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Re: Machining G10, machinist opinion



Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Jim,

My electrode holes were drilled 0.7" from the edge of the disc and does use set screws. The set screws are 1/4-20 threads at 1/2"L. Once they are seated against the electrode, the outer end of the set screw is inset about 1/8" below the disc edge. I've ran the disc up to 500 bps without any problems.

If your going to press fit the electrodes, there really is no reason to use set screws. Kevin did some analysis on the mechanical strength of using set screws or not. His conclusion was that the set screws could actually cause stress cracks. You might want to read through those posts if you haven't already.
The subject was called "FEA of new rotary spark gap".

Although I did use set screws (no stress cracks revealed), the disc was built long before this subject was every discussed.

Take care,
Bart



Tesla list wrote:

Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>

Hello All,

I have a 18"x 18" x 5/8" of G10 I took to my machinist who can make about anything. I could use some feed back on machining techniques to pass on. My first one was (12" x1/2") I made myself. Cutting this is the first. This one is much more massive and will have 1/2 " tungsten x 2.3 (12) pressed in. The feedback I got earlier was to make the holes .001 smaller and press the tapered tungsten in. How far from the edge would be wise? The set screw method directly into the G10 will hold them in place (I hope).

This will be on a variable asrg gap maybe up to 400 bps or > than or so.

Thanks,
Jim Mora