Marking device for stair tread fixing - has bit which centres in ferrule with point projecting upward to mark spindle location on tread

摘要

The self-centring punch-bit (1) is for use in fixing a timber stair-tread (5) with spindle and ferrule (8). The bit comprises a solid cylindrical base (2) with a sharp conical head (4) and intermediate circumferential flange (3). A bit is placed in each ferrule (7) with the base entring the ferrule, the flange limiting penetration and the point (4) projecting upwards. The tread is then accurately positioned and pressed onto the points. The location (14) of the screw-spindles is, thus accurately defined. A spindle is finally screwed in at each point (14), the bits (1) removed, and the tread (5) installed with spindles penetrating ferrules.