The Flex-Hone from Brush Research Manufacturing is a ball-style tool characterized by a shaft with small, abrasive globules that are permanently mounted to flexible filaments.
The Flex-Hone from Brush Research Manufacturing is a ball-style tool characterized by a shaft with small, abrasive globules that are permanently mounted to flexible filaments.

Sometimes the most experienced technicians or skilled toolmakers need to look to specialists outside when it comes to solving critical service problems. Such was the case when a legendary helicopter company was confronted with a worldwide problem in cleaning scale from a small, outsourced part that was preventing it from proceeding with production of its helicopters all over the world.

The problem was a carburized bearing surface delivered by a supplier of Sikorsky Aircraft Corporation, designers and builders of the world's most advanced helicopters for commercial, industrial, and military use.

“We attempted to remove this scale with a carbide reamer and a diamond lap - to no avail,” recalled Tony Lawrence, tooling services manager for Sikorsky Product Center Core Services. The material in question, according to Lawrence,  was 9310 [alloy steel], and very hard, around 66RC (Rockwell C scale hardness). This required a tool of equal toughness to do the job properly. Lawrence noted that his group had used diamond Flex-Hones, available from Los Angeles-based Brush Research Manufacturing in a very limited set of applications previously, but certainly not for this high volume situation they now faced.

The Flex-Hone is a ball-style tool characterized by a shaft with small, abrasive globules that are permanently mounted to flexible filaments. The tool, which can be mounted in a hand drill motor or a machine tool chuck, is used for finishing or resurfacing of the hard metals, ceramics and other tough materials used in items such as ports, sleeves, and cylindrical bores. Quite often the flexible hone is used instead of cumbersome conventional equipment such as CNC-based hones and anvil tools.

The flexible hone is available in many sizes with a wide selection of grit material, allowing the tool to be matched with a variety of materials from very hard, heat treated alloys to softer, non-ferrous. Custom sizes and grits are also available directly from the manufacturer. In the case of Sikorsky, the flexible hone needed to be constructed with diamond crystal grit. Brush Research offers a diamond flex-hone in a variety of mesh sizes that can easily produce finishes on hard materials to a range of Ra of 0.1 to 0.15µm. Sikorsky also needed the diamond hones in a very small size and in large quantities. Furthermore, it needed the parts in a hurry.

“So now that we had the first success, we were going to need to produce thousands of these [flexible hones], since we were at a production stop,” Lawrence stated. “We contacted Brush Research and explained our dilemma. Two days later we had the first production run of brushes, and we were able to ship our product again to customers all over the world.”

Grant Fowlie, Brush Research customer service manager, noted that custom orders such as this one require close coordination with his team and the customer, as well as some highly specialized equipment.

“Quite often the customer has a pretty good idea of what he is looking for in a flexible hone,” Fowlie explained. “For example, they know the size and hardness of the material they are dealing with and may even the kind of honing grit required. In cases like those, we may simply send one or two standard hones so they can see how the tools work for their application.”

Fowlie adds that in other cases his team requests samples of the material to be honed and then performs tests on site to ensure that the company’s recommendations are well founded. For this, sophisticated surface analysis equipment is often used. According to Fowlie, this free service for customers means Brush Research can run tests using a variety of tools to show the customer exactly what they are dealing with.

As Fowlie explains: “Surface finish analysis will give you roughness [Ra] and a variety of other measurements as far as surface finishing analysis goes, including peak height, valley depth, bearing areas and other specifications that have their own importance in different applications."

For the Sikorsky project, production of the thousands of Flex-Hones put a slight strain on the BRM staff, but Fowlie explains that the company is oriented to quick turnaround. Because Brush Research’s facilities are consolidated in a single Los Angeles location, orders are coordinated with efficiency and are normally shipped within days and weeks.

“This product worked better than expectation and the folks at Brush Research Manufacturing were unbelievably responsive," Sikorsky's Lawrence stated. "It doesn’t get any better than that."

For more information, contact Brush Research Manufacturing, Brush Research Mfg. Co., Inc., 4642 Floral Drive, Los Angeles, CA 90022; Phone: (323) 261-2193; Fax: (323) 268-6587; email: or visit the website: