Holematic Bore Gage Improves
Accuracy on F-22 Fuselage

Lockheed-Martin Gets .00015" Accuracies For New F-22 Fighter Program Fort Worth, Texas,- Sometimes the inability to drill or ream a hole accurately can make or break the functioning of a high technology aircraft, according to a manufacturing engineering specialist with Lockheed-Martin Tactical Systems in Fort Worth.

Here, where the main fuselage section of the Air Force's new F-22 fighter is being assembled, accuracy is a critical factor because of the exotic metals and other materials used in the successor aircraft to the well known F-15 fighter. Fred V. Fowler Co. is supplying that needed accuracy! Materials being drilled at the plant for both the F-22 and the F-16 include titanium/composite stacks as well as aluminum. "This is tricky," says Todd Lazar, "because the tolerances involved in assembling the new aircraft are much tighter than on the F-16. It's also more difficult to drill through a stack of composite materials." He explained that the drill first bores through the composite and then into the tough titanium, which can easily cause an enlargement of the first hole. To be sure the bored hole is precise, accurate measurement is absolutely necessary. "Until recently," he adds, "we haven't been able to access the different drilling depth levels with any degree of ease or precision to make the measurement." Previously, several methods were used for inspection, including dial bore gages and plug gages, but the results were imprecise.

New Holmatic Bore Gage	After acquiring the Holematic Mark II Pistol Grip instrument from Fowler/Bowers, however, Lazar indicates that his group can readily inspect the different levels in the layered materials.
With the new Fowler instrument Lockheed-Martin is obtaining accuracies to 0.00015" on the F-22, which the Air Force plans as its major air-to-air weapon. The Fort Worth plant assembles sections of both the F-16 and the F-22, which are produced at three other facilities. "Using the new Pistol Grip, we make our measurements three times faster. We estimate that we can measure 18 holes per minute with desired repeatability. Formerly, we could only measure six holes each minute on the F-16. And the setup times for both methods are the same," Lazar says. Covering a standard range from .040-12" (1-300mm), the Holematic Mark II Pistol Grip bore gage has improved electronics which include direct RS232 output, two preset memories, preset recall, tolerancing functions, and .00005"/ .001mm resolution. It has tungsten carbide measuring anvils on all 3-point, quick self-centering heads.

	Simplified Training Lazar says that after the instruments are assembled in the gage kits as desired, with the proper presets in the gages memory, operator training is "exceedingly simple." It takes approximately 10 minutes of 'hands on' training to become proficient with the gages for Lockheed-Martin's application.
Training is thus "at least twice as fast" compared to more complex gages. "You push once to activate it, then insert the probe into the ring gage, push the same button a second time, which presets out the gage, and, after placing the probe in the hole, you are ready to measure." Lazar also reports Lockheed-Martin is working with Fowler and British Indicators to develop a gage for measuring panel-to-panel flushness of gaps, which is vital for successful operation of the aircraft under all conditions. "The seams between fuselage panels have to be perfect," he says. The special gage developed by the two companies has replaced feeler gages.

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