This is the coupling from ASAP supplies , as mentioned it is milled and also has the extra crimping bolts over the cast from BuckAlgonquin. I would also venture to guess that the extra bolts are to compensate for the lack of a keyway.
I guess it is going to come down to being able to to get the keyway milled and associated cost, as apposed to going with one that is ready to go and cheaper, but not as good a product.
Another issue with the cast, what I have now, is the corrosion
which is basically why I want to change it out. Would the milled steel
coupling be any less corrosive?
that you have no key and experianced no issues, I see you also have the flex coupling installed.
As you are the only one so far that responded without a keyed coupling, I am still leary on just relying on the crimp bolts and set screw even if there are an extra set of them.