Spanner Jaw Sizes by Member R. Nick Taylor

Spanner Jaw Sizes 

by Member R. Nick Taylor

Since I had to stop driving for 4 weeks, I thought that the time could be usefully spent sorting out my spanners! 

I must have 60 Open Ended plus some with Custom Made.  

My own I can measure and relate to metric, A/F fraction and British.  

Then cross reference to published tables.

It turned out to be a bigger job than when I was developing the Aluminium Tool Tray. 

However, I have now come up with three tables listed lower down this report.  

British Standard Whitworth Screw Threads {BSW}  (Bolt Diameter, Thread Form and Pitch and Hexagon size) 

Size was related to bolt diameter and specified in inches & fractions.  The 'spanner across flats' 

gap must be larger than BSW or British Standard Fine {BSF} bolt size.  

Material saving needs resulted in a reduction in Hexagon to next lower size

Hexagon Nuts & Bolts compared to Spanner Markings - Nick’s Crib ranking by size

·       Three Conventions for Nuts/Bolts are Metric, American and British. 

·       Metric (M) and American (AF) nuts are sized as the 'Measurement Across the Nut Flats so Spanners are  marked/stamped.  

This means 10M Spanner will fit a 10M Across the Flats Metric Nut.  

Equally, A ½”AF spanner will fit will fit a ½” Across the Flats Nut.

·       British nuts/bolts BSW and BSF are sized by bolt diameter.  

Open ended British spanners traditionally had the next size down at the free end.  

So for material saving (and stronger materials) Hexagon moved one size down. 

Manufacturing specification had to change. Old spanners and markings remained.  

Hence my crib sheet to insert British Spanners into the correct place. 

·       Sizes are nominally.  Nut/Bolt Across the Flats dimension in mm. and inches and will be to manufacturers specification.  

Spanner Jaw Gaps are based on approx measurement of my open ended.  

The Plating of Nuts can cause clearance problems

·       Socket, Ring, Box Spanners of same size marking should fit in place of Open Ended Spanners.

·       Eg Typical Small Sizes 3.2M to 9M

·       Eg Typical Medium Sizes 10M to 20M

·       Eg Typical Large Sizes 21M and above

Conclusion.  

Always Measure Nut Across Flats and from my Tables Below and Select the Spanner with nearest Jaw Size.  

This gives you the correct size for Ring, Box, Socket or Open Ended Spanner.

These three sheets are useful to me to put in my tool roll, so that I can measure the Nut and then home in on the Correct Size of Open Ended , Ring, Socket, etc, rather than that usual random lucky dip method I've used for years.

I am thinking of putting two tables front and back on visiting card or postcard size. 

Depending if legible.  

If tables have no gross error and format looks ok I could photo and resize get put on disc for local printer to reproduce.  

Any way an idea.

Best Regards

Nick

I hope that you find this topic useful

Frank