GB562534A - Improvements in the machining of thread-rolling dies - Google Patents

Abstract

562,534. Grinding screw threads. HERBERT, Ltd., A., and TURNBULL, D. G. March 25, 1943, No. 4839. [Class 60] [Also in Group XXII] In a process and apparatus for chamfering the ends of a screw-thread rolling die 24, Figs. 4 and 5, as at 27, the thread-forming grooves and ridges 25 are first cut by a milling or grinding tool and the die is then tilted in two directions relatively to the cutter so that the chamfered grooves 27 may be cut with the'line 27a at the inner end of the chamfer at right angles to the longitudinal faces 26 of the die. The die is clamped by a plate 31 and screws 30 in a holder 16 carried by a base 12, the die being mounted in a support 29 in the holder having an inclined lower surface 29a so that the base 12 may be tilted transversely by a wedge 14 whilst the upper surface of the die remains horizontal in the transverse direction. For cutting the grooves 25 the holder 16 is supported in the base 12 in a parallel sided packing piece 17, Fig. 3, with the upper side of the die in a horizontal plane in the longitudinal direction as well as the transverse direction. After machining of the grooves 25, by a cutter inclined to the edges 26 at the thread angle 28, a gauge 35, consisting of a cylindrical rod cut away on a diametrical plane, is secured to the die with its axis along the required line 27a and an indicator 37 is adjusted to make contact with the gauge whilst giving a zero reading. A screw 36 on the base is also adjusted to contact the gauge 35 in the longitudinal direction. The screws 21 securing the holder 16 to the base are then loosened and the packing piece 17 replaced by a wedge 38, Fig. 2, having the same angle as the chamfer required which is adjusted until the indicator 37 is again in contact with the gauge 35 and giving zero reading, thus ensuring that the line 27a occupies the same position as before and effecting a tilting of the die about this line in a plane parallel to the inclined face 13 of the base 12. The screws 21 may then be tightened, the gauge 35 and indicator 37 removed, and the chamfered grooves 27 machined in line with the grooves 25. For chamfering the other end of the die, the wedge 38 is reversed and the gauge and indicator applied to that end of the die. The longitudinal position of the packing pieces 17 is determined by a screw 18, Fig. 1 (not shown), in the base 12 and that of the die 24 by a screw 34. The angle of tilt imparted by the wedge 14 is between 3 and 6 minutes.