Wednesday, July 22, 2015

Embarrassing When You Forget A Skill

I was trying to square the end of a Delrin cylinder, and I can no longer do it!  I started the cylinder spinning, and then tried to run the cutting tool across the end.  At first, I blamed the tool not being shasrp enough, so I put in a new carbide-tipped tool.  Same problem: part way through the tip would grab the material and pull it out of the 3-jaw chuck.  Even using a dial micrometer to get the cylinder as close to square as I could did not help.  Is there something I have forgotten?


  1. Delrin is pretty slippery. Can you put a little texture on the surface the jaws are gripping?

  2. If you're using a right-hand tool, usually used for turning diameters, turn it about 45 deg CCW and cut the face from the inside. Otherwise use a left-hand tool to cut from the outside. Small bites.

  3. Delrin in a lathe is problematic. Can't recall the details, now. Maybe freeze it?

    Never did any personal lathe work on it. Little bit of milling, and don't remember anything of note. (Couple minor strokes, and other damage to memory.)

    Has to be supported when it extends much beyond the jaws, depending on the diameter. Too flexible. Very vague thought about it needing a different cutting technique/tool tip profile/depth/speed. That material is a major PITA to work.

    Keep most all solvents away from it, especially soaking. Chemical damage may not be obvious initially.
    Threads well. I seem to recall one part that was a female threaded block assembly that had a stepper motor for very precise adjustment. 80TPI, 3/8" to 1/2", maybe.