The Mitutoyo 531-101 vernier caliper performs precise measurements to within 0.05 mm, for applications where the highest accuracy is required, especially in scientific research and in industries where parts must fit exactly. This caliper takes inside, outside, depth, and centering readings.

The vernier caliper has a fixed (main) scale and a movable (vernier) scale. The vernier scale moves over the main scale rule to give a fractional measurement which is added to the measurement of the main scale to achieve a more accurate result. The main scale may be marked in inches, millimeters, or both. The vernier scale may be marked in inches or millimeters. The 531-101 measures in millimeters. Model 531-101 has a spring loaded thumb clamp to control the sliding movement of the vernier scale. To improve visibility and readability and avoid parallax errors, the caliper has a modest face angle on the vernier scale.

The 531-101 measures in metric units. The scales are raised to slide easily and protect the graduation markings. A spindle loaded thumb clamp on the vernier scale locks the sliding jaw’s position, allowing scale movement only when depressed. The caliper is made of hardened stainless steel construction with a satin chrome finish. With its fixed and movable jaws, it has four-way measurement capability: outer diameter (OD), inner diameter (ID), depth, and step, where the butt end of the fixed jaw measures one end of a work piece before its upper/lower or inner/outer "steps" are measured. It has a Main Slide length of 229.0 mm, a Vernier Scale Length of 54.10 mm, a combined scale width of 29.97 mm, an Upper Jaw Length of 21.0 mm, a Lower Jaw Length of 40.0 mm, an Upper Jaw Depth of 17.0 mm, and a Depth Measuring Blade Length of 16.0 mm. Range is 0 to 150 mm, Resolution is 0.05 mm, and Accuracy is rated at + or - 0.05 mm, which meets Federal Accuracy Specifications GGG-C-111B.

Calipers measure the distance between two opposing sides of an object. They make inside, outside, depth, or step measurements, according to their type. Calipers are commonly used in architecture, metalworking, mechanical engineering, machining, manufacturing, carpentry, and medicine. The simplest calipers have two legs to mark the two points and require a ruler to take the measurement. More complex calipers use two sets of jaws instead of legs and have up to two graduated scales. Vernier, dial, and digital calipers all give direct and accurate readings and are functionally identical, having a calibrated scale with a fixed jaw, and another jaw with a movable pointer that slides along the scale. The vernier caliper has a scale sliding parallel to the main scale for an additional, fractional reading to improve measurement precision. The dial caliper has a circular dial with a pointer on a toothed gear rack replacing the second vernier scale. As with the vernier, this second measurement is added to the reading from the main scale to obtain the result. The dial caliper is used for measuring size differential between two objects, as well. The digital caliper takes the same sort of differential measurements as the dial caliper by zeroing the display at any point along the slide, with an LCD (replacing the dial) that displays a single, easily read value in both English and metric units. Some digital calipers can hold data readings between measurements and send them to data collection devices.

Founded in Tokyo in 1934, Mitutoyo is a leader in the metrology field, producing high-quality measurement products, including mechanical, dimensional gauging products, focusing on micrometers, calipers, indicators, and other measurement tools, as well as output gauges, interfaces, data collectors, and analysis software. Mitutoyo formed Mitutoyo America Corporation in 1963, which is headquartered in Aurora, Illinois, with additional locations in the U.S. and Canada.

The Mitutoyo 531-101 is supplied with a vinyl holster in a fitted carton.