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Repair or replace?

Optical Depth Micrometers take the guesswork out of measuring scratches, pits and other surface marks.
Maintainers have the essential task of not just spotting damage, but also measuring it. These measurements are a major factor in determining whether a part can be safely repaired or will need replacing. This routine damage assessment process has a huge impact on resources and readiness. Preventing pointless repairs and unnecessary replacements ensures that maintenance dollars are spent where they are most needed. Spotting damage that is beyond repair during an initial inspection speeds up the procurement process and reduces ground time while waiting for new parts.

When a maintainer finds a scratch, they will typically refer to a specification or manual or consult engineering for the acceptable and repairable limits. Limits on surface damage are expressed in terms of depth, so it’s impossible to know the right course of action without knowing the depth of the damage.

Obsolete Methods

The “fingernail test” is outdated and inadequate, but unfortunately is still used as a way of evaluating damage. It’s not a valid technique that produces real measurements; as skilled as many inspectors are, none have calibrated fingernails. Ball scribes and pit gages have very poor repeatability on anything other than a smooth flat surface. Worse, the inspector has no way of knowing when geometry prevents the probe from contacting the bottom of the damage. This presents a very real risk of unsuitable and potentially unsafe parts remaining in service. Seeing the damage can expose potentially severe problems, like cracks in the substrate material, where NDT and further investigation may be necessary.

J Chadwick Co’s Solution

Optical Depth Micrometers (“Depth Mics”) are hand-held inspection microscopes that quickly and precisely measure depth, like optical height gages. The user simply focuses on the top surface next to the damaged area (Surface A) to establish a starting “zero” point and then focuses on the lowest point of the damage (Surface B).
Depth Mics can be used on most surfaces, including curves and corners, coated and chemically treated finishes, composites and transparencies. Measurement accuracy is +/- 0.001” with a magnification range of 40X–200X. They can measure depths of up to 0.250” with a maximum field of view of 0.180”. The newest 8600C “All-In-1 Kit” connects to a laptop or tablet and produces electronic inspection records with high-resolution images. It also has new accessories for inspecting complex surface geometries and internal diameters.
The commercial and military applications for this simple and practical tool are almost countless. Depth Mics are regularly used in commercial manufacturing environments to check dimensions for quality control purposes. The Air Force assigned the Depth Mic an NSN in 1996 as support equipment for the V-22 Osprey. Since then, it has been widely used across many platforms, including on the C-130 Hercules and F-16 Falcon and F-35 Joint Strike Fighter. In 2013, the Army added the Depth Mic as standard support equipment for most rotorcraft platforms, including the AH-64 Apache, H-60 Blackhawk and CH-47 Chinook.

More product information, videos, and case studies at www.jchadwickco.com. Call (626) 358-9955 or email sales@jchadwickco.com to discuss a specific application and arrange a free demonstration.

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