Coaxiality of flexible couplings

It mainly depends on the diameter of the coupling! Our unit generally has no more than 10 lines on one side! Actually, flexible couplings are also very useful due to their high degree of coaxiality! Otherwise, the diaphragm keeps breaking!

Your question is too general; there are many types of flexible couplings. Among those I’ve come across are cross-slider couplings, universal couplings, and elastic kingpin couplings. The cross-slider coupling is used at the low-speed end of the reducer; high installation precision is not required. The coupling is also manufactured by us, so high precision standards are not necessary either. We have manufactured one universal coupling, which is used for connecting valve heads during valve grinding; the manufacturing precision of such couplings is not high. Universal couplings are also used for connecting equipment that requires dynamic balancing. The elastic kingpin coupling is used in the high-speed sections of motors, on the conveyor belts we manufacture; it is employed to connect the motor and the reducer. A higher level of installation precision is required, otherwise the kingpin may break, and of course the load applied cannot be too great.

The Couplings section of the Mechanical Design Handbook lists the allowable deflection angles for various types of couplings; you can take a look at it.

The scope of the question is too broad; I’m not sure how to answer it. What you mean is that the coupling itself is used to compensate for misalignment issues, so what is the acceptable level of coaxiality for the coupling itself? Generally, the coaxiality of elastic couplings should be within 0.1 mm, while that of diaphragm elastic couplings can reach 0.05 mm.