Sheffield Precisionaire Gaging


The Sheffield Precisionaire® Column from Precision Gage & Tool is the industry’s most accurate, dependable, and widely accepted air gage instrument. While its truly modular design is adapted to the same proven principles used for air to electronic gages for many years, today’s models are improved and simplified for increased reliability and operator convenience.


Modular gage design means that complete instruments in any combination of columns and amplifications can be assembled in minutes. Amplification is entirely pneumatic and linear over the full scale. Amplifications from 62.5 to 1 up to 40,000 to 1 are available. The graduated scales enable maximum and minimum tolerance limits to be set to allow plenty of “come-up” and “go-beyond” for accurate, easy reading.


Dramatically lower costs

With dependable air gaging, scrap is reduced, no usable parts are rejected—and many out-oftolerance parts are salvageable. Because inspection time is shortened, overall production time is reduced and machining processes can be brought under control more quickly. In many cases, costly high-skill man hours can be better utilized, as air gaging requires a minimum of operator training and skill. Finally, air gage size-sensing elements outlast conventional limit-type gages many times, and, unlike many ordinary gaging methods, air gaging allows easy compensation for gage wear.

Less Time, Greater Accuracy

All gaging systems using Precisionaire Instruments can accurately inspect up to 40 or more part dimensions in the same time it takes to check one dimension with a conventional gage. Side-by-side columns form a “float graph” which can be viewed instantly. Conditions and relationships such as average diameter, camber, squareness and other measurements which are extremely difficult to check are readily measured by Precisionaire systems.

Principles of Operation

The Precisionaire Column Instrument is essentially an air flow indicator. Pressurized air suspends a float in a transparent tube; this float moves up and down in the tube according to the flow of air. From the top of the tube, the air flows through a hose and exhausts through the clearance between the gaging device and the workpiece. The rate of air flow is proportional to the clearance, which is indicated directly by the position of the float in the column. Precise amplification and linearity are permanently built-in; the only moving part is the float supported on a column of air. The easy-to-read scale shows size at a glance.


Appropriate setting masters are used to establish the upper and lower limits of float travel in the column. These represent minimum and maximum part tolerance limits. Proper float travel between these limits are regulated by the external float positioning and calibration adjustments.

Internal or External Measurement

A typical gaging spindle has a central air passage and diametrically opposed air jets. It gages the true diameter of a hole based on the amount of clearance between the spindle and part inside diameter (I.D.); any change in air flow is directly indicated as a dimension by the float’s position in the glass tube relative to the instrument’s scale.

In the case of internal diameters, master setting rings have internal diameters equivalent to the minimum and maximum part tolerance limits and are used for calibration. For external checking, Airsnaps or Air Rings, with opposed jets, gage the part to indicate dimensional size. Master setting discs with external diameters equivalent to minimum and maximum part tolerance limits are used for calibration.

Single or Multi-column Flexibility

Modular Precisionaire Instruments can be adapted as desired for single or multiple, internal and external dimensional measuring. This modular “building block” design enables small, as well as, large shops to meet on-the-job inspection requirements with flexibility, speed, and economy. The modular columns and base panels can be stocked in the tool crib, ready to assemble quickly for immediate use.

Precisionaire Column Instruments can be used with all existing or new standard and special tooling without alteration. Standard 9” models are available in amplifications of 1,000, 2,000, 5,000, 10,000, 20,000 and 40,000 to 1; standard 15” models are available only in amplifications of 5,000 and 10,000 to 1. Conversion kits can be supplied for quick change to any standard amplification.

Conversion Kit

Convert modular Precisionaire Column Instruments from one amplification to another in minutes. The Precisionaire Conversion Kit contains everything you need, including column seals, float bumper assemblies, float, glass tube and appropriate scales. Kits are available for the following amplifications: 1000 • 2000 • 5000 • 10,000 • 20,000 • 40,000.