Square nut to hex calculation

[NickRobinson]

On the boat in a rainy Fleetwood (all well BTW)
The Yanmar 2QM's anodes lurk behind 21mm across the flats square plugs (My new Aldi digi calipers tell me)

I've had them out before, shifters and stillsons. However, who's bored enough to give me the appropriate hex/bihex socket size?

 

[jdc]

The square is 21mm, and I assume you want to fit on a socket with 12 'notches', and then translate to the nearest hex AF size.

In which case:
Let the square's AF be 'a'
The 1/2 digonal of the sqaure will be a/sqrt(2).

For it to fit on a 12 pointed socket the socket must also have 1/2 diagonal = a/sqrt(2)

The width across flats of a hexagon is sqrt(3)/2 times the diagonal, so

The equiavalent hexagonal AF should be 2 x a / sqrt(2) x sqrt(3) / 2 = a * sqrt(3/2)
= 21 x 1.225 = 25.7mm.

This is just greater than 1" (25.4mm) and just less than 26mm (Qu. is there a 26mm AF metric spanner?).

You best check this!

PS: 9/16 Whitworth is 25.65mm AF

 

[colhel]

For a hex multiply the a/f by 1.1547 to give across the corners. If a square multiply the a/f by 1.4142 to give across the corners.

 

[jdc]

For a hex multiply the a/f by 1.1547 to give across the corners. If a square multiply the a/f by 1.4142 to give across the corners.

Good: your numbers are the same as I just worked out (sqrt(2) = 1.4142 and 2/sqrt(3) = 1.1547).

 

[colhel]

I'm just a simple machinist, I wrote the numbers on the back of my Zeus book about 30 years ago and never forgot them
But think of a hex as 60 degrees and a square as 45 degrees

 

[NickRobinson]

Thanks, folks...
If my socket set was here or my square nut was at home.... :encouragement: