Rigid Type Couplings
The two most prevalent types of "Rigid" coupling (one that has little to no misalignment properties) are the "Flange" and "Sleeve" (or "Muff") types, as shown above. These are used by customers, and in applications, where it is imperative that the rotation of the driven load is critical.
A "Flange Coupling" is composed of two shaft hubs with proper bore, each hub having an integral flange, and high strength bolts for clamping the two hubs together. Torque is transmitted between the two coupling shaft hubs through the bolts and flanges. Manufacturers will differ in their explanation of the actual method of torque transmission, however. Some will say that the clamping action of the bolts through the flanges will cause very high friction of the mating flange surfaces and that friction is what transmits the torque. Others will tell you that the bolts are the actual torque carrying component. As for me... with zero design background in couplings... I really believe it will end up being a combination of the two.
The other type of rigid coupling, is the "Sleeve Coupling", sometimes referred to as a "Muff Coupling". This design of coupling is simple in it's construction. It is basically a "pipe", or steel rod, bored and keyed through it's length to the proper dimension, then split in half (lengthwise) and held together with cap screws. You can see it's basic design in the picture above.
This coupling has ZERO tolerance for misalignment and also has ZERO maintenance required during use. In the smaller sizes, i.e. fractional and micro horsepower sizes, the coupling may not be split lengthwise, nor will it be keyed. Instead, it will be held in position on the mating shafts with standard "Allen Screws" and they will be the object that transmits the torque between the driver and driven equipment.
So if you're in the market for a "Rigid Coupling", pick your style and give us a call. We'll do our best to answer any questions for you and assist you when necessary.