If you don't have machining facilities, file the end of the square shaft as round as you can get it and use a 'lovejoy coupling' (Google it). They can easily handle a fair amount of misalignment.
If you don't have machining facilities, file the end of the square shaft as round as you can get it and use a 'lovejoy coupling' (Google it). They can easily handle a fair amount of misalignment.