Combination spanners, also known as combi spanners, are hand tools used for tightening and loosening nuts or bolt heads with a hexagonal shape. They are typically made from hardened chrome vanadium steel or beryllium copper and typically comprise of a ring on one end and an open jaw on the other.
The ring end recess is generally a six-point or twelve-point opening and sometimes offers a ratchet mechanism that helps apply maximum force with minimal user effort. Combination wrenches are available in most metric (mm) and imperial (inch) sizes to allow for greater functionality across a wider range of applications.
Imperial spanners use the AF (Across Flats) system, where the measurement is taken between two parallel sides of the fastener. An inch spanner will fit an inch fastener.
Metric refers to the size of the thread rather than the size of the head of the fastener. Common sizes include M6, M8, M10 and M12. The ’M’ prefix is short for metric while the number indicates the width of the threaded section. For example, while there can be a few variations in millimetres, you would normally see a 10 mm spanner being used for an M6 fastener.
Combi spanners are used by: