| 摘要 |
<p>A thread forming screw is formed from a blank having a cylindrical shank and a tapered conical end. helical screw thread is formed on the shank and a tapered lead-in section is provided at one end of the screw for forming a thread in a workpiece. The lead-in section includes a plurality of spaced lobes each having outer convex surfaces and they collectively define a thread forming section on the tapered end of the screw. Concave surfaces formed in the tapered end extend between and space the lobes circumferential and provide substantial concavities between the lobes to reduce friction and turning torque when forming threads in a workups. Curved ramp surfaces join each of the concavities and each of the lobes to eliminate sharp interfaces between the lobes and the concavities.</p> |
