A Record of important things…

Mill Power Feed

Power Feed.  After milling for a bit it is pretty evident that a power feed is definitely a time and wrist saver.  I had a cordless Harbor Freight Hammer Drill that I never liked all that much that served as a donor for the motor and gearbox.  I stripped it down discarded the electronics and lathed off the notched ring that gave it the hammer action.
I used it as an exercise in machining to build a frame to hold the gearbox and make an adapter plate to fit the mill.


For airplane parts it is common practice to drill parts in assembly.  In this case however, I made sketches and machined all the parts to spec, being careful on all the measurements.  Even though not necessary, I was able to hold tolerances to +/- 0.001” on all dimensions.  Not bad for a noob.  Everything fit together with very tight tolerance and no play anywhere.  Satisfying.


To link the drill shaft to the X-axis lead screw, I machined a coupler with a tongue that mates to a slot already present in the lead screw, and then drilled a hole through the coupler and drill shaft. 

The coupler is threaded for a couple of 4-40 allen screws.  When they are backed out the coupler spins freely on the drill shaft in case I want to machine without the power feed engaged.  A little cumbersome and it it becomes a pain I will fit a quick-release pin instead of the screws.

IMG_2153 IMG_2151 IMG_2171

Speed Control for Power Feed.  Being hooked up on the Arduino, I whipped up a little PWM program.  It reads the voltage on a linear pot and adjusts a PWM signal output width.  I just used a DPDT-Center Off switch to change direction and turn it off, so the Arduino’s job is simple. Just read a POT, adjust the PWM pulse width and drive a power FET (IRFZ44).  A little Radio Shack Project box with the aluminum cover replaced with a 0.125” plate machined to accept the switch, POT, doubles as the heat sink for the FET as well.  Works great.