Patent GB-568534-A (GB)
Title: Improvements in or relating to tap reconditioning machines
IPC: B24B3/18
Filed: 1943-01-09
Abstract: 568,534. Grinding 'taps. DETROIT TAP & TOOL CO. Jan. 9, 1943, No. 452. Convention date, May 20, 1942. [Class 60] In a tap reconditioning machine the tap is first mounted in a chuck which is arranged at a predetermined angle relatively to a cylindrical abrasive wheel and is rotatable about an axis parallel to, but offset from, its own axis to enable the surfaces of the lands between adjacent flutes to be ground to the required chamfer, and is subsequently mounted in a second chuck carried by an arm pivoted on an axis parallel to the axis of a frusto-conical abrasive wheel to enable the tapered portions of the flutes to be ground. The machine shown comprises abrasive wheels 20, 91 carried by an electric motor 12 which is adjustable by a screw 16 along ways 15 on a base 10 and is locked in the adjusted position by a screw 19. The chuck 52 in which the tap is first mounted, is carried by a housing 50 which is pivoted by a screw 56 to a bushing 46 and may be secured with its axis eccentric to the bushing by a screw 57. The bushing 46 is rotatable in a sleeve 45 in a support 35 which is adjustably secured by a hand nut 36 to a flanged bracket 32 pivotally adjustable on the base 10. The movement of the bushing 46 is effected by a handle 75 pivoted to a radial boss 67 on the housing 50 and is limited by the engagement of a screw 87 inserted in one of a series of holes 86 in the support 35 and a stop pin 85 on the support with gapped collar 18 on the bushing. When swung about its pivot pin 76 the handle 75 withdraws a spring-pressed plunger 69 from a notched index-drum keyed to the shank 65 of the chuck 52 and allows the chuck to be turned for the grinding of the next land. The position in which the tap is initially secured in the chuck is indicated by the engagement of a finger 174 carried by a pivoted locating arm 173 with a flute on the tap. The abrasive wheel 20 is partly surrounded by a housing 21 fitted with a removable cover-plate 24 and formed with two cylindrical bosses 22, 23. The wheel may be trued by a diamond pointed screw 29 carried by an arm 26 having a pin 27 inserted in an axial bore 28 in the boss 22. When not in use, the pin 27 is inserted in an axial bore in the boss 23. After the land grinding operation, the tap is secured in a chuck 137 for the " spiral pointing " or grinding of the flutes by the abrasive wheel 91. The chuck 137 is mounted in a housing 136 bolted to a bracket 131 which is angularly adjustable about a bolt 132 on a member 119 slidably mounted in a housing 110 anchored to a pin 97. The pin 97 is journalled in walls 95, 96 on the base 10 and may be adjusted axially by a crank 102 on a screw 101 passing through a nut 99 and connected to the pin 97 through a ball bearing 103. The member 119 is adjusted on guide pins 117, 118 secured to the housing 110 by a screw 112 formed with a handle 113 by which the tap is brought into engagement with the wheel 91 against the resistance of a torsion spring 105 engaging the pin 97. The movement of the tap is limited by a stop pin 150. The chuck 137 may be rotated manually in the housing 136 by a handle 145 for the grinding of the next flute' on the lifting of a spring-pressed lug 140 engaging a peripherally notched index disc 139. ' Grinding wheel marks on the flute may be removed by holding the tap against a small diameter pencil grinding wheel driven by an electric motor housed within the base 10.