high wheelspeeds in grinding has brought problems in the use of grinding fluids primarily as a result of the deflection of the fluid supply by an air-belt generated by the wheel. An extensive series of tests carried out at the Machine Tool Industry Research Association has been reported, a4 A number of inexpensive methods of effectively delivering fluid to the grinding zone were compared with the more expensive high-pressure jets previously found necessary. Two of the most successful methods were air jets, combined with a scraper-plate, and fins and other attachments to re-direct the air-belt in an axial direction to atmosphere. The test programme included the determination of the effect on grinding performance of changes in cutting fluid types between neat oil, light and heavy-duty soluble oil, and a chemical solution. Other research workers, at the University of Birmingham, analyzed in some detail the factors affecting the air layers, with measurements of air pressure and velocity, and studied the use of scraper blades. The design of fluid delivery nozzles was also studied and the critical velocity determined theoretically and experimentally, leading to the design of a more effective nozzle.3S Possibly influenced by the work on high-speed grinding, work is reported from Russia on the improvement of coolant application in internal grinding by eliminating air streams using a baffle fitted to the grinding spindle. 36 It is claimed that the choice of coolant type can have a significant effect on the grinding perforrrance of diamond wheels. A comprehensive review of the subject quotes the results of tests on a variety of workp~ece materials.37 More
detailed tests on the diamond grinding of tungsten carbide/steel combinations have also been reported, as There is little reference in the scientific literature to honing. A Japanese paper (written in English) on the development of in-process measurement of the 'loading' of honing stones to investigate the performance of various honing fluids is probably unique. 39 Another less-common operation, abrasive lapping, has been the subject of tests by Russian researchers seeking to determine the effects of various surfactants on metal removal rate. 4°
Oil mist Oil mist is the environmental health problem arising from the exposure of workers to cutting fluids which has been the subject of most comment in the engineering literature during the period of this review. Some disturbing medical evidence has been presented 41 and the situation in the UK has been studied by HM Factory Inspectorate. 42 The general subject has also been discussed in a number of articles: methods of dealing with the problem using oil mist extraction equipment have been described. 4a-4aPerhaps the only study including any detailed examination of oil-mist and air movements near the machine tool was carried out in East Germany.49 An alternative approach to the problem, the introduction of an anti-mist neat cutting oil, is described more recently s° and measurements have been made to show the total mist and oil mist levels for three types of water miscible cutting fluid, including an oil-less fluid, sl
Biodegradation During the period under review much attention has been given to problems of biodegradation of cutting fluids and to the use of biocides, but much had already been written in preceding years. In 1972 Bennett, in a comprehensive paper, surveyed 65 literature references to bring together the literature concerning the deterioration of cutting fluids and to present the information so as to be readily understood by those responsible for controlling cutting fluids. The subjects covered included microbes and other organisms capable of growth in cutting fluids, the effect of water variables, and the effects on the performance of the fluids, s2 The results of the examination of industrial samples of cutting oil emulsions for the purpose of identifying the dominant types of bacteria, and to check for potentially harmful bacteria, have been published fairly recently sa's4 as well as an explanation of some techniques for checking anti-microbial activity, ss The need for a standard laboratory test to predict the performance of a biocide when used in the metalworking fluid under plant conditions has been discussed, and test results comparing a proposed laboratory method with in-plant behaviour of a test biocide in a USA Army arsenal showed good correlation, s6 An interesting account of how one UK company dealt with the treatment of their central coolant plant is available, with the results of corrosion and microbiological studies before and after adding a proprietary biocide, s7 The control of bacterial contamination of cutting fluid systems is aimed at the maintenance of the system in good working condition and achieving an economic working life for the fluid. A practical and useful article, written for the user, discusses these aims in terms of the sources of contamination, bacteria types, and factors influencing their
growth, oil degradation and its practical significance, the identification of problems, the routine treatment of systems, and general workshop practice, ss A coolant evaluation chart has been suggested as an aid to keeping accurate records on performance, additions of water and additives, and test data on pH, oil/water ratio, bacteria counts etc, upon which effective action can be based, s9 In 1974 the Society of Manufacturing Engineers in the USA organised a series of papers to help manufacturing engineers prolong cutting fluid life. 6°-62 One of these papers 61 includes some comments on less-usual physical methods of protection from microbial attack, including ionizing radiation, thermo-pasteurization and sonic oscillation.
Filtration and cleaning Extending the useful life of fluids for indefinite periods is a claim made by an American company in relation to their methods and materials in a series of three fairly-recent articles which describe the use of stable coolants mixed with pure de-ionized water by automated proportioning equipment, coupled with the continuous removal of both solids and tramp oil. 63- 6s The quality of the water used to mix with cutting fluids is an important factor in prolonging fluid life. In an authoritative literature review, Bennett surveys 50 references up to 1974 and discusses aspects of the biological and chemical quality of water and some considerations that may improve coolant life. 66 Equipment for the filtration and cleaning of cutting fluids is also described in a number of other articles, 6~-~° while a further selection can be made of articles useful because they comment on problems, either in general terms ~t'rz or in relation to particular subjects such as aluminium swart~ or deep-hole boring and honing operations. 74 Few of the articles attempt any detailed guidance on the selection of methods or the evaluation of systems, but one 7s does attempt to deal with the probable acceptability of various systems for particular applications and another 76 includes formulae for use in calculating costs and savings from the use of filtration systems.
Disposal In 1973 Bennett published a thorough and authoritative review of pollution problems and disposal techniques. The case histories quoted cite the conversion of waste cutting oils into fuel oil, and petroleum emulsions into fertilizer and animal feed. T7 A paper by Bult s gives a more up-to-date account of methods of separation and disposal for water-based fluids, including some under development. An article describes an investigation into the economics of recovering oil from water-based cutting fluids by one particular method reverse osmosis. 7s
References 1.
Criticalreviews in tribology, 1970. Ed. D. Dowson. IPC Science and Technology Press Ltd., Guildford, 1972
2.
Reviewof materials processing literature 1971-72, Parts
3.
1-4. Ed. K. J. Weinmann. Journal of Engineering for Industry, February 1976, pp 1-29 Morton L S. Water-based fluids still a question. Industrial Lubrication and Tribology, February 1971, pp. 57-62
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33.
Thornhill F. H. Synthetic cutting oils. Industrial Lubrication and Tribology, February 1971, pp. 70-72 Nicholson R. A. Neat cutting oil and metalworking additives. Industrial Lubrication and Tribology, February 1971, pp. 63-66 Holmes P. M. Factors affecting the selection of cutting fluids. Industrial Lubrication and Tribology, February 1971, pp. 47-55, Koenig W. Technological principles with regard to the problem of cooling lubrication in metal cutting. Schmiertech. Tribologie, February 1972, pp. 7-12 Synthetic cutting fluids. Proceedings of a one-day conference, Machine Tool Industry Research Association, MacclesfieM, April 1975 Machine tools, metals and cutting fluids. BP Trading Ltd., London 1972 Lubrication in practice. Ed. by G. G. Evans et al. The Macmillan Press Ltd., London 1972 Webb T. H. et al Experience in field and laboratory evaluation of metal-cutting fluids. Lubrication Engineering, May 1974, pp 231-240 Ladov E. N. Tapping test for evaluating cutting fluids. Lubrication Engineering, January 1974, pp. 5-9 Holodnik E. Evaluation of cutting fluids with an automatic drilling machine. Lubrication Engineering, April 1974, pp. 195.200 Blanchard P, M. and Syrett R. J. Mechanical testing of cutting fluids. Lubrication Engineering, February 1974, pp. 62-71 Hensehen H. Laboratory screening test to evaluate the cutting performance of cutting fluids. Lubrication Engineering, April 1973, pp. 151-156 Mould R. W. et al. Investigation of the activity of cutting oil additives. Wear, January 1972, pp. 67-80: November 1972 pp. 269-286: October 1973 pp. 27-44: February 1974, pp. 267-271 Bezer H. J. and Oates P. D. Performance evaluation in cutting fluids using a laboratory machine tool. Lubrication Engineering, August 1973, pp. 336-340 Steen B. Cutting fluid performance and tool wear. IVF Resultat 74621, 1974, 8 pp Zlatin N. and Christopher J. Evaluation of the effectiveness of cutting fluids for industry. Lubrication Engineering, September 1973, pp. 402-405 Smart E. F. and Trent E. M. Coolants and cutting tool temperatures. Proc. 15th Int. Machine Tool Design and Research Conference, 1974 Amaria P. J. and Goosney R. J. Machining of titanium alloy steel Inconel-X750 using a soft metal electrolyte as cutting fluid. North American Metalworking Research Conference Proceedings, McMast er University, 19 73. Podurayev V. N. Improvement of the cooling properties of cutting fluids by inducing ultrasonic vibrations. Machines and Tooling, Vol. 46, No. 6, 1975 pp. 46-47 Tool and Manufacturing Engineers Handbook, 3rd edition. Ed. D. D. Dallas. McGraw-Hill, New York, 1976 Anon. Metalworking fluids. Manufacturing Engineer, November 1975, pp. 31-38 Cookson J. O. Cleaner cutting fluids cut costs safely. Metalworking Production, October 1976, pp. 183, 185, 187 Klein E. Kuehlschmierung durch fluessigkeitszerstaebung beim zerspanen yon Aluminium. Schweiz. Alum. Runsch. Vol. 22, No. 16, November 1972, pp. 360-371 Alger S. R. Challenge for mist cooling. South African Machine Tool Review, April 1975, pp. 6-7: May, p. 11 Alger S. R. Mists cool the cutting edge. American Machinist, May 15, 1975, pp. 69-70 Nagpal B. K. and Sharma C. S. Cutting fluids performance. ASME paper No. 72- WA/Prod - 9 for meeting November 26-30, 9 pp Zwingman G. Cutting oils for deep hole boring. Proc. of International Conference on deep hole drilling and boring. Brunel University, May 1975 Zwingman G. Kiihlschmier stoffe fiirdas Teifbohren. Industrie Anzeiger, 31st December 1974, pp. 2388-2391 Peters J. and Aetens R. An objective method for evaluating grinding coolants. Annals of the CIRP, Vol. 25/1, 1976, pp. 24 7-249 Egorov N. L and Barinov V. E. Proximate evaluation
58
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4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.
17. 18. 19. 20. 21.
22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32.
34. 35. 36. 37. 38. 39.
40. 41. 42. 43. 44. 45. 46. 47. 48. 49.
50. 51. 52. 53. 54. 55.
56.
57. 58. 59.
60. 61. 62.
procedure for the effectiveness of coolants during grinding operations. Russian Engineering Journal, v.L V, n. 4, 1975, pp. 55-56 High-speed grinding with particular reference to the proper employment of grinding fluids. Machine Tool Industry Research Association, MacclesfieM, 1973 Tnnal G. and Kali~ze~ H. Delivery of cutting fluids in grinding. Chartered Mechanical Engineer, September 1976, pp 95, 97, 98, 100 Khudobin L. V. Increasing the efficiency of coolants in internal grinding. Russian Engineering Journal, n. 11, 1975, pp. 54-56 Oates P. D. and Willmington H. M. How to choose coolants for diamond grinding operations. Industrial Diamond Review, September 1975, pp. 322-327 Thiel N. W. The wet grinding of tungsten carbide/steel combinations with diamond wheels. Industrial Diamond Review, January 1973, pp. 4-7 Yamamoto H. and Maedev Y. Inprocess investigation of honing stick loading under various machining fluids. Bulletin of the Japan Society of Precision Engineering, Vol. 8, No. 4, December 1974 How various surfactants affect abrasive lapping. Machines and Tooling, Vol. L V, No. 12, 1974, pp. 52-53 Waterhouse J. A. H. Cutting oils and cancer. Annals of Occupational Hygiene, Vol. 14, 1971, pp. 161-170 Annual Report of Her Majesty's Chief Inspector of Factories, 1971, p. 27and 1972,p. 67 Lywood J. G. The problem of oil mist pollution in factories. The Plant Engineer, December 1972, pp. 19-28 Forge alleviates oil-mist problems. Machinery, 12th September 1973, p. 365 Eliminating oil-mist. Tooling, August 1973, pp. 41-42 Agent Mistkop oil-mist filter installations. Machinery, 18th July 1973, pp 72-73 El'Yanov V. G. Removal of oil aerosols from ventilating air. Machines and Tooling, No. 8, 1973, pp. 59-60 Exhaust systems for cutting machine tools. IVF Resultat 74619, June 1974 Jaekel P. et al. Causes of development, physical properties, toxic effects, methods of measurement and removal of oil mist in metalworking industries. Fertigungstechnik und Betrieb, Vol. 24, 1974, No. 8, pp. 460-463 and No. 9 pp. 556-559 Keeling H. A. Checked your cutting oil lately? American Machinist, 7th January 1974, pp. 47-48 Cutting fluid study points to acceptable oil misting. Modern Machine Shop, Vol, 47, No. 7, December 1974, pp. 86-88 Bennett E. O. The biology of metalworking fluids. Lubrication Engineering, v.28, n. 7, July 1972, pp. 237-24 7 Wort M. D., Lloyd G. I. and Schofield, J. Microbiological examination of six industrial soluble oil emulsion samples. Tribology International, February 1976, pp. 35-37 Lloyd G., Lloyd G. I. and Schofleld J. Enteric bacteria in cutting oil emulsion. Tribology International, February 1975, p. 27 Hill E, C., Gibbon O. and Davies P. Biocides for use in oil emulsions - selection techniques for rolling mill coolants and cutting fluids. Tribology International, June 1976, pp. 121-130 Rogers M. R., Kaplan A. M. and Beaumont E. A laboratory in-plant analysis of a test procedure for biocides in metalworking fluids. Lubrication Engineering, June 19 75, pp. 301-310 Gatbutt J. Microbes can eat into coolant efficiency. Metalworking Production, October 1973, pp. 126-129 Lacaille W. F. Cutting fluid system maintenance. Tribology News, September 1975, issue 27, pp. 6-8 Kane E. L. A chart for recording and analyzing factors influencing coolant life. Lubrication Engineering, September 1973, pp. 391-395 Tomko J. Cutting fluid selection and maintenance factors which determine product longevity. Society o f Manufacturing Engineers, Paper MF74-170, 1974 Rossmore H. W. Microbiological causes of cutting fluid deterioration. Society o f Manufacturing Engineers, Paper MR74-169 Opaehak M. Central system and cutting fluid control
programmes. Society o f Manufacturing Engineers, Paper
MR74-157 63.
Wright J. H. Water quality and the performance of water miscible cutting and grinding fluids. Cutting Tool
71. 72.
Wells R. M. Filtration of machine tool coolants - is it time for new thinking? Filtration and Separation, January/February
73.
Axby R. E. Central coolant filtration-problems and solutions in the removal of aluminium swarf. Filtration and Separation,
Engineering, March/April 1975, pp. 5-8 64,
Sluhan W. A. Equipment for control and maintenance of water miscible cutting and grinding fluids. Cutting Tool
1974, pp. 65-6, 68-9
Engineering, May/June 1975, pp. 5-8 65. 66. 67. 68. 69.
Given D. G. Tramp oil control and maintenance when using water miscible cutting and grinding fluids. Cutting Tool
Engineering, September/October 19 75, pp. 4-8 Bennett E. O. Water quality and coolant life. Lubrication Engineering, November 1974, pp. 549-555 Cyclonic filtration system swallows swarf costs. Machine and Tool Blue Book, August 1975, pp. 78.80 Meninand B. and Barber S. J. Coolant filtration - Part II, A dozen ways to get clean. Factory, July 1975, pp. 26-29 Swarf clogs coolant and obstructs output. Metalworking
Production, July 1974, pp. 72-73 70.
Wringing extra value out of cutting fluids. Metalworking
Production, January 1972, pp. 64-65, 67-68
Brand R. H. Fluid longevity and central clarification systems.
SME Paper MR 74-171
November/December 1972 pp. 675-676, 678, 680, 714 74.
Knobloeh H. Coolant separation in deep-hole boring and honing. TZ f. prakt Metallbearb., November 1974, pp.
75.
Joseph J. J. What, why and when of coolant filtration systems.
409-412 Filtration and Separation, May/June 1975, pp. 259-262, 264, 266 76.
Joseph J. J. Cleaning coolants and lubricants by filtration.
Plant Engineer, 2nd November 1972, pp. 68-70 77.
Bennett E. O. Waste disposal of metalcutting fluids.
Lubrication Engineering, July 1973, pp. 300-307 78.
Stana R. S. and Markiand J. Reclaiming oil from coolants by reverse osmosis. Machinery and Production Engineering,
lOth December 1975, pp. 562.563
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TRIBOLOGY international February 1977
59
State-of-the-art reviews and books Taken together, a number of articles published in 1971 provide a general state-of-the-art review of cutting fluid development and application at that time. They covered discussion of the advantages and disadvantages of waterbased 3 and synthetic fluids, 4 metalworking additives s and their functions, and the factors affecting the selection of cutting fluids, with recommendations on suitable fluids for various applications. 6 The technical background to the performance and application of cutting fluids, as seen from a German standpoint, was given in 1972 by a research worker of established reputation in metalcutting circles, Professor Keonig, in an article quoting 23 references. 7 Such general reviews have not been attempted in more recent years, although the proceedings of a one-day conference on synthetic cutting fluids in 1975 provides a commentary on the practical implications of developments in synthetic fluids, with papers on characteristics and performance, effects on seal materials and paints, disposal procedures, etc. 8 * MachineToollndustryResearchAssociation, HulleyRoad, Macclesfield, Cheshire SKI O 2NE, UK
Useful books have been sponsored by major oil companies, one devoted entirely to machine tools, metal cutting, and cutting fluids 9 and another containing a substantial section on these subjects. ~° Both give straightforward, practical advice for the machine tool user.
Cutting performance There are no simple, reliable tests giving generally applicable results for assessing cutting fluid performance. This is illustrated, for example, by reports from Standard Oil Company, Ohio, 11 where a laboratory drill test gave a different ranking of a series of oils than a controlled field test involving threadcutting. Furthermore, no relationship was apparent between operating performance and either common laboratory wear tests or the assessment of the active components in the oils from their known compositions. Some would say, however, that a tapping test can be used effectively in evaluating cutting fluid performance: it is evidently used for product development with success, as confirmed by field trials and commercial applications. Mobil Oil Research and Development Corporation, for example, claim a reproducibility of -+ 3%. 12 Others report tests with drilling only, developed into standard tests, for example by Gulf Research and Development Company, using an automatic drilling machine. 13 Other companies prefer to use a combination of tests. Authors from British Petroleum Company claim that a drill-life test and a tapping torque test prove to be nearest to meeting all the requirements. ~4 At the Esso Research Centre in Hamburg, a combination of two cutting tests has also been used to predict quickly the performance level and application range of/cutting fluids. ~s It is claimed that 25h work, 30 kg of workpiece material, and 5 litres of cutting fluid are required to produce performance charts for one fluid and one material. A re-drilling operation at constant-force feed and various cutting speeds and drill loads, with the feed rate and torque measured, is used to check cutting performance, and a threading operation at various speeds, with visual checks on surface roughness, to determine finishing performance. The British Petroleum Company has used a combination of tapping, drilling, and four-ball wear tests to evaluate the ep activity of chlorine-containing compounds in neat oils. This characteristic was regarded as a primary indicator of effectiveness in severe cutting operations. ~6 However, on the basis of laboratory machining tests and confirmatory broaching trials on Nimonic 90, another UK Company, Burmah-Castrol, concluded that the ep properties of an oil may not always be a reliable guide to cutting performance, since a non-chlorinated oil compared favourably with a chlorinated oil. 17 The results of tests comparing commercially available cutting fluids are rarely published, but one such report was
TRIBOLOGY international February 1977
55
issued in 1974 by the Swedish Institute for Production Engineering Research, IVF, which carried out a number of tests including milling and deep-hole drilling. 18 Authors from the American test laboratory, Metcut Research Associates Inc, have provided a useful commentary on the machining tests used to evaluate cutting fluids. They give recommendations for the equipment, tools, workpiece material, test procedures, and tool-life criteria, as well as suggesting control-limits for the variables. ~9
Research into cutting fluid action During the period of this review, basic research into why and how cutting fluids function appears to have been fragmentary and scattered, apart from that which is revealed occasionally by cutting fluid manufacturers. One interesting piece of work was carried out at the University of Birmingham. 2° A metallographic method of estimating temperature gradients in cutting tools was used to demonstrate the influence of coolants on the temperature distribution in high speed steel tools used to cut nickel and iron. The most effective cooling action was shown to be through the tool body and coolant was directed to the hottest and most accessible faces, although differences between the machining characteristics of iron and nickel were found. At the University of Newfoundland, various concentrations of copper sulphate were used to machine Inconel X750. ~ The results showed lower cutting forces and reduced tool wear compared with conventional sulphurized oil. In Russia, claims have been made that the performance of cutting fluid emulsions is improved by inducing ultrasonic vibrations to increase the cooling properties 22.
Application of cutting fluids Recommendations for types of cutting fluids for various applications are given in the books mentioned previously,9'1° as well as in a recently revised edition of the Tool and Manufacturing Engineers Handbook. 23 A general article on metalworking fluids provides guidelines for selection as well as a tabulation of the leading cutting and grinding fluids available in the USA. 24 Recent trends in the development of cutting fluids are discussed in a brief article published in 1976. 2s A Swiss review of the application of mist cooling in the cutting of aluminium covers some 23 literature references and includes comment on the effects on tool life, on the design and operation of the spray devices, and on the cutting fluids available .26 In the later years of this review period, a number of articles have appeared, in various countries, extolling the virtues of mist cooling. Some, at least, of these articles describe one particular range of commercially-available fluids and equipment for producing the atomized mist spray. 27'28 The 'Hi-jet' method of cutting fluid application, using a high-pressure jet aimed through the clearance between tool flank and workpiece, was originally reported in the literature many years before the period covered by this review. More recently, experimental work has been done in Indian educational establishments on the optimum value of the supply pressure. 29 A helpful paper for those interested in the specialized aspects of the use of cutting fluids in deep hole boring was presented at a conference in 1975, 30 but only some of
56
TRIBOLOGY international February 1977
the figures and tables appear in the conference proceedings, without any text. The full paper, however, has been published in German. al In addition to information on fluid pressures and flow-rates, data is presented to show the influence of correct choice of oil on the costs of deep hole boring.
Abrasive machining Because of the differences in the details of the metalremoval process, it is usual to discuss grinding and other abrasive machining operations separately from the general run of metalcutting operations. Work on the comparison of grinding coolants has been undertaken by the Belgium research organisation CIRF and a grinding chart developed to provide a simple method of determining the optimum conditions for reducing the cost of grinding (as influenced by the chatterlimited ground volume, the metal removal rate, and the grinding ratio), reducing the residual stresses, and producing the required surface finish. Using data from a grinding test with a standard wheel in typical grinding conditions, emulsions, synthetic, and semi-synthetic water miscible fluids and neat synthetic oil were evaluated, showing advantages for the neat oil. 32 Russian experimental work on the evaluation of grinding fluids has been reported. 33 This also involved a standard procedure for grinding under controlled conditions. The criteria used were the grinding ratio, tangential grinding force, power, burn marks, surface roughness, and the maximum load achieved without burning. Unfortunately no test results are quoted. The introduction of techniques for using very high wheelspeeds in grinding has brought problems in the use of grinding fluids primarily as a result of the deflection of the fluid supply by an air-belt generated by the wheel. An extensive series of tests carried out at the Machine Tool Industry Research Association has been reported, a4 A number of inexpensive methods of effectively delivering fluid to the grinding zone were compared with the more expensive high-pressure jets previously found necessary. Two of the most successful methods were air jets, combined with a scraper-plate, and fins and other attachments to re-direct the air-belt in an axial direction to atmosphere. The test programme included the determination of the effect on grinding performance of changes in cutting fluid types between neat oil, light and heavy-duty soluble oil, and a chemical solution. Other research workers, at the University of Birmingham, analyzed in some detail the factors affecting the air layers, with measurements of air pressure and velocity, and studied the use of scraper blades. The design of fluid delivery nozzles was also studied and the critical velocity determined theoretically and experimentally, leading to the design of a more effective nozzle.3S Possibly influenced by the work on high-speed grinding, work is reported from Russia on the improvement of coolant application in internal grinding by eliminating air streams using a baffle fitted to the grinding spindle. 36 It is claimed that the choice of coolant type can have a significant effect on the grinding perforrrance of diamond wheels. A comprehensive review of the subject quotes the results of tests on a variety of workp~ece materials.37 More
detailed tests on the diamond grinding of tungsten carbide/steel combinations have also been reported, as There is little reference in the scientific literature to honing. A Japanese paper (written in English) on the development of in-process measurement of the 'loading' of honing stones to investigate the performance of various honing fluids is probably unique. 39 Another less-common operation, abrasive lapping, has been the subject of tests by Russian researchers seeking to determine the effects of various surfactants on metal removal rate. 4°
Oil mist Oil mist is the environmental health problem arising from the exposure of workers to cutting fluids which has been the subject of most comment in the engineering literature during the period of this review. Some disturbing medical evidence has been presented 41 and the situation in the UK has been studied by HM Factory Inspectorate. 42 The general subject has also been discussed in a number of articles: methods of dealing with the problem using oil mist extraction equipment have been described. 4a-4aPerhaps the only study including any detailed examination of oil-mist and air movements near the machine tool was carried out in East Germany.49 An alternative approach to the problem, the introduction of an anti-mist neat cutting oil, is described more recently s° and measurements have been made to show the total mist and oil mist levels for three types of water miscible cutting fluid, including an oil-less fluid, sl
Biodegradation During the period under review much attention has been given to problems of biodegradation of cutting fluids and to the use of biocides, but much had already been written in preceding years. In 1972 Bennett, in a comprehensive paper, surveyed 65 literature references to bring together the literature concerning the deterioration of cutting fluids and to present the information so as to be readily understood by those responsible for controlling cutting fluids. The subjects covered included microbes and other organisms capable of growth in cutting fluids, the effect of water variables, and the effects on the performance of the fluids, s2 The results of the examination of industrial samples of cutting oil emulsions for the purpose of identifying the dominant types of bacteria, and to check for potentially harmful bacteria, have been published fairly recently sa's4 as well as an explanation of some techniques for checking anti-microbial activity, ss The need for a standard laboratory test to predict the performance of a biocide when used in the metalworking fluid under plant conditions has been discussed, and test results comparing a proposed laboratory method with in-plant behaviour of a test biocide in a USA Army arsenal showed good correlation, s6 An interesting account of how one UK company dealt with the treatment of their central coolant plant is available, with the results of corrosion and microbiological studies before and after adding a proprietary biocide, s7 The control of bacterial contamination of cutting fluid systems is aimed at the maintenance of the system in good working condition and achieving an economic working life for the fluid. A practical and useful article, written for the user, discusses these aims in terms of the sources of contamination, bacteria types, and factors influencing their
growth, oil degradation and its practical significance, the identification of problems, the routine treatment of systems, and general workshop practice, ss A coolant evaluation chart has been suggested as an aid to keeping accurate records on performance, additions of water and additives, and test data on pH, oil/water ratio, bacteria counts etc, upon which effective action can be based, s9 In 1974 the Society of Manufacturing Engineers in the USA organised a series of papers to help manufacturing engineers prolong cutting fluid life. 6°-62 One of these papers 61 includes some comments on less-usual physical methods of protection from microbial attack, including ionizing radiation, thermo-pasteurization and sonic oscillation.
Filtration and cleaning Extending the useful life of fluids for indefinite periods is a claim made by an American company in relation to their methods and materials in a series of three fairly-recent articles which describe the use of stable coolants mixed with pure de-ionized water by automated proportioning equipment, coupled with the continuous removal of both solids and tramp oil. 63- 6s The quality of the water used to mix with cutting fluids is an important factor in prolonging fluid life. In an authoritative literature review, Bennett surveys 50 references up to 1974 and discusses aspects of the biological and chemical quality of water and some considerations that may improve coolant life. 66 Equipment for the filtration and cleaning of cutting fluids is also described in a number of other articles, 6~-~° while a further selection can be made of articles useful because they comment on problems, either in general terms ~t'rz or in relation to particular subjects such as aluminium swart~ or deep-hole boring and honing operations. 74 Few of the articles attempt any detailed guidance on the selection of methods or the evaluation of systems, but one 7s does attempt to deal with the probable acceptability of various systems for particular applications and another 76 includes formulae for use in calculating costs and savings from the use of filtration systems.
Disposal In 1973 Bennett published a thorough and authoritative review of pollution problems and disposal techniques. The case histories quoted cite the conversion of waste cutting oils into fuel oil, and petroleum emulsions into fertilizer and animal feed. T7 A paper by Bult s gives a more up-to-date account of methods of separation and disposal for water-based fluids, including some under development. An article describes an investigation into the economics of recovering oil from water-based cutting fluids by one particular method reverse osmosis. 7s
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Thornhill F. H. Synthetic cutting oils. Industrial Lubrication and Tribology, February 1971, pp. 70-72 Nicholson R. A. Neat cutting oil and metalworking additives. Industrial Lubrication and Tribology, February 1971, pp. 63-66 Holmes P. M. Factors affecting the selection of cutting fluids. Industrial Lubrication and Tribology, February 1971, pp. 47-55, Koenig W. Technological principles with regard to the problem of cooling lubrication in metal cutting. Schmiertech. Tribologie, February 1972, pp. 7-12 Synthetic cutting fluids. Proceedings of a one-day conference, Machine Tool Industry Research Association, MacclesfieM, April 1975 Machine tools, metals and cutting fluids. BP Trading Ltd., London 1972 Lubrication in practice. Ed. by G. G. Evans et al. The Macmillan Press Ltd., London 1972 Webb T. H. et al Experience in field and laboratory evaluation of metal-cutting fluids. Lubrication Engineering, May 1974, pp 231-240 Ladov E. N. Tapping test for evaluating cutting fluids. Lubrication Engineering, January 1974, pp. 5-9 Holodnik E. Evaluation of cutting fluids with an automatic drilling machine. Lubrication Engineering, April 1974, pp. 195.200 Blanchard P, M. and Syrett R. J. Mechanical testing of cutting fluids. Lubrication Engineering, February 1974, pp. 62-71 Hensehen H. Laboratory screening test to evaluate the cutting performance of cutting fluids. Lubrication Engineering, April 1973, pp. 151-156 Mould R. W. et al. Investigation of the activity of cutting oil additives. Wear, January 1972, pp. 67-80: November 1972 pp. 269-286: October 1973 pp. 27-44: February 1974, pp. 267-271 Bezer H. J. and Oates P. D. Performance evaluation in cutting fluids using a laboratory machine tool. Lubrication Engineering, August 1973, pp. 336-340 Steen B. Cutting fluid performance and tool wear. IVF Resultat 74621, 1974, 8 pp Zlatin N. and Christopher J. Evaluation of the effectiveness of cutting fluids for industry. Lubrication Engineering, September 1973, pp. 402-405 Smart E. F. and Trent E. M. Coolants and cutting tool temperatures. Proc. 15th Int. Machine Tool Design and Research Conference, 1974 Amaria P. J. and Goosney R. J. Machining of titanium alloy steel Inconel-X750 using a soft metal electrolyte as cutting fluid. North American Metalworking Research Conference Proceedings, McMast er University, 19 73. Podurayev V. N. Improvement of the cooling properties of cutting fluids by inducing ultrasonic vibrations. Machines and Tooling, Vol. 46, No. 6, 1975 pp. 46-47 Tool and Manufacturing Engineers Handbook, 3rd edition. Ed. D. D. Dallas. McGraw-Hill, New York, 1976 Anon. Metalworking fluids. Manufacturing Engineer, November 1975, pp. 31-38 Cookson J. O. Cleaner cutting fluids cut costs safely. Metalworking Production, October 1976, pp. 183, 185, 187 Klein E. Kuehlschmierung durch fluessigkeitszerstaebung beim zerspanen yon Aluminium. Schweiz. Alum. Runsch. Vol. 22, No. 16, November 1972, pp. 360-371 Alger S. R. Challenge for mist cooling. South African Machine Tool Review, April 1975, pp. 6-7: May, p. 11 Alger S. R. Mists cool the cutting edge. American Machinist, May 15, 1975, pp. 69-70 Nagpal B. K. and Sharma C. S. Cutting fluids performance. ASME paper No. 72- WA/Prod - 9 for meeting November 26-30, 9 pp Zwingman G. Cutting oils for deep hole boring. Proc. of International Conference on deep hole drilling and boring. Brunel University, May 1975 Zwingman G. Kiihlschmier stoffe fiirdas Teifbohren. Industrie Anzeiger, 31st December 1974, pp. 2388-2391 Peters J. and Aetens R. An objective method for evaluating grinding coolants. Annals of the CIRP, Vol. 25/1, 1976, pp. 24 7-249 Egorov N. L and Barinov V. E. Proximate evaluation
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procedure for the effectiveness of coolants during grinding operations. Russian Engineering Journal, v.L V, n. 4, 1975, pp. 55-56 High-speed grinding with particular reference to the proper employment of grinding fluids. Machine Tool Industry Research Association, MacclesfieM, 1973 Tnnal G. and Kali~ze~ H. Delivery of cutting fluids in grinding. Chartered Mechanical Engineer, September 1976, pp 95, 97, 98, 100 Khudobin L. V. Increasing the efficiency of coolants in internal grinding. Russian Engineering Journal, n. 11, 1975, pp. 54-56 Oates P. D. and Willmington H. M. How to choose coolants for diamond grinding operations. Industrial Diamond Review, September 1975, pp. 322-327 Thiel N. W. The wet grinding of tungsten carbide/steel combinations with diamond wheels. Industrial Diamond Review, January 1973, pp. 4-7 Yamamoto H. and Maedev Y. Inprocess investigation of honing stick loading under various machining fluids. Bulletin of the Japan Society of Precision Engineering, Vol. 8, No. 4, December 1974 How various surfactants affect abrasive lapping. Machines and Tooling, Vol. L V, No. 12, 1974, pp. 52-53 Waterhouse J. A. H. Cutting oils and cancer. Annals of Occupational Hygiene, Vol. 14, 1971, pp. 161-170 Annual Report of Her Majesty's Chief Inspector of Factories, 1971, p. 27and 1972,p. 67 Lywood J. G. The problem of oil mist pollution in factories. The Plant Engineer, December 1972, pp. 19-28 Forge alleviates oil-mist problems. Machinery, 12th September 1973, p. 365 Eliminating oil-mist. Tooling, August 1973, pp. 41-42 Agent Mistkop oil-mist filter installations. Machinery, 18th July 1973, pp 72-73 El'Yanov V. G. Removal of oil aerosols from ventilating air. Machines and Tooling, No. 8, 1973, pp. 59-60 Exhaust systems for cutting machine tools. IVF Resultat 74619, June 1974 Jaekel P. et al. Causes of development, physical properties, toxic effects, methods of measurement and removal of oil mist in metalworking industries. Fertigungstechnik und Betrieb, Vol. 24, 1974, No. 8, pp. 460-463 and No. 9 pp. 556-559 Keeling H. A. Checked your cutting oil lately? American Machinist, 7th January 1974, pp. 47-48 Cutting fluid study points to acceptable oil misting. Modern Machine Shop, Vol, 47, No. 7, December 1974, pp. 86-88 Bennett E. O. The biology of metalworking fluids. Lubrication Engineering, v.28, n. 7, July 1972, pp. 237-24 7 Wort M. D., Lloyd G. I. and Schofield, J. Microbiological examination of six industrial soluble oil emulsion samples. Tribology International, February 1976, pp. 35-37 Lloyd G., Lloyd G. I. and Schofleld J. Enteric bacteria in cutting oil emulsion. Tribology International, February 1975, p. 27 Hill E, C., Gibbon O. and Davies P. Biocides for use in oil emulsions - selection techniques for rolling mill coolants and cutting fluids. Tribology International, June 1976, pp. 121-130 Rogers M. R., Kaplan A. M. and Beaumont E. A laboratory in-plant analysis of a test procedure for biocides in metalworking fluids. Lubrication Engineering, June 19 75, pp. 301-310 Gatbutt J. Microbes can eat into coolant efficiency. Metalworking Production, October 1973, pp. 126-129 Lacaille W. F. Cutting fluid system maintenance. Tribology News, September 1975, issue 27, pp. 6-8 Kane E. L. A chart for recording and analyzing factors influencing coolant life. Lubrication Engineering, September 1973, pp. 391-395 Tomko J. Cutting fluid selection and maintenance factors which determine product longevity. Society o f Manufacturing Engineers, Paper MF74-170, 1974 Rossmore H. W. Microbiological causes of cutting fluid deterioration. Society o f Manufacturing Engineers, Paper MR74-169 Opaehak M. Central system and cutting fluid control
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Engineering, September/October 19 75, pp. 4-8 Bennett E. O. Water quality and coolant life. Lubrication Engineering, November 1974, pp. 549-555 Cyclonic filtration system swallows swarf costs. Machine and Tool Blue Book, August 1975, pp. 78.80 Meninand B. and Barber S. J. Coolant filtration - Part II, A dozen ways to get clean. Factory, July 1975, pp. 26-29 Swarf clogs coolant and obstructs output. Metalworking
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Infected oils infect The
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T h e y contaminate the machine. A n d the man w o r k i n g it. So Paul d e la Pena b a c k their high quality cutting oils with a c o m p l e t e p a c k a g e for their efficient maintenance : including Freddy, the mobile s u m p c l e a n e r ; Easicult, a simple slide test to monitor bacterial l e v e l s ; and a r a n g e of a d v a n c e d b i o c i d e s to stabillse infected emulsions. Paul d e la P e n a Limited, R a c e c o u r s e Road, P e r s h o r e , Worcs. WR10 2DD. T e l e p h o n e : 03865 2311 Telex : 339851.
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