GB1355025A - Cutting-head for internal screw-threads - Google Patents

Abstract

1355025 Cutting internal screw threads H W KRAUSS [trading as H WILLY KRAUSS] 2 Feb 1973 [4 Feb 1972] 5364/73 Heading B3N A cutting head 1 for forming an internal screw thread comprises a body 3 having a plurality of axially extending grooves with cutting elements 4 mounted for axial and radial movement therein, each said groove being provided at its bottom with a plurality of surfaces inclined to the axis of the body and each cutting element being provided with a plurality of similar surfaces, whereby upon axial movement of the cutting element in said grooves coaction of the cutting element surfaces and the groove surfaces will cause radial movement of the cutting elements. Preferably the surfaces are sawtooth-shape with the two sections of each tooth having different angular slopes sections 8 and 12 being approximately 45 degreees whilst sections 9 and 13 are approximately 5 degrees. The rear of each element has a projection 17 that engages in a groove 19 in a switch-over ring 20. The ring is movable by a switch lever 30 to position the elements in an operative position as shown in Fig. 2. A stop 35 controls the movement of the elements and thus allows for adjustment of the diameter of the threads to be produced. In operation, at the end of an operative stroke the body 3 of the head is stopped and the elements are pulled forward by a rotating workpiece so that the sawtooth shapes align and the elements are moved radially inward by springs 22 and annular spring 28.