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hardness of weld?

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  • hardness of weld?

    Hey,
    A friend of mine called and asked which is the harder weld, mig or tig? I have no idea and told him so. He is trying to repair a high wheel bike and one of the spokes was screwed up and in trying to repair it he broke off a tap and now must recover. What is your valued opinion?? I am not a welder of any kind. Thanks in advance Fred

  • #2
    I will say it depends on the rod/wire you are using to weld with not whether it's tig or mig. Heat has some effect on the weld also. The controlability of the weld may be better with tig as I have found it hard to do delicate welding with mig.

    I don't think you want to be welding to try to remove the tap on an antique. Perhaps have the tap EDM'ed out.
    Last edited by Carld; 11-23-2007, 04:02 PM.
    It's only ink and paper

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    • #3
      A lot of it has to do with how you let it cool down, depending on the material of course, but wrapping it in some fiberglass mat or equvalent keeps the cool down time slow and the weld will usually be easier to machine. Carbon steel weld build up can become hard and dificult to machine if your not careful.
      The shortest distance between two points is a circle of infinite diameter.

      Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

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      • #4
        Generally speaking tig welds end up being harder than mig but there are many exceptions.


        The issue here is removing a tap, though - not the weld. A harder weld is going to bust off everytime you try to turn it a mig weld is too messy to use for this kind of thing usually. Either way, welding to a HSS tap is going to be hard.

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        • #5
          If the tap is broken off flush or slightly above carefully tig a small piece of scrap to it for a handle using a stainless filler rod, it may take more than one attempt.

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          • #6
            a welding rod with a 70 in the front of the designation means the rod has 70k lbs tensil strength. mig and tig generally use the same tensil strength wire actually its the same wire.
            "the ocean is the ultimate solution"

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            • #7
              In my experience a mig weld is almost always harder to machine than a tig weld. With mig the deposit is laid in very quickly and the HAZ is small. Therefore the base metal will suck the heat out of the weld far faster than with tig. Tig being a slower process, the HAZ is wider and the weld cools slower.
              My favourite weld to machine is 7018. Seems to be the combination of the right heat input, a larger bead and a wide HAZ that allows the actual weld to cool slower.
              Russ
              I have tools I don't even know I own...

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              • #8
                Originally posted by J.Ramsey
                If the tap is broken off flush or slightly above carefully tig a small piece of scrap to it for a handle using a stainless filler rod, it may take more than one attempt.
                That is almost what I was going to say.

                Tell your friend to place a Hex Nut over the tap and weld the tap to it. then he can simply turn the tap out like a bolt

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                • #9
                  2nd or 3rd vote for welding a nut to it.One tip though is I would use tig with a stainless filler.Stainless sticks to and holds better on HSS.
                  I just need one more tool,just one!

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                  • #10
                    Originally posted by JoeFin
                    That is almost what I was going to say.

                    Tell your friend to place a Hex Nut over the tap and weld the tap to it. then he can simply turn the tap out like a bolt
                    Good idea but here's a twist. Tell your friend to tig a small washer to the tap...then tig the nut to the washer...it's easier to tig the thin washer than the deeper hole of the nut.
                    Actually, I'd heat up a 2"X2" cube of steel really hot with the torch. Then I'd heat that weld up cherry red with the tig torch. Plunk the hot cube on the weld and quickly wrap it with pink insulation (A new trick I've been using to weld hi-alloy axles on ATV's) and hold it in place with a bungy cord.
                    Let the weld cool for about an hour.
                    Then I'd weld the washer/nut and crank the kittle sukker out.
                    Russ
                    I have tools I don't even know I own...

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                    • #11
                      that will work, IF the tap also isn't broke length ways. it will just jam tighter if it is. what size tap? if it is splintered edm or just take a small punch and finish breaking the tap apart and dig out the pieces with a pick.

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