Neon Is Blackening Around The Electrodes
It is often a misunderstanding that the diameter of an electrode that is used is because it is being welded to a like diameter tube. The most important consideration is the milliamp rating of the electrode. Many 12mm electrodes are rated for at the most 30 ma and some only for 20 ma. Using an electrode that is not rated for the higher milliamps will shorten the life of the electrode considerably. Most electrodes for 60ma are 15mm so you will have to weld a 15mm to 12mm glass or change the specs to use a larger diameter glass.
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