aluminum tube bending minimum radius chart

The k-factor has more than one definition, as we’ll discuss in future columns in this series. This 10- to 15-percent thinning during the bend forces the neutral axis to move inward, toward the inside surface of the material. Notice how the sheet has thinned at the bend. The neutral axis’s behavior is the main reason the flat part needs to be smaller than the total of the formed piece’s outside dimensions. The neutral axis position depends on the bend angle, inside bend radius, and method of forming. The neutral axis is the zone or plane that separates the tension from the compression.

The theoretical line of the neutral axis will remain the same length both before and after the bend is complete.ĭuring bending, while the area between the neutral axis and the inside surface comes under compressive forces, the area between the neutral axis and the outside surface is stressed by tensile forces. The neutral axis is a shifty guy that is, it shifts toward the inside of the bend. The neutral axis is a theoretical area lying at 50 percent of the material thickness while unstressed and flat. To understand the k-factor, you need a firm grasp of a few basic terms, the first being the neutral axis. The k-factor allows you to calculate the bend allowance, the outside setback, the bend deduction, and the flat layout of the precision part you’re forming. Once developed, the value of the k-factor will enable you to predict the total amount of elongation that will occur within a given bend. It’s a mathematical multiplier that allows you to locate the repositioned neutral axis of the bend after forming. It’s the base value needed to calculate bend allowances and ultimately the bend deduction. Of all the mathematical constants used in precision sheet metal fabrication, the k-factor stands out as one of the most important. One thing led to another, and I eventually found that to give a complete answer, my journey would take me not only to k-factor calculations, but the y-factor, minimum radii, kinetic friction, and grain directions-all key ingredients that make the sweet, subtle, complicated gumbo that is the science of bending. Where do these k-factor values come from, and how do you calculate them without a chart? The reader thanked me for the response, but then said he wanted to know more. I explained how the k-factor was used and referred him back to the usual k-factor charts. A reader wrote me asking me about the k-factor and calculating bend allowances. This is the first part of a two-part series. Describing that shift is what the k-factor is all about. The thinning sheet forces the neutral axis to shift inward toward the inside bend radius.

Aluminum tube bending minimum radius chart