It’s not a household name, but Setco in Delhi Township has stayed in business for nearly a century by concentrating on what it does best.

The company, which marks its 100th anniversary next year, is North America’s largest independent maker of machine tool spindles and slides, key components for machines that cut and form metal.

Setco, which employs about 90, annually builds or rebuilds more than 3,000 spindles, the rotating components used to hold and drive the cutting tools on lathes, milling machines and other machine tools.

Unlike other better-known local machine tool companies such as Mazak in Florence and MAG IAS in Hebron, Setco doesn’t make complete machines. Instead, it concentrates on spindles and slides, the components that move parts to the spindle or vice-versa.

That’s by design.

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“The company didn’t want to end up competing with our customers. So it focused on just spindles and slides,” says Jeff Clark, president of Setco, which is owned by Holden Industries Inc., a diversified, employee-owned manufacturer in Deerfield, Ill.

America’s machine tool industry has struggled over the past few decades as more and more manufacturing has moved offshore. But the recovery in U.S. manufacturing over the past year has put new life into the U.S. machine tool industry.

U.S. machine tool sales topped $1.9 billion through May, up 108 percent from the same period last year, according to the latest monthly report from a consortium of machine tool makers and suppliers.

Setco doesn’t disclose revenues, but it represents more than 10 percent of Holden Industries’ more than $200 million in annual revenues. Besides its plant here, Setco has sales and service centers in California, Michigan and Georgia.

Clark says Setco expects a 20 percent increase in sales and has added about 10 jobs this year. That’s a big change from just two years ago, when the company was forced to lay off workers and reduce hours because of the recession.

With the rebound in manufacturing, Setco is investing in new machinery and implementing lean-manufacturing techniques to improve efficiency and lower costs, said Scott Bubenhofer, manager of Setco’s 60,000-square-foot plant on Hillside Avenue.

As more of its manufacturing customers move offshore, Clark says Setco also is looking to expand through acquisitions both overseas and in the United States.

Founded in 1912 as Standard Electric Tool Co., the company initially made grinders used to finish iron casting for machine tools, but turned its expertise in making rotating parts into producing machine tool spindles about 50 years ago.

Over the years Setco has designed and built spindles for some of America’s best-known manufacturers, such as Boeing Co., General Motors and Ford Motor Co. It also has supplied hundreds of other smaller manufacturing and machine shops.

“We’re not a sexy company, but a lot of our big industrial customers count on us,” Clark says.

The nature of Setco’s customer base has changed. In the mid-1990s, three-fourths of its business was with automakers, compared with one-fourth today.

A decade ago, service and repair work made up less than a third of Setco’s business, but today represents about half its sales.

“The key is we’ve been able to adapt to changes in the marketplace,” Clark says.

Setco’s niche expertise in making and repairing spindles has made it a “go-to” source when a manufacturer has a problem.

“If you have multi-million-dollar machine tool, you can’t afford to let it sit idle because a spindle is broken,” Clark says.

Setco’s engineers are regularly sought out for advice by both users of its own spindles and competitors’ products, says Brian Schloemer, engineering manager.