GB402966A - Improvements in or relating to abrasive grinding or milling machines by which a toolis traversed over a workpiece in a helical path - Google Patents

Abstract

402,966. Grinding or milling helical grooves &c. TENNANT, W. J., 111, Hatton Garden, London.-(Aktiebolaget Svenska Kullagerfabrieken ; 17, Artillerigatan Gothenburg, Sweden.) March 2, 1933, No. 6431. [Class 60.] A grinding or milling machine in which the tool is traversed over a work piece in a helical path, for example in sharpening a spirally spirally fluted tap, comprises a base 1 having a vertically adjustable table 2 carrying a cross slide and a longitudinally slidable work-carriage 11 movable by hand-wheels 4, 5 respectively. The work 6 is supported by centres 7, 8, and during the traverse of the carriage is rotated by an amount corresponding to the twist of the flute, so that the grinding-wheel 12, which rotates only, contacts all along the flute. The rotation of the work is produced by a guide bar 13, of channel section, adjustably pivoted to the table 2 at 14 and serving to guide a roller carried by a double rack 16, either set of teeth of which, according to the hand of the helix, may be brought into gear with a pinion 17, which may be clamped to a shaft 18 by means of a screw 124. The shaft 18 drives, through bevel gears 19, 20, a sleeve 21, within which is rotatably mounted a hollow shaft 34, which receives the centre 8 and can be locked to the sleeve 21 through an index-plate 25 secured to the sleeve and an arm 27 adjustably secured to the shaft 34 and carrying a pin which may engage holes in the index plate. In order to set the bar 13, the pitch of the helical groove is ascertained by means of a scale 36 on the index-plate, on which is read the amount of rotation imparted to the work whilst it is moved a definite axial distance as determined by dogs 38, 39 on the carriage 11, the dogs being set the required distance apart, for example 50, 100 or 200 millimetres, by parts 43-45 on a gauge bar 41 and engaging a fixed stop 37 on the carriage 2. The bar 13 is then set by means of scales, corresponding to the axial movement of the work, on a part 33, to an inclination corresponding to the pitch as thus ascertained.