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Don’t fight the power—Extension cords in the shop

This might not be the most exciting post I’ve ever written, but it could save you big money and downtime whether you’re a tradesman or a weekend fabricator. Choosing the right extension cord for the tool you’re using is often downplayed, taken for granted, or just overlooked as inconsequential.

Every now and then you see the question asked, “Can’t I just get one long cord and use it for everything?” Let’s go through why that is a bad idea.

Say you’ve got a 4 ½-in. angle grinder plugged into that old 16-gauge, 100-ft. extension cord you normally use for Christmas lights. It’ll run the grinder, but chances are you’ll notice the body of the grinder getting warmer than usual. Then hot to the touch. And if you’re having an unlucky day, the thing might just die. For good. Electric motors have to work hard to pull power over long distances; even with a cord in perfect condition, that thin wire at that length will not carry the amperage needed to keep the grinder’s motor running properly.

Now imagine you need only 50 ft. and the other 50 is rolled up out of the way. Because half of the cord isn’t exposed to airflow and juice is still running through it, the heat built up from the wire’s electrical resistance further drops its carrying capacity. In extreme situations, the heat from coiled-up extension cords can even cause a fire.

So, in this situation, heat is generated by the resistance of the cord’s small gauge, the length of it, the half that’s rolled up and basically cooking itself, and the draw of the grinder’s motor. Any one of those things is bad, but combined, your equipment will go south in a hurry.

Before we even started with that hypothetical scene we should have inspected the cord. Kinked and/or partially cut portions of a cord are more than just cosmetic damages, they’re also impediments to the flow of electricity, adding resistance and heat and lowering how much power is carried over the full length. It should go without saying, but a cut that exposes wire is a shock waiting to happen. Either throw it out the broken cord and source a new one or cut out the bad spot and shorten the cord. Depending on how much wire there is, you could grab a new male and female connector and make two smaller extensions.

In an ideal world, you should have multiple extension cords in various lengths in gauges thick enough to power your tools safely and effectively. It’s incredible how often this piece of the puzzle is left on the floor. A couple of years ago, I kind of flipped out on a friend when I walked into his shop and saw him running his dual-voltage MIG welder off a 100-ft., 16-ga. extension. I wish I had a dollar for every time someone told me how “this dumb thing” (aka, whatever tool they were using) was a piece of garbage that always overheated and died an early death, and how many of them they’ve gone through. Nine times out of 10, if you peek in their shop it looks like the Flying Spaghetti Monster took up residence in their workspace. Orange, black, and yellow cords plugged into each other, draped over and through toolboxes and cabinets and tables, and held together with electrical tape, spanning more feet than I could be reasonably asked to calculate are everywhere. And, of course, there are the power strips and splitters, which further reduce the power you can expect from a cord.

I have a bunch of extension cords, and mostly I try for overkill. I use 14/3 and 10/3 cords (the 3 means it has a ground wire too) for my Metabos. The 14 gauge is super short and comes in handy at the bench when I just need a little extra to hit the wall socket. The 10/3 is around 25 ft.; it’s heavy duty enough that I can run pretty much any power tool I have with no worries.

I’ve never killed a grinder in my shop. The oldest one I have, a 6-in. Metabo from my first year as an apprentice, actually suffered a sharp piece of falling angle iron on its cord about a decade ago, slicing it open. An electrician friend cut the cord at the slice and rewired the plug, then made me a hefty extension to make up the difference in length (when I need it). I’ve been using it ever since.

I just received my newest extension cord from the local welding supply store. It’s a 50-ft.-long, 600-V 8/3 cord that I can run my Dynasty 280 from. I have a 25-ft., 6-ga. version I made myself, but in the new workspace I needed something longer. In my experience, the Miller inverter-based machines like my Multimatic 215, Dynasty 280, and the 200 I ran off a generator in Iraq, do an excellent job of sensing how much power is available and adjust for it. Even so, you just don’t want your power cord to be the bottleneck.

If you’re ever on the fence, buy thicker gauge. I understand that there are times when you’re literally carrying the cords up ladders or across spans where weight matters, and at those times you can do the math to see what you can get away with.

Investing in a handful of high-quality, thick-gauge cords in different lengths is money well spent. Protect your tools, protect your shop, protect yourself. Don’t fight the power.

All images courtesy of Josh Welton, Brown Dog Welding.