| 摘要 |
A pair of compasses has a leg provided with a lower portion 1b having a hole 1c for receiving a pencil. Lower portion 1b carries an axially rotatable plastics clamping ring 2 provided with a cam surface (2a) which moves axially across hole 1c on rotation as it rides on and cooperates with a two part helical cam surface (5) on an end stop 7. A pencil can be clamped in the hole 1c by a wedging action of the ring 2 in between the cam surface (5) and the pencil. <IMAGE> |
