Selecting a Vernier Caliper on Amazon.com
A vernier caliper has a main scale on its beam and a vernier scale on its movable jaw for reading measurements of the inside and outside dimensions of an object and the depth of a hole. The scales may be graduated in inch or metric units, or in both inch and metric units. For most vernier calipers, the vernier scale provides precision measurements to thousandths of an inch or hundredths of a millimeter. Vernier calipers have internal and external jaws plus a depth rod for taking measurements. To improve accuracy when measuring wide holes, a depth measuring base (also called a depth measuring foot) can be attached to the beam. Most vernier calipers have a locking screw to hold the jaws in place to take differential measurements, and a fine adjustment screw for precise positioning of the jaws around the object being measured. They are commonly used in fields such as metalworking, mechanical engineering, machining, and carpentry.
What sets a vernier caliper apart from other types of slide caliper is its simplicity of design, though it does take some practice to master reading the vernier scale. Because it has no internal moving parts, a vernier caliper is durable, requires little maintenance, and is not prone to inaccuracy caused by shock or contaminants. Although it is sometimes called a digital vernier caliper, an electronic caliper has a digital readout instead of the fine vernier scale found on a vernier caliper.
Vernier calipers may be fabricated from steel, stainless steel, aluminum, or brass. Plastic vernier calipers are available as well, and are best suited for classroom demonstrations. The material of a vernier caliper should be selected based on the environment and frequency of use. Sometimes the inside and outside measuring faces of the jaws have hardened steel or carbide inserts to provide a long life. Carbide offers improved wear resistance. The most common measuring range for a vernier caliper is 0 to 6", though there are extended range models that measure up to 50". Vernier caliper manufacturers include Mitutoyo and Starrett.