Engineers in the US have created a 19m-diameter gear assembly that weighs 54.8 tonnes. The team, from the machining specialist Mag Fond du Lac, used a horizontal boring mill and specially designed tools to cut the 588 teeth in the gear which is going to be used in a bridge project.

The two-piece gear assembly consists of a 24-section track, which serves as the base, and a 12-section upper gear rack. The gear was assembled to a pitch diameter concentricity of 0.8mm.

“We cut the gear teeth on an unconventional machine,” reports project manager, Mark Huhn. “In most cases, the tooth involute would be generated by the machine itself, but we used a tool with the involute built into the cutter, which was accomplished by grinding the tooth form into the cutter first.”