Electrode and electrode holder with threaded connection

Abstract

A threaded connection for an electrode holder and an electrode in a plasma arc torch is provided. The threaded connection has relatively low height, and the engaged portion of a male threaded portion of the electrode and a female threaded portion of the electrode holder are positioned at least partially within a nozzle chamber. In one inventive aspect, the nominal pitch diameter of the electrode is less than the minor diameter of the electrode. In another, the width of the root area of the electrode thread is wider than the width of the root area of the electrode holder thread by at least about 35%. The width of the root area of the electrode is at least about 15% wider than the width of the crest portion of the electrode. As such, the less consumable of the two parts, the electrode holder, is provided with a thread that is less likely to be worn and damaged. In one particular embodiment, the crest profile of the electrode is that of a Stub Acme thread separated by a larger root profile.

1 . A method of manufacturing the body of an electrode for a plasma arc torch, the method comprising the steps of:
 forming an electrode blank from a base material and defining at least one external cylindrical surface;   removing material from the cylindrical surface so as to define at least one helical thread form in the electrode blank, the removing step comprising the steps of;
 removing material so as to form flanks defining the thread form, the flanks defining at least one line when viewed in cross section that intersects at a crest apex with a line defined by another of the flanks and also intersects at a root apex with a line defined by yet another of the flanks, and 
 discontinuing the removal of material at a depth from the cylindrical surface that is above a depth halfway between the root apex and the crest apex. 
   
   
   
       2 . A method of manufacturing as defined in  claim 1  wherein the material removing steps define a crest profile for the thread form that is consistent with the crest profile of a Stub Acme thread. 
   
   
       3 . A method of manufacturing as defined in  claim 1  wherein the material removing steps define a root profile for the thread form that is not consistent with a root profile of a Stub Acme thread.