Ahhh - I haven't been clear in describing my options 
Option 2 is another way of achieving option 1, which is to change the 1/2" threads to M12 (option one through welding. Option two through the use of a slug). i.e. both fill the existing internal thread so a new one can be tapped.
Option 3 would provide a M12 thread by using an adaptor (the drwback of which is that the tool hight is increased).
All the options I listed are means to use only one drawbar.
Option 2 is another way of achieving option 1, which is to change the 1/2" threads to M12 (option one through welding. Option two through the use of a slug). i.e. both fill the existing internal thread so a new one can be tapped.
Option 3 would provide a M12 thread by using an adaptor (the drwback of which is that the tool hight is increased).
All the options I listed are means to use only one drawbar.
Hunting American dentists since 2015.