Welding Blow Through

Welding Blow Through


In an ideal world, this would never happen, but sometimes I find that I cannot cut away all damaged metal and must deal with blow through when welding patch pieces in. Do you have any tips/suggestions for minimizing blow through (other than cut more metal away)?


If you find yourself in a situation where you’re having trouble blowing through, you can clamp a 116” or thicker piece of copper behind the seam to be welded. The copper will keep from blowing through and will not be permanently welded to the weld itself. Sometimes the copper sticks a little, but a little tug or twist sets it free.

Copper Welding Helpers

There are also copper welding spoons available to hold, clamp or have an assistant hold on the backside.

There is also something similar available from Harbor Freight and others if you’re in a pinch. I’ve used plumbing connectors and copper pipe flattened out. Copper does dissipate heat quickly, so it’s helpful to know that copper will get hot. If you fab your own, use vice grips or something similar to hold it.

Wrench safe,

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5 Responses to “Welding Blow Through”

  1. Roger E Carlton

    Thanks for the welding tip. I have been experiencing the same thing while butt welding patch panels.

  2. Rich

    Magnets, use magnets to hold patch panels while you put in a couple tacks. So that your patch panel stays flush with the surface use something with a thin blade to pry the portion of the patch panel and hold it while tack welding other area of patch panel.

  3. Glenn

    Thanks good tip.

  4. william durdon jr.

    Please , on the GMAW safety welding ( very good by the way ) but more emphasis on welding galvanized and the problems associated with inhalation of fumes ( Zn fever ) should have mentioned respirator is a must with ventilation. Also with Chromium and other metals and salts. ( UV= down the road skin cancer sun blocker does not cut it William Durdon R.Ph. (also welder, a great challenging art)

  5. John Medina

    I hear there is a year of S-10 pickup that could be used as a chassis swap for the 3100 Chevrolet series pickup, could you tell me what it is please? Or any other comparable swap?