Whitworth Thread Root Angle?

[Arnak]

Hi Folks,

I am attempting to grind a threading tool to the correct root radius for a Whitworth thread of 2.25" dia x 8 tpi.

Could someone explain how to calculate the root angle and depth of thread please?:noidea:

Thanks,

Arnak

 

[Tin Falcon]

Look here page 10
http://www.gerardsgarage.com/supportfiles/Threading_Tables.pdf

root radius is .1373P or .1373 x.125= .017
D = .6403P .6403 x.125=.080
Tin

 

[Arnak]

Hi Tin,

Thanks very much for that.

Printed and saved.

Arnak

 

[compspecial]

And thread angle is 55degrees.
Stew

 

[Arnak]

Hi Stew,

Got that thanks very much.

Arnak

 

[modelman1838]

Does anyone know why Whitworth chose 55 degrees, he must have had good reason or he would have used 60 degrees.

Hugh