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How to Weld Large Gaps


Whether you’re working on small projects in your home welding workshop, or working on major repairs in the field, you’ll often encounter situations that require you to bridge large gaps with a weld. For example, you might need to repair a break between two sections of metal. If you don’t  have a suitable piece of scrap metal on hand to act as a patch, or perhaps it’s just not practical to use a patch, you have to fill the gap with a weld. In many cases, it’s easier to fill gaps with a weld, instead of trying to locate a decent piece of scrap metal from which you can fashion workable patch. The circumstances described above, along with a number of other possible situations makes developing your gap welding skills a worthwhile pursuit.

The following scenario illustrates an excellent example of a situation that requires large gap welding skills, in addition to demonstrating proper execution of this technique:

Let’s say you need to repair a break in a hand-railing (for this scenario, we’re going to assume you’re using a Mig welder), and you don’t have a suitable piece of scrap metal to patch the broken section. So what’s your best alternative? You guessed it: fill in the gap with a weld.

Here’s the concept at work:                                                                                                          

You fill a large gap with a weld by creating a series of bridges across the gap, with each successive bridge filling in the gap a little bit more.

Bridging the Gap

To begin, make the initial bridge with your Mig welder across the narrowest section of the gap, weaving back and forth with each pass, slowly moving the weld forward. The process begins at the narrowest part of the gap in order to build up more metal with each consecutive pass.

The overall weld must be created in series because the heat generated by the welding process will cause the metal to bubble, pop, and actually pull back against the weld, essentially eating away at the weld you’ve already created. The process is slow paced, as you should pause frequently, and allow the metal to cool after the completion of each bridge.

Going Deeper into the Gap

As you move forward into the larger portion of the gap, start forming your weld in a horseshoe pattern to build up more metal along the sidewalls, effectively closing the gap with each new pass of your “horseshoe” weld. The further you delve into the gap, the more breaks you need to take, because the sidewalls you’re building up consist more of filler weld than base metal, and the filler heats up more quickly than the base metal. Additionally, you should take longer breaks to allow adequate cooling time for both the base metal and the filler weld. As the heat builds, you may need to vary your technique, opting for something along the lines of making quick tack or spot welds on each side of your shrinking “horseshoe” shaped gap. Eventually, with some patience and perseverance, you’ll completely fill the gap, finishing off the weld.

Making the Weld Look Pretty

The end-product of the weld itself will not be very aesthetically pleasing. Gobs of filler weld does not look very appealing, and with an object like a handrail, you want a presentable appearance. Fortunately, with your convenient hand-held grinder, you can shape the weld and clean-up the metal nicely to create a smooth, seamless repair—casting the illusion that the handrail was always of one continuous piece of metal.


Dylan B.


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