A Monthly Selection of Recent Equipment and New Methods tested is first mounted between the centres and A Universal Worm Gear Tester checked for concentricity by means of a clock The universal worm gear testing machine indicator mounted on ball carriages at right made by the David Brown Tool Co. provides an angles to each other, which is attached to the accurate yet rapid means of checking all dimen auxiliary slide and is adjustable to suit the dia sions upon which the performanc e and inter- meter of the worm under test. The base carrying changeability of a worm depends, and for test the ball carriage can be slid along the bed and ing finished wheels in conjunction with a maste r locked in any position. A spring plunger form worm, thus providing a rapid check to be made ing part of the indicator contacts the worm, on the accuracy of th e tooth contact. It provides which is rotated by hand, when any error in con a convenient means of meshing together indi centricity will be shown on the dial. Th e latter is vidual pairs of worm gear for the purpose of graduated to 0.001 in. or 0.01 mm. as required. these tests where the quantities involved do not Thread Thickness: For checking the thick adapter being determined by means of a micro warrant the expense of a master worm. ness of the worm thread, a steel ball of selected meter straight-edge, the lower surface of which Its efficiency is further increased by the pro diameter attached to a ball carriage is inserted is placed on the top surface of the adapter and vision of an auxiliary slide which will accommo in the space between two adjacent threads of a the micrometer head adjusted to touch a bar of date the various worm testing instruments, all master worm. The dial of the indicator is then known diameter mounted between the adjust of which can be adapte d without disturbing the set to zero. By replacing the master worm with able centres. Any error in the position of the headstock centres on the main bed. the worm to be tested and inserting the ball adapter can be corrected through the micro The machine checks: concentricity of the gauge between each pair of threads , a compari meter elevating nut. The wheel carriage is then worm, thickness of worm thread, pressure angle son on the thread thickness may be obtained moved towards the worm by rotatio n of one or of worm thread, pitch and indexing of worm other of the operating handwheels until the threads, thickness of wor m wheel teeth and con gears are meshing at the correct centre distance. tact area on the worm wheel teeth. Red lead or prussian blue is then smeared over The bed embodies three horizontal slideways, the worm thread and the gears rotated by hand, two of which are parallel to each other and the when the distribution of contac t can be observed third at right angles to them. The main slide by the markings on the wheel teeth. carries a pair of headstock centres for support Standard Equipment—Supplied with the Machine ing the worm, and the one at right angles to it Micrometer bar for setting height of wormwheel datum face. bears an adjustable arbor adapter on which th e Ball carriage clock indicator. Worm wheel thickness comparator with micrometer adjustment. worm wheel is mounted . The bed, supported by One standard headstock. three-point suspensions, is securely bolted to a One headstock with dividing mechanism. Three worm wheel arbors 1 in.—l ½ in . and 2 in. diameter. rigid welded steel cabinet of box section which provides ample cupboard accommodation for Special Equipment the accessories. One headstock centre had hand One sine bar pressure angle checking instrument. wheels for fine adjustment. The headstocks Capacity and Sizes themselves can be locked on the slide in any Max. centre distance 300 mm. 12 in. Max. dia. of worm 150 mm. 6 in. position to suit the length and design of worm- Max. length of wormshaft 760 mm. 2 ft. 6 in. shaft. Floor space l·2 m. x 0·9 m. 4 ft. x 3 ft. Complete details can be had on application to the David Brown The slide which carries the worm wheel arbor Tool Co., Park Works, Huddersfield. is controlled by a traverse screw passing right across the bed of the machine, the screw being provided with two operating hand-wheels, one at either end, each having a graduated dial BRITISH STANDARD SPECIFICATIONS from the plus or minus readings on the dial. In which, in conjunction with a vernier scale, en 'Copies of the following Specifications can be obtained at the price a worm of normal design, variation in thickness ables the setting to be measured to 0.001 in. o r indicated, from TH E BRITISH STANDARDS INSTITUTION, 28 Victoria is multiplied on the indicator by reason of the Street, London, S.W.I . 0.01 mm. inclination of the sides of the thread. The indi A micrometer sleeve—screwed on its outside B.S. 1392.—Terms and Definitions Relating to Heat cator may be moved along the machine bed and diameter—is fitted into the slide so that it is free Treatment of Steel. a further series of similar measurements taken. to move in a vertical direction, but is prevented This British Standard includes a list of terms in Where the scale of productio n does not justify by a sliding key from rotating. Vertical adjust general use throughout the steel industries relating a master worm, the initial check on the tooth to the heat treatment of steel, and the definitions ment of approximately 1 in. is effected by rota thickness is by means of a gear tooth caliper. of these terms are specified. An appendix gives fur tion of a hand-wheel integral with a steel nut , Pressure Angle or Profile: For extreme accu ther details of the transformation ranges. which engages the screwed portion of the arbor racy in the measurement of the pressure angle, Price 2s. post free. sleeve. By means of a graduated dial, the setting a special fixture can be supplied by which th e can be measured to 0.001 in. or 0.01 mm. B.S. No. 1420.—Glossary of Terms Applicable to pressure angle is checked with a stylus passing Concentricity of Worm: The worm to be Wrought Products in Copper, Zinc, Brass, and other down the flanks of the thread on a slide that is Copper Alloys. set to the correct angle by the sine bar method, This glossary is based on proposals submitted by the and registers any errors on a clock indicator. British Non-ferrous Metals Federation which had Thickness of Worm Wheel Teeth: For testing taken steps to obtain representative views from the trade interests concerned. the thickness of the wheel teeth, a double ball The definitions have been related throughout to cur micrometer is provided. This instrument com rent commercial practice and due consideration has prises a straight-edge carrying two adjustable been given to Customs' definitions. These factors have arms. Spherical balls are mounted on the ex necessitated the omission of certain terms and the tremities of these arms, one ball being rigidly drafting of several of the definitions in a manner less secured to its arm and the other being mounted precise than is usual in British Standards. on a pivoted holder provided with a micrometer The scope of the glossary has been limited to adjustment. The instrument is set in the first wrought products, but it is hoped that further sections place to a master worm wheel, and all others t o will be published in due course covering raw mater- rials, cast shapes and, possibly, certain fabricated pro the same specification are made to give the same ducts. Although the terms have been defined in rela reading so that, so far as tooth thickness is con tion to copper alloys and zinc, it is appreciated that the cerned, all will mesh similarly with an accurate issue of the glossary as a British Standard will have an worm. indirect effect on the terminology used for other Contact Area: In testing the wheel for con metals and alloys. The Institution will appreciate any tact, the wheel is mounted on the worm wheel comments on the possible extension of the scope of the arbor by means of a suitable adapter and glossary or on the publication of separate sections to cover terms used in relation to other non-ferrous brought in exact horizontal alignment with th e metals. Price 25. post free. axis of a master worm, the height of the work March 1948
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Mar 1, 1948
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