On 19 May 2024 at 10:16 Ian Hewson Said:

Hi Dalboy

If it’s for the flywheels on your Farm Boy, try Arc’s metric broach’s and make your own guide up for the imperial shaft. Worked well on mine.

Usefull guide to broaching on the site also.

Ian

Yes it is for the Farm Boy I have already cut the keyway on the crank to 1/8″. I have been out of the workshop due unforeseen circumstances but hope to be back on it very soon.

On 19 May 2024 at 10:22 JasonB Said:

The class letter refers to the width of the “spine” so an 1/8″ Type A will have a 1/8″ spine and fit into bushes with a 1/8″ slot.

Type B at 1/8″ will have a 3/16″ spline and fit into a 3/16″ slotted bush.

If you are generally going to be making models of this sort of size then I would go with type A as that allows for smaller bushes and therefore smaller shafts so you can do 1/16″ and 3/32″ keyways as well as 1/8″ all with the same bush Which should cover you for shafts from 1/4″ dia to 1/2″

Thank you Jason sounds like a good explanation and suggesstion to which one to go for.