TIG welding thin to thick
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  1. #1
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    TIG welding thin to thick

    Hey guys

    Trying to do a better job of my TIG on joining 1/8" to 3/8" steel.
    Using around 130A. Sort of splitting the difference as dont really know any better
    Seems like the thicker steel absorbs the heat .... and the thinner just melts/blows through ........

    Any tips on TIG doing this ? Preheat ? Setttings ? More time on the thicker plate until puddle forms then move quick though the thinner metal ?

    thx

  2. #2
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    Re: TIG welding thin to thick

    You need more amps. Need to be able to get a puddle on the 3/8". The control the puddle to melt the 1/8.

  3. #3
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    Re: TIG welding thin to thick

    Quote Originally Posted by tapwelder View Post
    You need more amps. Need to be able to get a puddle on the 3/8". The control the puddle to melt the 1/8.
    Thanks - so kinda whip through the 1/8th faster once the puddle is formed and slower on the 3/8th ?

  4. #4
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    Re: TIG welding thin to thick

    Hard to know on the amps until I know the weld geometry. Can you show the setup and results so far?

  5. #5
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    Re: TIG welding thin to thick

    Quote Originally Posted by sand_man_red View Post
    Hard to know on the amps until I know the weld geometry. Can you show the setup and results so far?
    Good point.

    And if you have a mass of 3/8 exposed I would start a puddle and wash it to the 1/8 metal. And refine things from there.

  6. #6
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    Re: TIG welding thin to thick

    Quote Originally Posted by tapwelder View Post
    Good point.

    And if you have a mass of 3/8 exposed I would start a puddle and wash it to the 1/8 metal. And refine things from there.
    +1

    Always focus more heat on the thicker piece, then work the puddle over to melt the edge of the thinner piece.

    Also think about how many "escape" paths the heat has to wick away from the weld area. For example, on a lap joint, start the puddle on the lower piece since the heat has two paths away from the puddle, whereas on the top piece, you're heating an edge, so the heat has only one escape path. If you try to focus the heat evenly on the bottom piece (with two heat escape paths) and the top piece (with only one heat escape path), you'll blow away the edge of the top piece before you get fusion. The same goes for a T joint. (A lap joint is just a T joint with one of the pieces flopped over).

  7. #7
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    Re: TIG welding thin to thick

    Sorry for delay.
    Dont really have a great pic - its this part here that looks tack welded. Mostly as I could tell it wasnt welding good so stopped.



  8. #8
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    Re: TIG welding thin to thick

    Your arc length is too long. Sharpen your tungsten with a long pointed needle sharp end and get that point in the nook and go. 1/8" is too thick to have to worry about melting through. If the tight arc is creating a cold arc then up your amps. This utter BS about using a blunted point and longer arc creating more volts is FUBAR. You should be able to weld that without filler for a root pass without burning through.

    Reverse logic but an argon/helium mix can actually create a smaller faster weld. I use it when beneficial.
    Last edited by shovelon; 09-21-2019 at 01:16 AM.
    Weld like a "WELDOR", not a wel-"DERR"
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  9. #9
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    Re: TIG welding thin to thick

    For something like this I'd usually leave my dial set around 175 amps and just use the pedal to get what I need. Hard to know for sure but I agree it's likely your arc length is too long. Keep that tungsten tip not more 3/32 of an inch from the root of the weld.

    Looks like a tough place to get into as well. If it's not easy to remove stuff around the weld to improve your access and vision then I'd consider redesigning the bracket so the welds that hold it in place present easier welding access. I'd also finish up all the welds on the sub assembly so you don't have to weld them all when the piece is in place. You could bring the bracket assembly either flush with the frame member or even lap it down the face a bit. And maybe box the ends in a bit so you can get weld around at least 3 sides of the box. Or clock the swivel from 6 to 9 and use a piece of heavier flat stock lapped onto the frame member.

  10. #10
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    Re: TIG welding thin to thick

    Went outside and measures steel with caliper. Its actually 1/8th to 5/32..

    So Im guessing I should start at around 160A ..... on the thicker base ..... and once puddle starts move along and sort of whip in and out of the thinner material a little quicker.



    sandman - good tip - the location is actually tight as you mention. Not terrible for the tip ... but hard for the filler feed and I cant weld opposite hands
    I didnt bring it flush to frame - only as Im not sure what clearance I will have with the sheet metal assembly. I might have to go get that just to see.

    Appreciate it.

  11. #11
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    Re: TIG welding thin to thick

    Just keep the tungsten buried in the corner of the weld and move it closer to the side that's not melting. Have you ever tried 'lay wire' technique for adding filler? You literally don't feed the filler, you just lay it down at a low angle (as if you were feeding it) and let the torch melt it in as you move the torch along. This method can help where it's hard to feed filler normally and actually makes a pretty consistent bead. You do have to watch your torch angle and keep it closer to perpendicular or the filler pulls away because it melts too fast. Maybe practice on the bench a bit before you try it on real weld?

  12. #12
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    Re: TIG welding thin to thick

    Quote Originally Posted by fakky View Post
    Went outside and measures steel with caliper. Its actually 1/8th to 5/32..

    So Im guessing I should start at around 160A ..... on the thicker base ..... and once puddle starts move along and sort of whip in and out of the thinner material a little quicker.



    sandman - good tip - the location is actually tight as you mention. Not terrible for the tip ... but hard for the filler feed and I cant weld opposite hands
    I didnt bring it flush to frame - only as Im not sure what clearance I will have with the sheet metal assembly. I might have to go get that just to see.

    Appreciate it.
    So thicknesses are almost the same but still irrelevant really as the edge your welding down to continuous piece is still going to try melting way sooner. Both are so thick though that you should be able to just weld it up. Get a base puddle going and scoot over until you can include your new piece and go.

  13. #13
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    Re: TIG welding thin to thick

    One more thing that's not clear to me in the photo, get all the mill scale and rust off the weld area, a good 3/8 of an inch on either side of the weld. Mill scale and rust lead to welds that don't wet out well and can also cause undercut.

  14. #14
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    Re: TIG welding thin to thick

    Got there in the end.
    Ran out of gas half way through. Not structural - so should be good.



    thx all.

  15. #15
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    Re: TIG welding thin to thick

    Quote Originally Posted by fakky View Post
    Got there in the end.
    Ran out of gas half way through. Not structural - so should be good.
    thx all.
    So the vehicle won't fall apart it's just your steering. No worries. Lol.

  16. #16
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    Re: TIG welding thin to thick

    Quote Originally Posted by danielplace View Post
    So the vehicle won't fall apart it's just your steering. No worries. Lol.
    Its the support bearinng. Has no load - think of it more like a guide to keep things straight.

  17. #17
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    Re: TIG welding thin to thick

    Quote Originally Posted by fakky View Post
    Its the support bearinng. Has no load - think of it more like a guide to keep things straight.
    Yes I see what it is doing. Giving the shaft rigidity at the U joint it doesn't otherwise get from the column. If it broke free it likely wouldn't be a total steering loss.
    Is it just a L there or does it go down to the frame on the other side of heim joint also ? You have enough gas to finish the top weld too where it looked like it was just tacked together also ?

  18. #18
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    Re: TIG welding thin to thick

    A better clean-up would have helped things!

  19. #19
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    Re: TIG welding thin to thick

    Quote Originally Posted by danielplace View Post
    Yes I see what it is doing. Giving the shaft rigidity at the U joint it doesn't otherwise get from the column. If it broke free it likely wouldn't be a total steering loss.
    Is it just a L there or does it go down to the frame on the other side of heim joint also ? You have enough gas to finish the top weld too where it looked like it was just tacked together also ?
    Well --- when I say run out of gas I should say .... I stopped there when I ran out of room on feed ... went to grab lunmch and turned gas off. Then forgot to turn back on when I cam and finished the run.

    Its sort of a triangle box. But most of that bracket is the main support. The boxing out just provides a bit more rigidity and cosmetic value. Its tacked on backside ... but couldnt get torch in there.

  20. #20
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    Re: TIG welding thin to thick

    Quote Originally Posted by Munkul View Post
    A better clean-up would have helped things!
    Good point. I keep forgetting how clean TIG likes ....... been doing MIG mostly .... but bought a TIG recently and just trying to use it more. Complete novice in both tho.

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