I’ve got a 300w DC Spindle with basic speed controller with potentiometer (the standard things you’d find on a 3040 frame) and I want to start tapping holes in milled plates as an operation. So. Are these spindles reversible? I’ve been told that it’s a basic dc motor so there shouldn’t be a problem just flipping the polarity of the 2 wires.
So, in that case I can make an H bridge between the output of the speed controller and the spindle using automotive relays to keep everything electrically isolated. The relays I have are rated for at least 30 amps and I’ll be running everything on 24v (have we been keeping count over how many times people have told me to switch to 24v?) so there should be plenty of room.
I also think it might be cool to get an actual drill chuck mounted as an ER11 presents the challenge of swapping out the collet every time I want to change to a different size tap, but that’s a problem for another day.
Thoughts?
The main issue I found on 300w spindles is you can literally stop it with your bare hands at medium speed, which is not good for tapping. You can find geared DC motors with decent torque to do the tapping.
That’s an interesting idea. I could attach a chuck to a DC motor right on my machine as a separate head. Ok new topic: multi toolhead cncs?
Why not 
Even if you had a more powerful spindle, you will not be able to rigid tap on a gantry router. Even on a Tormach, you can’t rigid tap because of the precision needed to coordinate the Z axis and spindle. However, there are tapping heads that compress to make it easier to coordinate. See John Saunders’s video on tapping to see it in action: https://www.youtube.com/watch?v=JOb2Sg_Sg2I