| 摘要 |
1284951 Self-tapping screws BOLLHOFF & CO 5 May 1970 [20 May 1969] 21611/70 Heading B3N [Also in Division F2] A self-tapping self-locking screwthreaded member 1 or insert for cutting a thread in a workpiece of soft material, the cutting thread of the member has a pitch angleγand a friction angle p which is determined by the friction member Á when cutting is performed, the thread has two flanks 4, 15 which make angles # 1 , # 2 with a plane normal to the axis of the member, # 1 is selected such that # 2 is selected such that wherein the pitch angleγis greater than the friction angle p. This means that the member needs an end load only on face 6 to rotate the member into engagement with a workpiece and, that once in position a tensioning load will not cause the member to undo itself. The thread may be a multiple thread or a differential thread where the pitch angle decreases toward the outer end. The member may have an internal thread 16 or an outer end portion may be threaded or knurled 19. At the inner end the member may have a non-threaded portion 18 and a slot 17.
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