Identifying workpiece materials: General Industry Coverage

Machinists and metalworkers need workpiece materials to make parts. There are literally hundreds of different materials that are considered common.

When considering all the different metalworking operations a workpiece material might be subjected to during production, the knowledge required to keep track of the different material characteristics is daunting. A single source doesn’t exist to learn all these characteristics; unfortunately, most are learned the hard way.

At one place I worked, I was subjected to six distinctly different materials during my first 2 days. Each material had a specific set of do’s and don’ts.

For the modern metalworker, a solid knowledge of materials and their characteristics goes with the trade. When given an unfamiliar material to work with, take a minute to look up or ask about its common characteristics and potential problems. Some materials are so sensitive to common shop chemicals and substances that they can be permanently damaged without intentionally doing anything.

The ability to quickly identify different materials by their look, feel and mechanical qualities takes time to develop, but the practice required to learn how is well worth the effort. Any given shop has a varied cross-section of different materials—at least several dozen—that a metalworker meets. How many times have you picked up a piece of unmarked material and wondered exactly what it was? The following are some quick methods that can be used to minimize doubt.

The human hand and eyes are extremely sensitive comparative instruments—if you learn to trust them. Properly trained, they can discern minute differences in color, thermal conductivity, magnetism, density and mechanical condition. These are not absolute measurement methods, of course, but they help narrow the field and tip the scales in your favor when examining and choosing different materials.

The more you know about the different materials you work with, the more you will be attuned to each of their special qualities. This intimate knowledge of materials is especially useful when building or designing parts with different functional requirements.

Always try to make your comparisons with a piece of known material in hand. If you think something is 7075 aluminum, have a piece of known 7075 with you while checking the unknown material. This improves the accuracy of your observations.

Courtesy of T. Lipton

The small magnet on a pocket screwdriver can tell you a lot about a metal based on its level of magnetic attraction.