replacement part for acorn casement window operating handle

Hmm...It sounds like you're speaking about the worm gear of the operator has come out with the handle. Once that happens, the original part can not be repaired. You will need to replace the complete set. Take a look and consider our 39-141 crank operator. Compare the measurements in our part to see if they should match up with yours. This operator can be used with the 39-114L crank handle. Look over both parts and let us know if you think we found your match. 

Thanks for writing in! What I have used in this situation was to use the 33-205 Threaded insert nut. I would set it into the front recessed hole in the operator base and use a screw with a 10-24 thread. The screw would depend on the type and length you need for your particular window. You could also go to a local hardware store and purchase some "Acorn" nut or just a plain nut and screw to secure the operator.