L.S. Starrett Co.
L.S. Starrett Co. Chordal Height Gage

Chordal Height Gage for Aerospace Components

July 14, 2022
A custom-designed and manufactured DO gage measures the opening heights of turbine vanes at specific locations to verify that an aircraft engine will receive the proper air flow.

THE L.S. STARRETT CO., a manufacturer of precision measuring tools and gages, metrology systems, and more, has introduced a custom designed and manufactured chordal height gage (a.k.a. DO gage) to be used for measuring the opening heights of turbine vanes at specific locations to verify that an aircraft engine will receive the proper air flow. The new chordal height gage is part of the Starrett line of special area-flow gages.

Even with the availability of hundreds of standard precision tools and gages, sometimes measuring challenges are best solved with a specially made gage, so the Starrett Special Gage Division designs and builds dimensional measuring instruments that provide guaranteed performance to meet customer specifications.

“Generally, to take turbine area flow measurements an operator must take the nozzle off the production line and bring it to an automated inspection machine, such as a coordinate measuring machine (CMM.) However, the special chordal height gage allows for rapid in-process verification of these parts, eliminating time lost on additional teardown and setup of machinery,” explained Starrett Special Gage Division engineer Kyle Webber.

The size of the chordal height gage is determined by the specific application  for which it will be used, and the new gage is no larger than a tissue box. Despite the small footprint the gage has three independent probes that are used to take measurements, including a free-floating central gage body that allows the middle probe to take accurate readings along the trailing edge, regardless of the variable contours that often are part of the nozzle design.

The gage is built in a “Lazy-L” shape to enable linear readings to be taken perpendicular to the trailing edge of the blades, giving a dimension for the smallest opening that air can flow through. These features help contribute to the accuracy and repeatability of the chordal height gage, which is within 0.0005 in., although the indicator readouts are generally set to a 0.001 in. resolution per customer requirements.

Learn more at www.starrett.com.

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