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I broke a 3/8 extension bar while I was undoing a bolt. It broke into 2 pieces (2 blue lines) from the red line I drew in the following picture:

enter image description here

Is it possible to weld the 2 pieces together? Will it be strong enough for average use (below 50 nm torque)?

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  • If it really broke as you describe it likely was defective from the factory, and the reliability of welding it would be even more questionable than with two solid pieces.
    – Hot Licks
    Commented Oct 23, 2021 at 1:26
  • Interesting question .I usually brake the ratchet first .What is the torque rating of the 3/8 system?
    – Autistic
    Commented Oct 23, 2021 at 5:42
  • Maximum torque rating for a 3/8 drive is around 135 nm. I used it to break loose an overtightened crank pulley bolt which is why it broke. It was not defective from factory.
    – LFY MP7.3
    Commented Oct 23, 2021 at 15:12

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If you are a welder, yes. Chamfer both sides, and weld it. I'd say TiG weld it with 680 welding rod, tensile strength of 120,000 pounds per square inch. The welded area heat treats itself as its being welded. After grind off the excess weld and it'll be good as new. If you aren't a welder and would bring it to a welding shop, no. Cheaper and easier to buy a new one.

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Yes , no. To properly weld and heat-treat to original properties would cost possibly 100 X the cost of a new extension.

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    Keep it and use it as a drift - en.wikipedia.org/wiki/Drift_pin I was given a cheap one that clearly isn’t very hard. It is useful as a drift for punching stubborn large bolts out.
    – HandyHowie
    Commented Oct 21, 2021 at 14:46
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    If you broke it I would suspect it's low quality to begin with, trying to fix it is pointless.
    – GdD
    Commented Oct 21, 2021 at 14:51
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    Saw a high quality one loaded so much it had a 45 degree twist in it and when unloaded it was still straight. Can’t do that with cheap stuff…
    – Solar Mike
    Commented Oct 21, 2021 at 16:04
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    @NarimanAsgharian I'd put the dead one in the "stock" pile and in the future you might need a piece of steel for a bushing or similar. Having access to metal is convenient and saves buying some. On the downside, its probably mystery pot metal and not trustable for anything important.
    – Criggie
    Commented Oct 22, 2021 at 1:10
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    or (@Criggie) you might need a non-standard socket adaptor for something tricky. Either end could be useful then, welding a handle or something onto it, or grinding it to a custom shape. I've done similar on smaller scales (not even welded).
    – Chris H
    Commented Oct 22, 2021 at 8:20
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Getting a new, factory-made extension bar (or other common and mass-manufactured piece of metal) is both

  • cheaper, easier and faster (unless you happen to be pretty much away from some trading point)
  • gets you a better and more reliable product (subject to caveats as well).

No matter how good welder you are, you can at most restore the instrument to its original strength that was not enough to begin with (otherwise it won't break).

Depending on your working habits and abilities, you may use the pieces to create some non-standard tool, but if you are into this, you won't ask the question in the first place.

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  • It broke because I used it to undo an overtightened crank pulley bolt. 3/8 bars are not designed to withstand 200 - 250 nm of torque (maybe more). I used a 1/2 extension and didn't have any problems.
    – LFY MP7.3
    Commented Oct 22, 2021 at 16:45

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