Setscrews and Keyways

90 degree or 180 degree from what reference??? I always thought the set screw was usually directly over the key and keyway, so the setscrew would not damage the shaft. In this case the setscrew digs into the key. I have also seen applications where keyways are 120 degrees apart, rather than 90 or 180 degrees apart.

Set screw should be directly over the key. This gives the best results by preventing the key getting damaged due to sudden/ shock loads and helps the key stay in position.

It seems to me that 180 would be a problem if there were any mis-fit in the key. Above the key would put the most pressure on coincident inner and outer curves of the two components and seem to ensure better concentricity.

1 on the key, 1 @ 90degrees. the set screw on the key won't keep the parts from falling apart, if you have loose fits, large side loads. The addition of a shallow nest on the shaft will keep things located. Use taper locks [no set screws touching key or shaft] to minimumize runout [ lack of concentricity ] Garth

Machinery's Handbook (20th edition) has no description of the application of setscrews to keys. However there is a table of setscrew sizes to use with keys and shafts of various sizes. The table is titled, "Set Screws for Use Over Keys" (Ref: ANSI B17.1-1967, R1973). By implication, this would mean that the setscrews should be installed directly over the key, presumable to help keep the key from slipping. Any other use of the setscrew (i.e. on a machined flat) for anti-rotation would be redundant in this application.

If the purpose of the setscrew were to prevent axial movement, this would be a different case, however, drilling and pinning might be a better solution. If that is not practical (hardened shaft, etc.) then grinding a flat, groove, or notch on the shaft would be required. In this case, I don't think the setscrew radial location would be very important, as long as it did not interfere with the function of the key and keyseat or any other function of the assembly (e.g. inaccessible for removal, etc.)

I agree w/ Ried & Garthh. It's a bad idea to ever gaul up your driveshaft. Prevent that by all means. I would prefer a split hub that would allow itself to be 'clamped' to the shaft. The keyway would be located 180 deg. from the split. Be wary of the hub wall thickness. Use the set screw to further secure the key. Make sure 'lock-tight' is used on the set screw or make the screw long enough to use a nut to wedge it tight for vibration resiistance. Reference 'Machinery's Handbook'. If you don't have one, get one or buy one. It's like a math book. It has standard's and machinery fits that were developed before we were born, but is as applicable today as it was then.

I agree with carmieSD7 about split hub selection instead of set screw locking. Set screw locking is for "light" applications. If you are going to use split hub do not place keyway 180 deg from the split if you make the key - keyway with a clearance. Instead of 180 deg prefer 90 deg and ensure that the keyway is at the opposite side from where the threads of the split hub are. When we made such a connection for a roller chain application we discover a small "jump" of chain each time we tighten the split hub. We make a new chain sprocket with 90 deg the keyway with the split and chain work well