RE: False sense of security, thread locker

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Leigh Copp" <Leigh.Copp@xxxxxxxxxxx>

This would be the standard way of securing a pin in a hole, but it
really doesn't address the issue of the set screws loosening off with
vibration, thermal expansion and contraction, time, etc.

The previous posts regarding the elevated temperature performance of
anaerobic thread locking compounds are spot on; Loctite 260 - a standard
"permanent" thread locking product - is designed to be service removable
at elevated temperatures, and loses 50% of its room temperature strength
at 150 deg C.

Loctite 272 high temperature thread locking compound is rated at 70% of
its room temperature strength at 200 deg C by comparison.

Given the application, if one were truly concerned about safety and
reliability, I would recommend pinning the tungsten electrodes in place.
Granted, this is rather difficult, as one would need to drill and/or
ream holes in the tungsten electrodes. This is possible with EDM
(Electrical Discharge Machining) processing, or laser cutting, but not
particularly practical.

Just a suggestion: Offset the set screw by nearly 1/2 the tungsten
diameter so that as it engages the circumference of the tungsten (with
high temperature thread locker applied), it imparts a twisting moment,
which "cams" and self locks the assembly.

Next: Make the set screw holes deep enough, so that a second set screw
can be jammed onto the first.

Last: If you are really safety conscious, drill, and wire lock the set
screw.

One additional suggestion: grind a flat on the tungsten, some distance
from the embedded end, thus leaving a step on either side of the flat,
so that if the set screw did back off slightly the electrode will be
loose, but will not fly out.

Leigh

-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: April 10, 2006 11:28 PM
To: tesla@xxxxxxxxxx
Subject: Re: False sense of security, thread locker

Original poster: CanalRay@xxxxxxx

When you make your rotary gap wheel the methods for holding the
electrodes into the
wheel vary greatly but after 30 some odd years in the machine trade
and with a good number of rotary gaps under my belt the ONLY way I
would mount the electrodes is by using a set screw at 90 degrees to
the axis of the electrode. Having a close fit in the electrode's
mounting hole doesn't hurt either. More work but more security.

Sincerely,

Tom Vales