transmission couplings

[catchinit]

Generally what material would a basic transmission coupling be made from? By basic i mean a male and female coupling bolted together by say 8 hex bolts and has a keyway down the bore. Are they usually casted or are there other, better manufacturing techniques? Many thanks in advance for your time ;-)

[qapmoc]

Usually they are cast steel for ease of manufacturing but for a one off unit you could machine one out of solid steel billets. Some of the lower powered ones are also cast iron but this is very brittle and breaks easily.