What tip profile?

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pointed ,pointed with a flat.For welding 4130 tubeing
Reply:are we talking tig/heliarc?IF it Catches...Let it Burn
Reply:Casarez,The purpose of putting a flat on the tungsten electrode is to help prevent "spitting" tungsten into the weld.  This is common for critical (aircraft) welds and automated welding.This is a good reference on tungsten electrode prep.http://www.diamondground.com/Guidebook0105.pdfAlso, a related thread from AWS forum.http://www.aws.org/cgi-bin/mwf/topic_show.pl?id=8185
Reply:casarez,I can tig weld myself.  However I think pulser is a much more qualified tig welder than myself.  I however would use the sharpended to a point for the chromemoly.  However, again I believe 4140, very close to 4130 is aircraft material and therefore perhaps Pulser is better qualified to give this explanation.IF it Catches...Let it Burn
Reply:Red,thanks for the compliment.  I don't know about being more qualified though.  I will say I am very interested in finding a logical reason for why we should weld one way or another.  Hopefully the logic comes in the form of some science or experimentation that someone can explain to me in lay-person language.
Reply:I would personally use a tip with a slight flat on the end.I think there are some compromises here either way, and much of it will be based on your own skill level, particularly in the start/stop area.  NHRA does not want you grinding on the finished weld, so if start/stops are difficult for you, the sharpened point may be a bit better.  Also, you won't be welding any grooves, so if you do have to do some light initial grinding at the start, it will basically be surface removal, no real digging.However, these are racecars, and the flattened tips will create a better penetrating, sound weld with smaller probability of fouling up the tungsten and introducing it to the weld pool.  However, it is a bit trickier to get started.Given the nature of the situation though, and considering the tubing you'll be working with, I'd use the flat tip with a bit bigger taper on it.