Meaning of Numerology on spanners and wrenches

When I see any spanner then always there is a number on its ends, like 10,11,12...
What is the exact meaning of that numbers?

Questions by kamlesh431   answers by kamlesh431

Showing Answers 1 - 8 of 8 Answers


  • Jul 23rd, 2014

this number is used because it is show that, which size of bolt or nut is opened by this spanner or in other words the number is show that only this size of nut or bolt is tight and open by it.

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  • Nov 14th, 2014

It indicates the OD(outer diameter) of nuts and bolts by which they can be tightened or loosened

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Anand Kher

  • Dec 28th, 2014

The number denotes the width across flat of the nut/opening of the spanner (size in mm/inch used for)

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  • Jan 5th, 2015

Its called Across Flat dimension (A/F). When you see nut or bolt head, it has a hexagonal feature. Which means two opposite parallel faces (total of 6 sides )and the distance between the two opposite face is the number that you are seeing in the Spanner. for example; if a spanner number is 10 in size, it is used to tighten / loosen any part which has two opposite parallel face with 10mm (normally tolerance of spanner will be more in plus side) apart.
Thanks in advance

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  • Jan 21st, 2015

Its the Jaw size of the spanner.

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Surendra Nath Singh

  • Mar 4th, 2018

The number given on spanner is outer diameter of Nut and bolt in MM.

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