Guess This Tool Revealed: Spring Tubing Benders

This week's obscure tool is one way to bend small diameter tubing

Guess What This Is: #9
Vin Marshall

When bending metal tubing, the ever-present issue is the inherent desire of that tubing to buckle and fold rather than stretch in just the right places and bend smoothly. There are a number of ways to overcome this when bending tubing, but this is one of the simplest and cheapest: bending springs. Read on to learn how and why they work.

Picture a piece of tubing being bent. As the tubing bends, the material on the outside of the curve needs to stretch and bend while that on the inside simply needs to bend—it is essentially being compressed. This typically doesn't turn out well, and the inside part of the tubing will instead just buckle and collapse.

This is where tubing benders come in. The common theme among all tubing benders is to maintain the round cross-section of the tubing as it's being bent. The springs pictured are one of the cheapest, simplest and easiest to understand. They are inserted into (and sometimes also around) the tubing and provide support that keeps the top and bottom of the bend from bowing out and the inside of the bend from collapsing. It is similar in concept to what's known as mandrel bending. These bending springs are, however, only suitable for relatively small diameter soft tubing.