The Mitutoyo 505-721 dial caliper uses a dial to perform precise measurements to within 0.002", necessary for applications requiring the highest accuracy, such as in scientific research and in industries where parts must fit exactly. The Dial caliper is a refinement of the vernier caliper. Like the vernier scale, the dial’s measurement gives the final fraction of the total measurement to obtain a result with the highest accuracy. Instead of using a vernier scale, this caliper uses a dial mechanism to read this final fraction. This dial caliper takes inside, outside, depth, and centering readings.

The dial caliper has a fixed (main) scale and a movable dial, unlike the vernier caliper which has a second, movable vernier scale. The dial is circular and has a pointer; it is mounted on a toothed gear track which drives the pointer. As the dial moves over the main scale rule, the pointer typically rotates once every inch or tenth of an inch (the least count division) to give the additional fractional reading. The second measurement is added to the main scale reading to obtain an accurate result. The minimum measurement (least count division) of the dial creates the accuracy of that result. The main scale may be marked in inches, millimeters, or both. The dial is marked in inches or millimeters. The dial can be rotated beneath the pointer to measure size differential between two objects. A thumbwheel permits fast measuring and a rotating screw controls the caliper’s movement. The dial caliper is easier to read than the vernier caliper, thus safeguarding against user reading errors. Its standard of precise measurement complements the use of the vernier caliper; the dial provides an ease in reading and interpolating measurements which most vernier calipers, due to their need for direct observation of both scales, may not provide.

The 505-721 has a dial with a white face; the dial measures in inches. Its most precise measurement possible, or Least Count, is 0.002”. One revolution of the dial indicator needle equals 0.200" on the main scale. The dial uses a rack-and-pinion mechanism and is mounted on a gear track where each tooth equals one quarter of the dial resolution, and four teeth equal 0.200”. The smooth-moving dial is graduated in 0.001” and has gear train shock protection. A thumbwheel permits fast and easy measuring. A clamping screw controls scale movement and a dial calibration lock holds the sliding jaw’s position. The caliper is made of hardened stainless steel construction with a titanium nitride (TiN) coating on the beam wear surface to help extend caliper life. 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. Model 505-721 has carbide-tipped jaws for OD measurements. It has a Main Slide Length of 15.9", a Dial Length of 2.7", a Dial Height of 1.7", an Upper Jaw Length of 2.52", a Lower Jaw Length of 2.52", a Jaw Thickness of 0.15", and a Depth Measuring Blade Length of 0.79". Jaws are lapped to increase accuracy. Range is 0 to 12", Range per Revolution is 0.20", Resolution (Length) is 0.001000", and Accuracy is rated at + or - 0.002", 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 505-721 is supplied with a fitted plastic storage case.