Choosing metal tubing for your project is confusing. You might grab a tube that appears right only to find that the fittings don’t fit, buy the wrong type of metal, or it bend under load.
There’s a chart that explains the interaction between outside diameter, wall thickness, and weight per foot. These factor impact what the tube can do. You must understand how weight, strength, and purpose relates to each other.
How to Choose the Right Metal Tube
A lot of folks assume that tubing is nothing more than a hollow piece of metal. That’s not a bad beginning; however, there’s much more to it.
Wall thickness is the variable over which you have control. You can have a very thick walled tube that appears exactly like another tube with a very thin wall. Under load they will perform different. Many do so. Buy based off only the outside diameter. Their handrail shakes.
The chart provide outside diameters in relation to wall gauge and weight. A very fine instrument tube would be a quarter inch in OD with a 0.035-inch wall. It is lightweight and precise. A fence tube might be two inches with a 0.120-inch wall. As the weight per foot go up, you know it has greater structural capacity.
The materials also becomes a factor. There are several different options: stainless steel, copper, carbon steel, aluminum. Each have its own qualities.
Carbon steel is inexpensive and sturdy. It will stretch until reaching 50,000 psi before giving out. However, it corrodes in the rain.
Stainless steel costs more money. It can holds up against corrosion very well. And it reaches a yield of 75,000 psi. That’s worth it if you’re putting them in water.
Aluminum is light-weight. It is about one-third the density of steel. This make it ideal for use on towers. But you pay for that with reduced yield strength.
Copper is also used for refrigeration and plumbing. There are three types of copper, K, L & M. K is the heaviest gauge (thickest). It is used for underground plumbing. M is the lightest gauge (thinnest). It is good enough for household water pipe. If you put the incorrect type of copper in the wrong application, you’ll get leaks.
Tubing comes in round, square, and rectangular shapes. Round tubing are strong in every direction. That’s why it’s the default for things like hydraulic lines and roll cages. On the other hand, square and rectangular tubing provide flat surfaces for welding and mounting accessories. For applications such as trailer frames and workbenches, square tube is typically best.
Standard sizes for each of these shapes is listed in the chart. These dimensions typically conform to ASTM A500 specs which standardizes your parts across various suppliers. That means no custom math, which saves time when you’re working on the weekend.
Next you need to connect the tubes proper. If you can solder it don’t TIG weld it (copper). Don’t try to solder a joint in structural steel. The infographic discusses joining types. The joining type determine whether you can take components apart. Fittings that compress let you disconnect. High pressure systems uses flare. Knowing your fittings matters. Having great tubing but connecting incorrectly will ruin your build.
Compare strength, weight, and price. Know what tubing to choose. Pick the strongest tube that fits in your budget.
Don’t over-engineer a simple shelf with heavy-duty structural steel. Don’t over-engineer a simple shelf with heavy-duty structural steel, but don’t under-engineer a load-bearing frame with lightweight aluminum. You should of use lightweight aluminum when building a load-bearing frame? No. Don’t use too much metal where it doesn’t matter. Don’t skimp on metal where it does.
The chart give you baseline information to help you not guess. It helps you understand how the numbers stack up. Once you learn the specs you don’t have to guess any more.
You build confidently. You know exactly what you’re looking for when you walk into the store. You walk out with the correct piece of metal. No trial and error. Right fit.
