Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>We have had it crack on a long 10 inch x 1 inch acrylic rod we used on a makeshift x-ray xmfr bushing.
I anneal in the oven now and never have cracking problems. Don't anneal and cracks may (emphasis on may) form.
Dr. Resonance
Tesla list wrote:Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx> Tesla list wrote:Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>We have used both black delrin and black (smoked color) acrylic with no HV leakage or tracking. When you tap the acrylic for the fasteners be sure to use kerosine if in a lathe. Also gently (very gently) anneal the acyrlic after tapping in your oven to prevent the sharp tap edge points from expanding into cracks that will radiate to the edge of the acrylic and cause fastener failure.I have never seen this happen. Drilling and tapping acrylic really needs some lubricant, or the acrylic melts or cracks too easily. Annealing acrylic is a temerity, as it shrinks and deforms with heat. The heat developed by tapping (with lubrication) is probably enough. Antonio Carlos M. de QueirozI have some tapping and drilling lubricant I got over 60 years ago; it's lasted a long time. Just rubbing the drill or tap with it (just poke into it) is satisfactory. Looks and smells like thick colorless shoe polish and is poured into a small cardboard tube about 1" diameter by about 4 inches long. Works beautifully for tapping anything I've tried it on, with the exception of stainless steel. Makes nice clean threads in acrylic. I wouldn't be surprised if paraffin wax or even bar soap would do as well and the soap would be easy to clean with water. Haven't tried it though. As Antonio says, tapping "dry" tends to be a most disappointing experience.Ed