634,361. Screw thread grinding machines. DALZEN, W. F. April 20, 1942, No. 5238. Convention date, April 19, 1941. [Class 60] A thread grinding machine comprises a carriage support disposed upon a base, a longitudinally reciprocable carriage slidably mounted upon said support with a spindle thereon for rotatably supporting a work-piece, a rotatable grinding wheel adjustably supported adjacent said work-piece, a drive shaft, a cam operable from said drive shaft, a lever pivoted on one end to said carriage support and co-operatively engaging said cam on its other end, and a fulcrum intermediate the ends of said lever whereby an intermittent radial motion of said carriage support relative to said grinding wheel is imparted. The grinding wheel 20 belt-driven from step pulleys on a motor 36 is mounted in a housing 14 vertically adjustable on a column 19 which is angularly adjustable, about a vertical axis, on a slide longitudinally adjustable on the base 28. The work is supported by a centre 76<SP>11</SP> and by a tailstock 78 adjustable towards and away from the centre, and also vertically adjustable for grinding taper work. The work is rotated by a spindle 76. The work carriage 68 is mounted, by ball bearings 82, for reciprocation by lead screw 74, on an inclined carriage support 81 which can rock on the base 28. A motor 39 drives, through step pulleys 40, belt 41, step pulleys 42, pulley 44, belt 45 and pulley 44<SP>1</SP>, a sleeve 46 which through gears 50, 55, 57, 52 drives a shaft 48 ; the gear 52 is splined on the shaft 48 and can be moved axially, by fork 58 operated by handle 59, so that clutch parts 54 thereon engage clutch parts 51 on the gear 50 so as to give a direct drive. The shaft 48 drives, through reversing gear 60, 61, 63, a shaft 62. The reversible shaft 62 drives, through gears 72, 73 the lead screw 74, the other end of which is supported by a centre 150. The reversible shaft 62 also drives, through gears 72, 73, 74<SP>1</SP> the work spindle 76 ; the gear 74<SP>1</SP> which is splined on the work spindle 76 to allow for the axial traverse of the work carriage, can be moved axially by means of fork 74<SP>11</SP>, so that it meshes with an idle gear 73<SP>1</SP> in mesh with gear 73, thus reversing the direction of rotation of the work relative to the direction of rotation of the lead screw. The clutch part 64 of the reversing gear 60, 61, 63 is movable on the shaft 62 to determine the direction of rotation ; movement is effected by a handle 65 which rotates a shaft 66 and thus through bevel gears 67, 68<SP>1</SP> a gear 70 engaging a rack 71 on a shift fork. For automatic reversal of the work carriage, a roller 66<SP>1</SP> on the handle 65 is contacted by adjustable dogs on the work table. The shaft 62 also drives, through gears 87, 88 a cam-shaft 89 bearing a cam 90 which acts on one end of a lever 80 which at its other end 83 is connected to the carriage support 81 ; an adjustable fulcrum 91 is provided. The carriage support 81 is pivoted about the drive shaft 62, and by the action of the cam 90 is rocked to give radial relief when grinding taps, reamers, &c. A follower 96 on the work carriage 68 contacts the top of a longitudinally disposed rail 93 having a ramp 95 at its end, whereby at the end of a traverse the work is rocked away from the grinding wheel ; this provides " run-out " of the thread channel, to eliminate abrupt stoppage of the thread. The rail 93 may be inclined so as to grind taper work ; the upper surface of the rail may be shaped so as to impart a desired shape to the work. For these operations the cam 90 is rendered inoperative. A tray 31 is provided to catch coolant, which is supplied to the grinding wheel and work by a centrifugal pump 33 in the sump 32 ; a splash guard 34 is secured by clips 35. Trueing grinding wheel.-For trueing the flanks of the grinding wheel, a wheel dresser A is provided. The dresser is mounted in a housing 11 vertically movable, with interposed balls, relative to support 12 secured to the grinding wheel housing 14. The latter is vertically adjustable on the column 19 by means of hand wheel 15, acting through gears 16, 17 and screw 18. The housing 11 is secured at 22 to one end by a lever 21 pivoted at its centre 23 to the grinding wheel housing 14, the other end of the lever being connected at 19<SP>1</SP> to the column 19 ; the connection 19<SP>1</SP> is adjustable by means of a screwed shaft 21<SP>1</SP>. The housing 11 has members 97, 98 pivoted thereto at 120 and angularly adjustable by screws 146. On the members 97, 98 are mounted shafts carrying diamond mountings 107 which are reciprocated by means of a lever 108. To produce a curved edge on the grinding wheel an auxiliary dresser B is provided ; this comprises a diamond mounting 141 carried by member 139<SP>1</SP> which can be rotated by a handle 140 ; the member 139<SP>1</SP> is mounted by means of screw-adjusted compound slides 137, 131 on a base 127 secured to the housing 11.