Plasma electrode question

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When my electrodes from my plasma cutter get pitted, can I face them off in the metal lathe to resurface them off? I was thinking that I could get a little more use out of them before throwing them in the trash. I noticed that there is a spring behind the electrode that pushes it against the nozzle anyways so the amount of stock I take off would be taken up by the spring. Any thoughts?
Reply:When an air plasma electrode gets about 1/16" of a pit on the hafnium insert...the cut quality starts to get more angularity and dross....and in most cases the torch will occasionally misfire. Chucking the electrode in a lathe and facing off the pit will likely get a few more starts...however now the critical electrode face to nozzle inside bore dimension has been changed....so don't expect the same cut quality as you would with a new electrode.If you do the math (this is in regards to a Hypertherm Powermax65, 85 or 105 system)...the cost of the electrode and nozzle (this figures purchasing them at list prices) when cutting 1/2" steel at 65 amps works out to about 1/2 cent per foot. It is less expensive on thinner materials. By facing off the electrode you are adding shop time to this equation....and getting poorer cut quality....so my guess is that it will end up increasing your cost per foot of cut...instead of saving money!The purchase price of genuine factory plasma cutting consumables seems high....but when you break it down to cost per cut or cost per foot...there is no other process that comes close to the low cutting cost of plasma. I am talking about Hypertherm systems....which have the best consumable life...so if you are using a low cost import or an older technology plasma...the math may be a bit different.Jim Colt  Originally Posted by BrianstickWhen my electrodes from my plasma cutter get pitted, can I face them off in the metal lathe to resurface them off? I was thinking that I could get a little more use out of them before throwing them in the trash. I noticed that there is a spring behind the electrode that pushes it against the nozzle anyways so the amount of stock I take off would be taken up by the spring. Any thoughts?
Reply:The electrode has a tungsten in the center it is about 1/8" or so long. This is what wears, you must have it to withstand the heat of the arc, just like the tungsten in tig welding. Once this gets about half warn out it is time to change the electrode for more then one reason. The tungsten is past it optimum life, it may become lose and come out of the electrode.Here are a few pictures to show you what happens from new to blow out.The first electrode on the left is new, you can see the tungsten in the center. #5 electrode is done, used up. The last electrode is what happens when the tungsten burns or blows out. Attached Imageswww.georgesplasmacuttershop.comPlasma Cutter and Welder Sales and Repairs--Ebay storeTec.Mo. Dealer Consumables for the PT and IPT torch's
Reply:The center insert (emitter) of an air plasma electrode is actually hafnium (an earth element). There are tungsten electrodes for plasma cutting....but these are only used with non oxidizing plasma processes.....such as using nitrogen or argon/hydrogen as the plasma forming gas. If a tungsten electrode is used with either air or oxygen as the plasma gas it would only last for a few inches of cut, as tungsten does not live well in a high temperature oxygen rich environment.Mechanic makes an excellent point about the heat buildup in an electrode. The copper electrode body is essentially a heatsink that pulls heat out of the hafnium....ones the hafnium is partially consumed it does not transfer the heat efficiently....and when an electrode fails (as in the pictures) it can damage the nozzle and the shield in a plasma torch....ending up costing more than just replacing the electrode.Hypertherm has a new technology electrode in use for its Powermax65, 85 and 105 systems called copper plus....it actually has a self feeding hafnium element (the hafnium is longer, and auto feeds as it is being consumed) that maintains the correct internal dimensions while compensating for wear. These electrodes can last 2-3 times longer than the standard electrodes.Jim Colt  Hypertherm
Reply:Jim, Your right but everyone don't know what hafnium is and they can relate to the word tungsten. Its something I can show them and they can understand. Besides I don't have a stick of hafnium laying around the shop for show and tell.Now if you want to send me a 6" piece, my address is on my web site.www.georgesplasmacuttershop.comPlasma Cutter and Welder Sales and Repairs--Ebay storeTec.Mo. Dealer Consumables for the PT and IPT torch's
Reply:I know you know the difference....and almost everyone calls them tungsten....so I guess it doesn't really matter! The hafnium is pretty well controlled in our plant!That is a great picture to tell how to gauge electrode usage. It actually saves money to change them before they fail....in terms of bettrcut quality (less grinding) and on some torches the shield and nozzles will last longer.Jim Originally Posted by mechanic416Jim, Your right but everyone don't know what hafnium is and they can relate to the word tungsten. Its something I can show them and they can understand. Besides I don't have a stick of hafnium laying around the shop for show and tell.Now if you want to send me a 6" piece, my address is on my web site.