Quote Originally Posted by Snapper View Post
Every chinese spindle I have seen actually has a 4 pin plug on top so you can hook that up on the bottom to a bolt inside the spindle housing (under the cap) and then if you get a 4 core CY cable for your spindle you can run your earth with that, which is the best and tidiest way to do it imo. For a quick fix for now just take any bolt out of the frame (away from the cutting area and any moving parts) and get a piece of cable, crimp a ring terminal on the end of it and bolt it down to the frame, connect the other end to earth. That 'may' help your problems a bit short term, but shielding that spindle cable is going to be of more help. VFD emits a lot of EMI, and doesn't play nicely with USB or other low voltage electrics.

Your problem could also be mechanical, misalignment somewhere or something, or even a weak PSU that is struggling to drive 2 axes properly simultaneously. The power supplies they send out with these things really are a pile of crap (mine ended up setting on fire )
Also, where are you based? Someone from this forum might be able to pop in and take a quick look.