Determining sheer tonnage

Q: What is the formula for determining sheer tonnage?

A: As a general rule, the tonnage is about 60-65% of the ultimate strength of the steel being cut. For example, if it is a 1035 steel and has ultimate strength of 120 ksi (60 tpsi), then the shear tonnage for a 4-in.-square bar is 16 in. 2 times 36 to 39 tons, or 600 to 625 tons to shear the bar. This is for a partially supported bar (behind the shear blade).

There are ways to reduce the tonnages via a "knick break" system but this can lead to excessive bar end distortions. For elongated forgings this is not a problem, but for upst forging or for short billets, this alternative is not good.

I recommend that you contact Ajax for data on shear tonnages various cross corner, round, and squarecut shear cuts. As I recall, they have tables for their bar shears.

H. James Henning answers forgers' technical and operational questions. For more than 40 years he held key technical positions in the forging industry, most recently as director of technology for the Forging Industry Association. He is president of Henning Education Services, Columbus, OH, specializing in customized education and training in forging technologies.

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