Combination Spanner (9mm)

That is not an oversight by Harden so much as a reflection of how sets are built: they carry the sizes used most and leave the rest to be bought individually. It does mean a workshop working through a set will jump straight from 8 to 10, and sooner or later meet a 9mm head with neither one fitting.

What happens next is the reason this page exists. Faced with a 9mm nut and no 9mm spanner, a great many people reach for the 10. It goes on. It feels only slightly loose. And it is loose in exactly the way that destroys fasteners, because a spanner one size too large no longer bears on the flats of the nut at all. It touches only the six corners, so the whole load is carried on six narrow lines of metal instead of across the faces. Under any real effort those corners deform, the nut becomes progressively rounder, and each attempt after that has less to grip than the last. A nut that was merely tight is now a nut that needs cutting off.

That is the argument for owning the odd sizes. A single spanner costs a fraction of the time lost to one rounded fastener in an awkward place.

Nine millimetre heads are found on small machinery and engine fixings, on some Japanese vehicle ancillaries, on appliance and equipment assemblies, on electrical gear and on light fabrication work.

It is forged carbon steel, hardened and tempered, with satin matt chrome plating to keep the monsoon off it.

Buyers are vehicle and motorcycle technicians, machinery fitters, appliance and equipment repairers, electricians, and hardware shops that stock the in between sizes because their customers keep asking.

If you are unsure whether the fastener in front of you is 9 or 10mm, bring it in or send us a photograph on 94 77 111 8880. We would rather identify it than have you round it off. Island-wide delivery.