Die size to clean up threads on drive side of crankshaft

[Dmftoy1]

68 750 commando

What die do not need to order to clean up the threads?

By my measurement the thread pitch gauge says 20g 1/4

Using a caliper in inches the top of threads seem to be .619
The bottom of threads seems to be .588

I've been over all the charts at british fasteners.com and I'll be damned if I can find it in BSF, cei or unf. .

HELP!

 

[L.A.B.]

5/8 - 20 tpi Cycle.

http://www.motalia.co.uk/Html/Charts/cycle_chart.html

 

[Dmftoy1]

Found it - 5/8 x 20 bsC - parts book and oldbritts site was the key