Quality Digest  |  12/02/2008

Borescopes Bring Positive Change

Gradient Lens Corp. Hawkeye Precision Borescopes

A Tell Tool technician using the Hawkeye borescope for part inspection

A mix of mission-critical components for high-stakes applications makes visual inspection a key part of the process for Westfield, Massachusetts, manufacturer Tell Tool Inc. The company manufacturers complex machined castings, forgings, and wrought material for aircraft and spacecraft, so quality control is important to Tell Tool, an ISO 9001- and AS9100-registered company.

For products such as electronic engine controls, hydromechanical fuel controls, auxiliary power units, pump housings, and jet fuel control housing, blueprint requirements are stringent. “If the part doesn’t meet blueprint tolerances, Tell Tool must reject it,” says Michael Ostrowski, head of Tell Tool’s purchasing team. “There’s no repair allowed; the customer will not receive the part. It’s that critical. If a burr were clogging a passageway when the engine is calling for fuel, you could have a catastrophic failure of the engine.”

In the past, Tell Tool met quality demands via manual, time-consuming methods such as making impressions or visual inspection with only the naked eye. The process involved highly skilled machine operators who physically looked inside components, or the quality lab made impressions of parts to identify defects. Both manual processes took a good deal of time and were prone to error, leading to waste that affected profits. Also, if a customer required 100 percent inspection, throughput and productivity went down.

Fine tuning the inspection process is vitalbecause, on average, each part the company makes consists of 5,500 features that require checking. “Some even have 10,000 features,” Ostrowski says. “Only a handful of other companies can manufacture the parts that we do.”

The introduction of Hawkeye precision borescopes, made by Gradient Lens Corp., located in Rochester, New York, allowed Tell Tool to visually inspect 98 percent of the interior cavities and cross holes for burrs and surface finishby magnifying the image of the surface detail from directly inside the component or part with exact precision. Borescopes are ideal for specialized applications such as inspection of castings, bent tubes, turbochargers, engine blocks, and turbine blades. They are a key component in Tell Tool’s visual inspection process because of complex geometries that are common in its products. At present, Ostrowski estimates the company utilizes nearly 50 Hawkeye borescopes.

Tell Tool employs certified machine operators who inspect pieces rolling right off the machines, as well as quality staff, some of whom are designated suppliers’ quality representatives. The inspection process incorporates software that tells the operators which characteristic to inspect. By the end of the process, all inspection results are accumulated in a database and documented.

A quality committee conducts monthly reviews for all quality assurance issues, identifying any deficiencies in Tell Tool’s manufacturing process, tracking defects through data it collects, and acting on that data. “We make everything adhere to the blueprint,” says Ostrowski, “and offer value in giving customers a part they can rely on.”

In some cases, customers set their own quality levels, specifying how many pieces Tell Tool must inspect per lot. A positive change resulting from borescope use is that when Tell Tool quotes on a job that requires borescopic inspection, it will take over the borescope inspection that the customer would usually do.

“Where the customer used to do the inspection in-house, we now do it,” says Ostrowski. This has helped reinforce customer relationships and add a new profit base to the company.

In addition to its general manufacturing area, Tell Tool uses borescopes in:

Deburring. This area is the heaviest user of borescopes because cross holes in parts often have burrs that have to be removed.

Electrical discharge machining. Operators in this area check inside cavities for burns.

Extrusion/honing. Here, a machine pumps abrasive putty through flow chambers to polish them, and operators check pieces after that process.


Gradient Lens Hawkeye precision borescopes allow Tell Tool to check for thousands of features without resorting to manual methods. The borescopes have improved accuracy, eliminated waste, increased profits, and broadened customer relationships.


Gradient Lens Corp. Hawkeye Precision Borescopes


  • Inspects interior cavities and cross holes for burrs and surface finish
  • Checks thousands of features
  • Improves accuracy, eliminates waste, and increases profits.




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