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TimkenSteel alters steel to lower machining costs for automakers

Bottom line: instead of making a better broaching tool, we set out to make steel that was easier to cut, but just as strong.

Broaching is a machining technique commonly used to cut gear teeth or cam profiles for the high-volume manufacture of power transmission parts used in vehicles.

The part tooth profiles can be formed in a single machining operation with minimal overall time, making it ideal for cost-sensitive applications.  However, in order to accomplish the broaching operation in a single station and operation, the broach machine must perform the entire roughing, shaping and finishing of the desired part profile in one step using a long, multi-piece, high-speed steel broach tool. 

The broach tool is relatively expensive to manufacture and can only be redressed or sharpened a finite number of times before the tool is no longer usable.  The precise broaching and tooling cost per manufactured part is highly dependent upon the number of parts that can be manufactured between each broach tool redressing.

With tooling and redressing costs over the life of a helical broach bar on the order of $50,000 to $100,000, and total parts manufactured on a single broach bar currently in the range of 10,000 to 80,000 parts, the cost to broach a part is typically in the range of $0.60 to $5.00.  Hence, the broach tooling cost represents around 15 to 50 percent of the total manufacturing cost for a finished part. 

Reduction of broaching costs is normally accomplished through developments of tooling materials, coatings, lubricants, and processing parameters without as much attention given to the influence of the material condition of the part being broached. To study the influence of steel material condition on broach tooling life, TimkenSteel developed a laboratory broach test machine to perform numerous studies on the broaching characteristics of various steel grades and metallurgical conditions.

The test unit enables the quantitative measurement of broach tool wear characteristics resulting from repeated broach operations for each of the input steel grades and conditions. The machine development and subsequent testing performed on the various material conditions resulted in a more thorough understanding of the metallurgical variables affecting broach tool life and subsequent part manufacturing costs.

To learn more, watch a video on how we reduced broaching costs, or read Mike’s “Improved Broaching Steel Technology” paper.

Mike Burnett is a technologist at TimkenSteel and has been with the company for more than 30 years. Mike earned a bachelor’s degree in metallurgical engineering at Purdue University and a master’s in metallurgical engineering at Colorado School of Mines. The American Iron and Steel Institute awarded him a finalist medal earlier this year for his “Improved Broaching Steel Technology” paper.