How to Cap Square Tubing

Introduction: How to Cap Square Tubing

About: I am a hard working individual. I am into electronics and mechanics mainly but can get into anything if it has to do with making our lives easier or more enjoyable.

This Instructable will be about how to cap square tubing. I call it capping. You could call it covering the ends. Some might call it sealing it off. Others may say terminating the ends. Whatever you call it, this is how I go about capping the ends. I thought anyone who is working with square tubing might appreciate this technique, as I really like the way it ends up looking.

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Step 1: Get Your Tubing Piece Cut to Desired Length

I often use square tubing to create small brackets because it is strong, looks really nice, and is...well...square. In most projects, large or small, when working with square tubing its almost inevitable to end up with an open end some where. This is undesirable because in the outside environment it can collect water and dirt and begin rusting fairly quickly. Its hard to paint the inside of such tubing. I don't know if you've ever tried it...

Plus leaving this open hole on and otherwise really clean project in my opinion just looks plain unattractive.

Step 2: Cut Your Cap

Cut the cap! In this case, I'm trying to cap 1" square tubing. This is where I may do things a little different than others. You could easily go and cut yourself a perfectly square 1" X 1" piece of fill metal but I don't like this because it requires a lot of clean-up grinding to pull it off and make it look nice. You would almost have to bevel around the edge of the tubing so that when you ground it level after welding, there would still be a sufficient amount of weld holding your cap on. Now, if you're out there reading this and thinking..."wow, bevel?? Just for a cap?? It is a cap! There's no need for that!" I'll just say this, there is plenty of times when I'm making brackets for things that I later decide to weld something else to that said cap. In that case, I go on about my business well assured it has sufficient weld to hold things together. So! Cut your cap to fill only the hole. In this example, it would be .75" by .75". Don't worry about making cuts perfect. Close is close enough. In this case I'm using a sliver of angle iron out of my scrap bin as the donor for the cap.

Step 3: Fit the Cap

Test fit. If it almost falls in, its just perfect. If it ends up falling in, you can do what I do and put a small tack weld in each corner to keep it from falling down into the tubing whilst you tack weld the top on.

Step 4: Tack

Tack weld at least two corners. In most cases you'll be doing this by yourself as I was and you probably need to work quickly, as the tack weld will inevitably draw the cap up in the air. If you don't get two corners tacked before it draws, just grab the nearest blunt object and tap it back into place.

Step 5: Weld It Up!

Weld the gap between the top of the tubing and the edge of top of the cap. It may take a few times to get the speed right. In most cases you'll want to weld a quicker bead as opposed to perfect burn in. I take a minute to breathe out before I take off as it helps me relax and focus on following the lines and making a good bead. What I aim for is something I don't have to grind at all.

Step 6: Clean It Up

A quick wire brush and inspect your job. Don't fret if it didn't turn out perfect. If you look closely, this one isn't perfect, but it's good enough for the application. That's why I love working with metal. You can always grind it out and start over. At least for practice sake. Too many times and you're going to put some serious heat on your work piece. Heat=Distortion. Or I guess you could always just grind it smooth and round it.

Step 7: Finish Your Project

At this point you can finish your project. In this example, I used this piece of tubing as a mount for a inline filter mount on a sprayer. I fitted an older exhaust clamp that I cleaned up and welded it to the tubing at the right level. Then I welded the piece to the existing sprayer frame, cleaned, and then painted.

Step 8: Here Is Another Example...

Same project. I had to mount the pump lower than the tank for it to work properly. Gravity is your friend when it comes to water flow. I fashioned a pump mount out of various scrap pieces and some 2" square tubing. Its overkill for the application but I had to assume that an operator may run into a situation where the bottom of the pump mount would get hit on the ground going at spraying speed. Like maybe the operator goes over a really steep hill...or bank... Anyway, if you're curious the bottom is part of an old truck frame, and the angle piece is part of an old tractor track frame protection plate. The angle was perfect. The bigger tubing accepts these type of caps a lot better. It may be the fact that I'm using .035 welding wire too. I'm sure if I was using .030 wire and adjusted the amps, I could get a cleaner job on smaller tubing.

Hope you enjoyed this instructable and found it to be useful in your next welding project.

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    2 Discussions


    5 years ago on Step 6

    This is great advise and I use masking tape to hold the cap in place as I tack it.