Re: Carbide Inserts for Rotary Electrodes

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Jon Danniken" <danniken@xxxxxxxxxxx>

Scott, thanks a ton for that information; it is greatly appreciated.  Please
do let me know if you are able to come across the part number for the gap
electrodes used in the Lincoln Electric TIG welders; that sounds like a
great ready made solution to try.

Thanks again,

Jon

> Original poster: "Scott Hanson" <huil888@xxxxxxxxxxxx>
>
> Jon -
>
> Most older commercial TIG welding systems utilized a simple spark-gap RF
> generator for starting the arc. These RF generators utilized replaceable
> screw-in tungsten electrodes. These electrodes consist of small tungsten
> disks 3/8" or 1/2" in diameter brazed to a short section of brass rod with
a
> threaded stud opposite the tungsten disk. These electrodes screw into
heavy
> brass blocks that serve as heat sinks and connection points. Somewhere I
> have the part number for the inserts used by Lincoln Electric for their
> older systems; I'll try to locate the data. Last time I checked,  these
> replaceable tungsten electrodes were about $12 each.
>
> Some of the "commercially" made rotary spark gaps use these screw-in
> elements as replaceable inserts for both the flying and stationary
> electrodes.
>
> Many manufacturers of industrial tungsten carbide cutting tools offer
> carbide "inserts" in the form of flat disks, 1/4" to 1" in diameter, with
> thickness from .1" to about .25". These are very easy to silver-braze to
> sections of brass rod to make carbide-faced spark-gap electrodes. An
> oxy-acetylene torch is required to get everything hot enough, especially
if
> 1/2" diameter or larger brass rod is used. I've used both paste brazing
> alloy (mixture of flux and powdered brazing alloy) and thin foil; SilFos
is
> one of the alloys commonly used for brazing tungsten carbide cutting
inserts
> onto the tool shank.
>
> In a spark-gap application,  tungsten carbide is not as erosion resistant
as
> pure tungsten is, but if you can get slightly used insert disks for a few
> dollars a pound they may be more cost-effective than paying $$$ for the
pure
> tungsten electrodes.
>
> Remember that for flying electrodes used in RSG applications you must keep
> the flying electrodes well below red heat to prevent melting of the
brazing
> alloy securing the carbide disk, which typically has a melting point of
> 1200 - 1400 degrees F. In any case, a scatter shield should always be used
> around the rotating parts or any RSG.
>
> Scott Hanson