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Forged Gear Blanks: Truly Time-Tested

by Jack McGuinn, Senior Editor

Ajax Rolled Ring

A forged rolled ring from Ajax Rolled Rings.

It has been said that clichés become clichés because they typically contain a kernel of everyday truth. One of the more common ones in manufacturing is "garbage in, garbage out"—and with good reason. In many ways, the process path to quality, cost-effective and profit-laden manufacturing begins at the receiving dock, where incoming materials—raw or otherwise—are inspected to ensure they meet agreed-upon specifications.

The gear industry is certainly no different. If on any given day what comes through your receiving area and OK'd by your quality team is later found to be wanting, various personnel will have some explaining to do.

Gear blanks, especially those intended for gears used in tight-tolerance, heavy-duty applications, are components that call out for extremely rigorous and vigilant inspection. And, there exist more than a few metal-forming processes for making blanks (more on that to follow). But arguably the oldest known metalworking process—forging—with its DNA linked way back to those smarty-pants Egyptian engineers—is our focus here.

We asked some suppliers for their take on the differences between forgings and, for example, castings—the two predominant processes for producing metal gear blanks.

Weighing in with a response—but necessarily wishing to remain anonymous—a vice president of sales for a Midwest-based forger says "The main advantage of a forged gear is that, due to the mechanical hot-working of the piece, the part will have higher inherent strength and cleanliness levels."

What other inherent advantages exist in forging over other metal-forming processes for manufacturing gear blanks? According to www.forging.org:

Forging of gear blanks compared with:

Machined bar/plate:
Powder metal (P/M):
Reinforced plastics/composite (RP/C):

Metallurgy is indeed a complex, obscure science to most of us, which can perhaps make deciding on a supplier a bit tricky. But in reality the process is quite similar to choosing other vendors.

As for our mystery guest: "We believe that reliability and on-time delivery should play a key role in the decision making process. Quality is pretty much a given if you want to participate in the market long-term, and it costs our customers money on their bottom line when the suppliers are late."

Also responding is Bob Pancoast, sales and marketing for Ajax Rolled Ring & Machine in York, South Carolina: "Quality, on-time deliveries, price—in that order," are the criteria for choosing a blanks supplier.

One might reasonably wonder what level of sophistication is required of equipment operators at forging plants. Is, for example, gear design knowledge imperative for forgers of gear blanks?

"Gear design is not really of importance to forgers and casters" says Ajax's Pancoast. "The important thing is for the manufacturer of the gear blank to make the part to the metallurgical and dimensional requirements of the customer."

On the other hand, our Midwest-based forger believes that "Anytime a supplier can be more informed about their customer's products, the better the business relationship and opportunity to look for ways to add value to the customer's process. While that knowledge by itself doesn't win orders, the supplier does have to fully understand the specification requirements to ensure making something that will meet the intended design criteria. More knowledge of the customer's design can help facilitate more interaction and foster a long-term relationship. To that end, we have held forging seminars at some of our gear customers' locations to help them design better products." (Ed.'s Note: Have a case study, technical paper, etc., for us on any of the other gear blank processes mentioned here? We'd love to hear from you!)