CKISER: I cannot help too much because I have seen very few circular keys. There are other issues besides strength. Key design is limited by codes and standards. ASME and SAE may have some key standards. To my way of thinking if the diameter is the same as the side length the load carrying capability may be same. There are other issues such as width and depth of the key slot, stress concnetrations and others. If possible, I would stay with a rectangular key.
Is it a tapered pin? If so, it can be driven in tight and may not require secondary (setscrew or equivalent) locking means. I would expect such an arangement to be machined in place resulting in a matched assembly.
I think he's referring to a 'Dutch pin', where a smooth bore gear, cam, etc., is lightly pressed over a smooth hub, a small hole is drilled parallel to the shaft axis at the interface radius, and a round pin is driven into the hole and peened at both ends or trapped by adjacent components. I've seen it done a few times with taper pins, peened at the small end.
It requires axial access to at least one end of the hub/gear interface after they are assembled. I've never, ever seen it done on the separate parts, e.g. mill a half- round keyway in both hub and gear separately, and set up the tolerances on hub, gear and pin so it can be assembled and isn't loose.
I've never seen a standard for it. It's a simple quick way to key a >particular< pair of parts together without broaching or milling. It's basically impossible to do it with interchangeable parts, and I can't think of a reason why anyone would try.
It's not as strong as an equivalent Kennedy key (square key installed diagonally), for which there are standards, except to the extent that the outside corner of the Kennedy keyway would be a stress raiser.
Well, hold on a sec. I have seen a partially derivative assembly, a motorcycle disc brake assembly with six or eight half- holes in a flange on the aluminum hub and the inner radius of an iron brake disc, retained to each other >loosely< by short double- flanged cylinders. The assembly was clearly designed to allow the disc and the hub to move (and expand) independently of each other to allow for thermal expansion and 'float' of the brake disc. And to look 'zoomy'.
Stick to standard stuff unless that's impossible.
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
After my original post, I did a little search on the net and found two sites (below) with some info on what I am referring to, but could not find any info on standards.
