This is the first of 2 videos on my Sherline Mill CNC Conversion.  The video is 12 minutes long.  I hope those of you with more experience can educate me, so that I can make updates and corrections.

Check out the second video of the conversion here.

My new drill press was a big improvement over my old 8″ Delta.  It has many great features and didn’t cost too much.  But I soon noticed a problem.

I noticed something strange about the speed chart under the top belt cover.  It represented a 5 tier pulley setup, but the drill actually has a 4 tier pulley.  That made it impossible for me to determine the actual speed of the drill.  I could still judge the relative speed, but not the actual speed and this really bugged me.

I needed a method to measure the speed of my drill press.  I have an oscilloscope  and I realized with a little rigging… I could use it to measure the speed of my drill.

First I coiled some wire on a nail.

I stuck a strong small magnet on the chuck and clamped the coiled nail near the chuck, so that the magnet would spin past the coils of the nail.

Eureka!  Once I hooked up the coiled wire to the oscilloscope and turn on the drill press… The magnet induced a small current in the wire that appeared on my scope.

Now all I needed to do, was to employ my college degree (BSEE) and calculate the RPM of the drill.

I repeated the measurements for the entire range of the belts on the spindles.  Then I graphed the results.   It’s interesting to see how non-linear the graph is.  I stuck the new chart on my drill and now I have a very exact reference for my drill speeds.