| 摘要 |
A drawing compass has mounted on a projecting stub an internally screw-threaded clamping nut which is for clamping a pencil, ball-point pen, or the like in place in the stub. The nut is held captive on an external screw thread on the stub by stop means at the inner and outer ends of the external screw thread. The clamping nut is composed of plastics material sufficiently resilient to permit the nut, during assembly of the compass, to be moved past one of the stop means at an end of the external screw thread and sprung into operative engagement with the said thread. The stub may be die-cast and have an unthreaded outer portion having an inner end which is adjacent to the outer end of the external screw thread. The inner end constitutes the stop means for the clamping nut at outer end of said thread. The stub also has an unthreaded inner portion having an outer end which is adjacent to the inner end of the external screw thread. The outer end constitutes the stop means for the nut at the inner end of said thread. |
