The QC type tool holders or Tormach style are set already for the length of your end mils. They will always be the same length when tightened into either a manual other type drawbar.
It makes no difference whether it is impact style or air actuator. I actually use a butterfly impact manually on mine with Tormach tooling. It's an R8 spindle.
Where this saves me time is even when I break an end mill, I can set another new one using my height guage and then continue milling from the last known good spot. No resetting of zero for the Z. Especially useful if doing work where the original surface is already milled away.
Power drawbars and quick change tool holders are two different things of course.
I only have a few of the endmill holders from Tormach, but they sure make life much easier.
I was working on an air cylinder drawbar, but it didn't work for my initial prototype. It wouldn't hold the QCTH tight enough when milling steel.
My newer design is with two of these cylinders. Should have p[lenty of oomph then.
