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Bridge Tool & Die: CNC Turns ‘Feel’ Into High-Precision Carbide Grinding

Jim Lorincz
By Jim Lorincz Contributing Editor, SME Media
At Bridge Tool & Die, CNC grinding technology from United Grinding turns the expert “feel” of manual grinding into “facts” that help optimize the grinding process. Photo courtesy Dwight Cendrowski

Glenn Bridgman describes the difference between his shop’s manual grinders and its newest state-of-the-art CNC ID/OD grinder, a Studer CT960 OD/ID from United Grinding (Miamisburg, OH), as “feel vs. facts.” Bridgman, president of Bridge Tool & Die (Buckley, MI), believes that manual grinding is a somewhat personal operation. The machinists are physically closer to the process and can hear and “feel” it, he said. On the other hand, he sees today’s advanced CNC grinding technology as a way to turn that expert feel into cold hard facts and numbers. Those facts ensure a much more repeatable process that significantly boosts the shop’s workpiece consistency, quality and precision, as well as its production output.

With his substantial background in grinding, Bridgman bought the company he had been working for and created what is now Bridge Tool & Die. And with the purchase of the shop came decades of grinding experience, particularly with grinding carbide, which remains the shop’s specialty.

Bridge Tool & Die grinds carbide and encases it in steel for tooling used in high-volume extruding and forming processes, producing tooling and other components for the mold and die, oil and gas, and automobile industries, among others.

“Carbide is an extremely hard material to grind,” explained Bridgman. “It requires diamond grinding wheels. But most importantly, the process involves finesse in terms of speeds, feeds and material removal rates. That is why we acquired the CNC technology. We not only needed predictability and consistency, but also an increase in our capacity.”

Bridge Tool & Die’s new Studer CT960 does both ID and OD grinding. Its indexable head houses three ID spindles and one OD spindle, plus a probe. The shop can run an operation, have the probe check the part and, if needed, tweak the program on the fly.

According to Bridgman, the Studer CT960 dramatically shortens setup times and eliminates the need to move parts between as many as five separate OD machines before completing the part in an ID machine. Instead of these five individual setups on five different machines for one component, the Studer CT960 completes the part in a single setup.

According to Greg Mort, the B-axis capability of the Studer CT960 has been a game changer when it comes to grinding radii, producing perfect radii while also eliminating much secondary benchwork. Photo courtesy Dwight Cendrowski

For its wheels, the shop uses a variety of diamond wheels, ranging from metal bond to dressable vitrified for finishing operations. The machine tracks the wheel size, limits and corrections in a tool library that makes part setups even faster. Wheels can be loaded, unloaded and reloaded again and be in the exact location every time.

Many parts require small ID ground holes, which is why, according to Bridgman, the shop gets the speed it desires from the Studer CT960. He explained that the smaller the hole and the smaller the grinding wheel used to create it, the higher the required spindle speeds. Higher speeds allow the small wheels to act harder and grind with fewer breakdowns, and for this, the machine delivers 42,000, 45,000 and 60,000 rpm spindle speeds. The shop also has the option to boost its top speed to as high as 120,000 rpm.

How the Studer CT960 turns feel into facts, according to Bridgman, is through its StuderSIM software. It shows a live simulation of the wheel position, spindle speeds, and feed rates while providing acoustic grinding feedback on the workpiece and dresser. Plus, it allows the shop to run offline simulations to avoid problems during actual part runs.

“We considered other grinder brands, but from a quality point of view, the Studer CT960 was far beyond the others, especially in terms of precision and software,” said Bridgman. “StuderSIM really sets the machine apart from the competition because it is software designed specifically for the grinding process. Others just try to adapt conventional milling or turning machine software to grinding operations.”

In addition to its software, Greg Mort, business manager at Bridge Tool & Die, finds that the Studer CT960’s B-axis has improved the shop’s ability to grind radii. It allows the workpiece to swivel as it’s being ground and thus produces perfect radii.

“Especially beneficial for part radii, the machine eliminates the need for secondary hand polishing to achieve required surface finishes, and it does so about three times faster,” said Mort. “Whatever the amount of time it takes for hand polishing a part, the Studer CT960 can produce the same surface finish three times faster. We simply give those parts coming off the Studer CT960 a quick buffing and they are ready to ship.”

Glenn Bridgman (left) discusses programming the shop’s Studer CT960 with Pat O’Halloran, CNC rogrammer/operator, at Bridge Tool & Die.

For Patrick O’Halloran, CNC programmer and operator of the Studer CT960 at Bridge Tool & Die, the learning curve for the machine was made easier thanks to United Grinding’s nearby Miamisburg, OH headquarters. “We did training at United Grinding, then they came to the shop for even more training and to help us further optimize our processes,” he said. “This allowed us to take full advantage of the machine’s capabilities, some of which we have yet to even use. But we are quickly progressing and continue to do more and more with the machine.”

Unlike its customers, Bridge Tool & Die’s high-mix/low-volume production schedule averages about 300 jobs per month. Lot sizes range from a single piece to blanket orders of 30 parts per month. Over 80% of the shop’s customers place recurring orders.

“We build special relationships with our customers, mainly because we are all involved with carbide in some way, and they know that there are few shops that specialize in the material, especially grinding it,” explained Bridgman.

Most carbide inserts are shrink-fit into mating steel casings. Doing so is cost-effective for customers because only the high wear sections are carbide rather than the entire component. Smaller parts are often made completely from carbide. Almost all parts require mirror surface finishes of between 2 to 4 µm.

The shop does all necessary operations for its customers’ parts. It turns the steel cases, grinds the carbide and assembles the two portions for a finished component. Part tolerances are typically around ±0.0002″ (0.005 mm), and some are as tight as ±0.0001″ (0.003 mm).

In addition to adopting advanced grinding technology like the Studer CT960, Bridge Tool & Die has arranged grinding cells, or work centers, on its shop floor. These cells have several machines in close proximity, which allows one operator to run multiple machines.

“Having these work stations with fully automatic, semi-automatic and manual machines has allowed us to keep pace with demand using the people we have because it’s tough to find good help these days,” said Bridgman. “We have to be as productive as possible with what we have.”

Glenn Bridgman, president (center right), Contessa Spaulding, account coordinator (center), and Greg Mort, business manager, along with the rest of the team at Bridge Tool & Die, with the shop’s new Studer CT960 grinding machine. Photo courtesy Dwight Cendrowski

The company has expanded its processing capabilities to include steel milling and turning operations with the acquisition three years ago of a general machining shop. Acquiring the shop across the street, formerly known as American Mold, has allowed Bridge Tool & Die to diversify into the injection mold machining arena. The new space also gives them room to grow. At the second shop, Bridge is now machining tool steel components for dies and molds, mainly for plastic injection molds and aluminum extrusions.

An expansion into other machining operations has helped increase business, especially from existing customers. In addition to grinding, customers are now asking Bridge Tool & Die to do conventional milling—work the shop would have previously farmed out. In the midst of the current business boom, the shop already has its new Studer CT960, as well as its manual operations, practically maxed out in terms of capacity. And Bridgman already has his sights set on increased CNC grinding capacity.

For more information from United Grinding, go to, or phone 937-859-1975.

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