Upgrade? Chinese CNC Machine

[John S]

Replied in that forum but it is the wrong place, only the original poster can post there. Everyone one else doesn't get a post reply button.

Anyway to keep it all in one place here's my reply.

This coupling question often gets asked.

There is only one design of coupling that can handle misalignment in two axis and still work. That is an Oldham coupling.

http://www.mekanizmalar.com/oldham.html

If you were in the UK I'd say Farnell, CPC, RS or Arc

The 2, 3, 4, jaw Lovejoy type couplings whilst being cheap are not zero backlash or able to handle misalignment in both axis.
The type you have I hate with a vengeance and is about as much use as a stick of celery and two hose clips.

REPLACE ALL THE COUPLINGS.