I purchased an old lathe with standard 20mm diameter headstock shaft with MT1 and 3/4" 16TPI end for attaching chuck. Unfortunately, the headstock shaft is bent and I replaced it with ER20 shaft (same 20mm diameter) that I already had but not able to use either MT1 chucks or regular "screw on" chucks.

Can anybody advise if there is a way to transition from ER20 taper and screw? Specifically:


  1. ER20 has male M25 x 1.5 thread and unable to find an adapter that would allow me to transition to male 3/4" 16TPI (for mounting chuck).
  2. Also, cannot find specs for the ER20 collet taper. Is there an insert for ER20 taper that would transition to MT1?
  3. If none of the two options work, is there a precision-made 3/4" 16TPI male thread that would have 1/2" 'tail' that I can insert into ER20? that way, I can hold the 'tail' in ER20 chuck and then use the protruding male 3/4" thread to mount the woodworking chucks? This third option would not give me MT1 but having a right male thread to mount chuck with jaws would be an acceptable compromise.



I know this is all complicated and my vocabulary probably is not very accurate to describe this but hopefully the question is clear. I tried to search for original replacement headstock shaft to no avail. Getting the headstock shaft replaced would be the best and easiest option but I gave up on finding it without paying several hundred dollars.

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