My "coupler" broke apart this morning. I was able to remove it by grinding down the 9/32" open end side on my craftsman combination ignition wrenches to just slightly thinner than the handle. The wrench now fits the shaft under the coupler. I made sure it was completely seated on the shaft by tapping it in. The coupler is left hand threaded so it comes off by turning it backwards. I had to use a slip jaw "water pump" pliers to turn it. It came right off. The good news is I didn't have to disassemble the blender at all. Keep the wrench handy to snug the new one on but do not use the pliers on the new coupler. Judging from the way my coupler came apart, they are easily damaged. It is just a plastic piece molded over a metal hub and it turns at high rpm so use caution tightening it securely without marring it or damaging it. I hope that helps.
Dale, January 2007