Divider Drafting Compass, Small, Heavy Metal

Divider Drafting Compass, Small, Heavy Metal.

A compass draws a circle of a set radius and — if it is any good — holds that radius all the way round.

A joint that slips by half a millimetre turns a circle into a spiral, which on a technical drawing means the line does not meet itself. Set the radius against a ruler rather than by eye, sharpen the lead to a chisel rather than a point, and lean the compass slightly in the direction of travel.

• Set the radius against a ruler, not by eye
• Sharpen the lead to a chisel for a constant-width arc
• A slipping joint gives a spiral, not a circle