About Machinist Metalworking Calipers

Measurement is an important task when it comes to the machinist and metalworking. One of the tools that is most used for this task is calipers. Calipers come in many variations some of which transfer measurements and some which show the measurement directly. This article will describe all of the aspects of metalworking calipers.

History

The first known pair of calipers was found in a Grecian wreck near Italy, dating around the sixth century. Since, there are rare finds from both Greek and Roman sites. On the other side of the land mass, the Chinese utilized bronze calipers marked with the date of creation. The vernier caliper as it is now used was created in 1851 by American Joseph Brown. Since, the Brown and Sharpe Company has been the company for the manufacture of precision measurement devices.

Transfer Measurement

Calipers whose use involves the transfer of measurement are the cheapest and simplest to use. Measurements are made in an indirect manner by transferring a length to a ruler or micrometer. These come in four varieties--inside, outside, dividers and hermaphrodite. Inside calipers are designed to measure the inside of features, such as diameters and gaps. Outside calipers similarly measure the outside of features. Dividers are used for the even spacing of features and the transfer of identical lengths. Hermaphrodite calipers are used for measuring from an edge or corner.

Direct Measurement

Direct measurement calipers show the measurement without trying to transfer the measurement. These come in three varieties based upon how the measurement is read. The first kind is the vernier caliper. This kind of caliper features a graduated ruler, along with a vernier scale for reading fractions of an inch. The second kind is the dial caliper. These feature a small rack and gear that moves a dial pointer around a circular face for measuring the fractions of an inch. The last kind, and easiest to read, is the digital caliper. These feature an electric circuit that measures the motion of the caliper and provides a digital output of the measurement.

Features

All calipers feature a reading of at least one thousandth of an inch. Higher end models can measure down to ten thousands of an inch. The direct reading calipers also feature four ways to measure features, including inside and outside measurements, depth measurement and step measurement. Additional features include fine adjustment of the jaw width, friction control of the jaw opening, imperial and metric measurements and more.

Usage

To use calipers requires a fine touch. The jaws are opened or closed onto the feature to measure, making sure to stop the process right when the jaws first experience resistance, but not past. Once the jaws are at a fixed opening, transferring calipers are then measured against a ruler. Direct measuring calipers are read directly without removing them. What is most important is that a fine touch is used and that measurements are repeated to ensure accuracy.