What are the advantages and disadvantages of using circular section ("Scotch") keys, keyseats and keyways? I am not referring to Woodruff style, I am only interested in the type where the key itself if a full cylindrical piece and the shear force is diametric. For instance...
Woodruff style and straight cut style seem overwhelmingly more common than circular section types. What is the reason for this?
It seems to me that it would be very convenient to be able to simply drill a keyway/keyseat into a parts before turning the ID/OD to it's final diameter.
In addition I would think that a circular feature such as this would eliminate stress concentrations that would be present on broached and milled square section cuts. Key joint cutting is in any case a precision operation so I doubt there's any major loss in tolerance quality over other types of keys.
I don't have any particular application in mind for this, I'm merely curious. However I would like to know some situations where circular keys are advantageous or not.
Edit: Further thoughts: Wouldn't a circular key actually experience more of a compression force than a shear force, especially under high torque applications? Given the many non-parallel shear forces all converging at the centre of the key, this would manifest as compression would it not?