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A Selection of Notes on Recent Equipment and New and Well-tried Methods and Materials New Euco Micrometer Spacing Collars necessary to dismantle the arbor by removal of steadies, collars, shims and cutters, in order to re-set When the Euco Ground Thread Micrometer with slightly different size collars and shims in an Spacing Collars were introduced a few years ago, the effort to eliminate the errors. Even when the machine only sizes produced were for 1 in. and 1¼ in. arbors produces correctly the whole procedure must be and the minimum width 13/16 in, A few months later, repeated on each occasion that wear on one or more the company extended the range to cover 1½ in. dia. of the cutters takes place. arbors and introduced a narrow type micrometer This new micrometer spacing set removes the spacer having a minimum width of ¼ in., also avail- necessity for constantly disturbing the set up, by able for arbors up to 1½ in. dia. Continental inquiries affording means accurately to control the various resulted in the range being extended to cover 16 mm., spacing dimensions without dismantling. This is 22 mm., 27 mm., 32 mm., 40 mm., 55 mm. and 60 mm. accomplished by always using the micrometer spacer with metric calibrations 0·01 mm. As many foreign in conjunction with the standard solid collars when industrial concerns were using British and American preparing the set up. For instance, for a spacing machines, a further demand developed for the strength of screw thread is worth noting. Resistance dimension of 27/32 in. the setter would use a standard English sizes with metric readings, so the range was of threads to shear is given by πN(Dm+2L)(P—2r collar ⅜ in. wide and set the micrometer spacer to give again extended. sin 62½°) ft. the balance, i.e. 15/22 in., at the same time making The company is now also manufacturing micro In the case of the micrometer spacer for a 1 in. adjustment for machining limits. Subsequent errors meter spacers for 2 in., 3 in. and 4 in. dia. arbors. dia. arbor due to worn cutters, or other causes, can be im- The minimum width of these extra large sizes varies N =number of threads in engagement=10 mediately corrected by simply slacking off the arbor from 13/16 in. for the 2 in. dia. arbor, to 1¼ in. for the Dm = minor diameter = 1·28 in. locknut and turning the calibrated sleeve of the 4 in. dia. arbor. L =r-(r cos 62½°) = 0·00185 in. micrometer spacer. This sleeve is machine divided The future programme is to continue the manu r = radius of thread = 0·00343 in. in steps of 0·0005 in. and, as the clearly cut engraved facture of the popular ¼ in. wide micrometer spacer P =pitch = 0·025 in. lines arc comfortably open, being approximately for arbors up to 1½ in. dia. and to replace the 13/16, in. ft = tensile strength of material =291,200 lb. ⅛ in. apart, close adjustments may be carried out with wide model by a new type with a minimum width Evaluation of the above makes it apparent, that ease, even to limits as fine as 0·00025 in. of 7/16 in., also available for arbor diameters up to several tons pressure would need to be employed, in The micrometer spacing set in FIG. 1 is claimed to l½in. which event, the weakest part of the arbor would snap be the only one of its type in the world. It includes a FIG. 1 shows the new Euco micrometer spacing set first. supply of steel shims from 0·002 in. to 1/16 in. in width, for the three standard English and American arbor The sets are available in the following sizes listed a progressive range of hardened and ground steel sizes of 1 in., l¼ in. and 1½ in. expressly designed below: collars from ⅛ in. to 1 in. in width, together with the for the setting up of milling machines. essential micrometer spacer made from special tool Set No. Bore (in.) Micrometer Price When two or more cutters require assembling on a steel, hardened and ground throughout, including the Width (in.) £ s. d. milling machine, the usual method is to use solid internal and external micrometer threads, which arc collars between cutters to give the exact dimensions A.100 1 5 15 0 7/16 produced on modern thread grinding machines. needed, the assembly then being clamped and a trial A. 125 6 9 0 1¼ 7/16 cut made. Theoretically the machined dimensions The manufacturers arc often asked about the A.150 7 5 0 1½ 7/16 should, of course, coincide with the precise spacing possibility of micrometer threads collapsing under S.100 1 5 5 0 of the cutters, but due to discrepancies that may exist the pressure used in clamping the cutters on the S.125 5 19 0 1¼ ¼ on the teeth of the cutters, or accumulated error on milling machine arbor. Many engineers probably S.150 6 15 0 1½ ¼ the widths of the various collars employed, or perhaps envisage a muscled mechanic wielding a 15 in. spanner a slight distortion on the arbor, a trial cut may reveal and a heavy hammer in his endeavours to tighten up Particulars of the full range of this equipment can an error in one or more positions dependent on the the arbor assembly. In order to dispel any doubts in be obtained from the makers, Euco Tools Ltd., machining limits imposed. Consequently, it becomes this connexion the following formula relating to the 44 London Rd., Kingston-on-Thames, Surrey. series was not justified and accordingly they have been published in the general series of British Standards. British Standard Specifications Price 2.s. each, post free. B.S G.126. Electric Power Metal Rectifiers for Aircraft. Copies of the following specifications may be obtained from the BRITISH STANDARDS Details the requirements for rectifier equipment, INSTITUTION, Sales Department, 24 Victoria Street, London, S.W.1, at the prices indicated rectifier stack assemblies, and rectifier stacks, for rectifying aircraft main and auxiliary A.C. power supplies to D.C. B.S. SP. 22-27: 1950. B.A. Washers for Aircraft rubber, felt and cotton. The standard includes a list Price l.s. Purposes. of hazards and recommends the appropriate types of gloves for each hazard. Requirements are given for B.S. 18: 1950. Tonsile Testing of Metals. British Standards for B.A. washers for aircraft pur materials, sizes, manufactures and methods of test; This is the fourth revision of the standard which was poses have been published by the British Standards recommendations on the storage and preservation of first published in 1904. With the exception of the Institution. These British Standards apply to washers rubber gloves are included, and a note on the inform definition of proof stress, the standard has not been primarily intended for use with screws (2 B.A. and ation to be given when ordering gloves. smaller) used in aircraft instruments, and in electrical fundamentally altered. The definition of proof stress Price 4s. post free. and similar equipment for aircraft. The washers are now adopted is, however, quite different from that identical with those covered by the revision of contained in previous issues, as it has been amended B.S. 57—'B.A. bolts, screws, nuts and washers', now to bring it in line with the practice, current in industry, B.S. 1686.—Long-period high-sensitivity tensile creep in course of preparation, with the exception of pro of obtaining proof stress under load. testing. visions relating to protective treatment and identifi The definition is amplified to indicate methods B.S. 1687.—Medium-sensitivity tensile creep testing. cation. which may be used to ascertain if the material is satis B.S. 1688.—Determination of time to rupture under Price 1s. post free. factory when the actual value of the proof stress is not stress with or without measurement of creep strain. required. Section 1 of the Standard contains the definitions of The increasing use of metals at high temperatures S.B. 1651: 1950.—Industrial Safety Cloves. the principal terms relating to the tensile strength of during recent years has made it essential that satis materials. Section 2 sets out in detail the forms of This standard deals with safety gloves, mittens and factory information should be available about the standard tensile test pieces for sheets, strips, sections, hand-guards for protection against common hazards behaviour of metals at these temperatures. This machined and unmachined rods and bars and so on. in all industries. It is based on practical trials lasting has automatically given rise to a considerable in several years and is designed to canalize the demand It also includes the special test pieces for cast-iron, crease in creep testing, and has in its turn shown the malleable cast iron, steel tubes, cylinders and wire. for safety gloves from more than two hundred different need for standard methods and equipment in order Section 3 deals with the standard methods of proce types now commonly supplied, each type in several that proper comparisons may be made and correct dure for tensile testing, and includes guidance on the sizes, into a range of seventeen preferred types, each interpretations given to the tests made by different preparation of the test piece for testing. supplied in a minimum range of sizes. This standard authorities. ization will facilitate economic production as well as Price 2s. 6d. post free. The standards originated in specifications that had the ordering and stocking of safety gloves. The gloves been prepared specially to meet the needs of the air B.S. G.125: 1950. Turn and Slip Indicators for Aircraft specified arc designed to provide adequate protection, craft industry and it had been originally intended that but also to overcome weak points existing in the past they should be published in the series of British Purposes. and thus to provide the greatest possible economy in Standards for aircraft materials and components; but Covers instruments calibrated for nominal air speeds use. it became clear that the field of application was so of 140 and 280 knots. The gloves fall into five groups: leather, plastics, wide that the restriction of the standards to this Price 1s. post free. May 1951
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: May 1, 1951
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