My NSK EMax is attached with the reducer, I was just wondering if it’s possible to still run the EMax over 4 rpm, to something like 20 rpm with the reducer still attached to the hand piece.
You need to supply a little more information. Is the speed reducer a model RG-01 ( 4:1 reduction) or a model RG-02 (15:1 reduction)? What model is the hand piece? ENK250T is rated 1000 to 25000 rpm and ENK410 is rated 1000 to 40000 rpm.
If you look at the reducer, it will have a maximum speed input rating etched on the barrel. Mine says 30,000 rpm. You should be good to run the motor at 20,000 rpm which will give yo a 5,000 rpm output speed. 7500 rpm out (30,000 rpm input) is the maximum through the RG-01.
If you need anything higher that 7500 rpm output, you can remove the reducer and go up to 40,000 rpm.
I have two of the pin spanners so I can hold the motor assembly in place and loosen the gear reducer. Big end on the motor assembly (on the plastic collar adjacent to the gear reducer) and the small end in the hole in the center of the gear reducer. No issue with removal just holding the motor assembly by hand for me. You do need the wrench on the gear reducer and probably the collet assembly.
My kit came with two of the pin spanners. If you only have one, a rubber kitchen glove or something like that to give a better grip on the assembly may help.