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Full penetration weld question

Posted: Sat Jan 23, 2021 1:00 am
by lr172
Hobby welder, new to tig here and making my welding table.

I will be tig welding 2 - 1/8" 2 X 2 Tubes together and would like a full penetration weld for strenght. I will use a 1/16 or 3/32 rod to leave a gap. Do I need to bevel, or will I be ok with this small thickness. I have done a few practice butt welds with a gap and seemed to have a good amount of metal on the backside when done. Also, Can I do this in one pass or should I be doing a root pass and a cap of some sort. My practice runs seem to look pretty good with one pass.

Thanks

Re: Full penetration weld question

Posted: Sat Jan 23, 2021 1:04 am
by Oscar
On 1/8" thick material I can't see the need for a any bevel/root/cap pass unless your TIG is severely under-powered. I also can't see the need for any sized gap. How much amperage do you have on tap?

Re: Full penetration weld question

Posted: Sat Jan 23, 2021 1:50 am
by Spartan
I TIG and MIG 11ga 2x2 tube structures almost each week. I always cut a bevel to about 1/16" land. No gap. Single pass almost always, unless I need to get up over a corner roll on some joints.

The bevel is a good habit I think, but not completely necessary based on your application.

Putting in a root gap as you mentioned is advanced welding, and completely unnecessary for you to do when building a welding table....unless you want the practice of doing it.

Re: Full penetration weld question

Posted: Sat Jan 23, 2021 8:56 am
by cj737
Gap or not, you can get all the penetration you need with your TIG. What is more beneficial is to actually clean the inside of the tubing where you butt the weld. If you gap, and don't clean it, you're sucking all that mill scale, grime and crap into your puddle. Take a Dremel and clean back about an inch.

Gap it with 0.035 MIG wire (2 pieces, bent into Vs to spread the tubing). Tack it using 3/32 filler. Jerk the MIG wire out. Take your time and stuff the filler in as you go making sure to get the filler INTO the puddle, not ahead of the puddle. You will have a fully penetrated weld that you can blend down on the outside without losing strength.

Re: Full penetration weld question

Posted: Sat Jan 23, 2021 10:29 am
by lr172
Thanks for the guidance on this. I have a Primeweld 225, so plenty of amps. I have been using 120 for all of my practice and plan to use that for this also. I think I will experiment with both the 035 gap and the bevel with land on these. Figure it is more good practice. On some of my practice butt joints that were pushed against each other with no bevel, I was not seeing full penetration on the back side; Likely due to my inexperience. I was seeing some, just not the whole weld.