Thursday, June 30, 2016

Today's Machining Lessons

It took many hours to excavate a slightly off-center .27" deep hole in steel.  Lessons learned:

1. Use the coarsest and most powerful tools available to get close, then use machine tools to get it where you want it.  In retrospect, the next time I will drill a centered pilot hole on the lathe, use the drill press to enlarge that hole with 1/4" and 1/2" drill bits, then use the mill to enlarge the hole to .611".

2. As annoying as using edge finders is, it really matters.  Eyeballing where x and y are 0 produces off-center results.

3. Always start with stock that is as close as you can find to your desired final product.  I started with 1" diameter cold rolled steel, but I could have been stupid and started with a 3" x 3" rectangle and cut it down to size and shape with the mill.

4. Think carefully about material choice.  In retrospect, aluminum would have been a better choice.  I don't want this so strong that users can break a tap by putting too much force on it.  I had planned to use aluminum arms for that reason.  The body can be aluminum for the same reason.


  1. "... a slightly off-center .27" deep hole..."

    What does this mean? That the hole is off the center of the workpiece? Does the workpiece have to be centered on the machine?

    Or is it that the hole is not circular?

    "I will drill a centered pilot hole on the lathe..."

    How does one drill with a lathe?

  2. Off-center to workpiece.

    Drill with a lathe: put a chuck in the tailstock, put drill in chuck and advance tailstock into the pilot hole, slowly!