When to replace torch parts?

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So as some of you know, I got my hands on a TIG machine at last, and have been enjoying the learning curve.I did get some spare #8 cups and gaskets with the machine, and I started wondering what criteria I should use to judge replacement time for the cup.Obviously, physical damage means immediately getting tossed, but what else can go wrong with the cup that warrants replacement?I am getting ready to order some replacement parts and kind of want to know how much spare inventory is necessary.Thanks in advance for your advise on this.Papa H.Lincoln Idealarc 250 (circa 1962)Lincoln Weldpak 155 w/Mig KitLincoln Squarewave TIG 175
Reply:I just took a look at my 1.6 mm gas lens, and the screen was pretty boogered up with globs of metal.  I just used a pair of dikes to snip off the blobs (along with much of the outermost screen layer), and went back to welding.  It's lasted me a while like this (and this size gets the most use for me), and if it gets like this again, then it'll be time to replace.As for the cup, it's just there to direct the gas towards the weld.  It doesn't touch anything.If it's not broken, it can get blobs of metal stuck to it, but you can just poke those off with a screwdriver and keep working.  The only thing I can think of that would give cause to replace a cup that's not broken, is if it get contaminated with something oily, which could smoke as it gets hot.
Reply:Check your collets. Over time they will shrink, or worse crush. You can ask for the "high performance" collets over the Chinese soft copper collets, and be set for quite a while.Check the O rings on your backcaps. Your LWS has or can get the orange high temp ones if yours are getting shredded.The teflon cup gaskets wear out pretty fast too. I have to replace mine every 6 months or so.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Thanks fellas, much appreciated. Having been an equipment tech for many years, I am always asking myself when and why parts should be replaced when the failure isn't obvious to the naked eye.Shovelon, you might also be able to find the red silicon o-rings at the local auto parts store as they have replaced the use of paper gaskets with those in some automotive applications.PapaLincoln Idealarc 250 (circa 1962)Lincoln Weldpak 155 w/Mig KitLincoln Squarewave TIG 175