VNIIMETMASH has developed special gear rolling mills, which are used for hot forming teeth of large-size module gears and sprockets for chain drive by means of cross-rolling.

VNIIMETMASH has developed two technological processes for gear rolling: tooth rolling with the allowance for grinding and for finishing gear-tooth milling, the first process (with the allowance for grinding - 0, 15... 0, 25 mm per tooth side) is used for rolling toothed gears (m = 2, 5... 5 mm) from blanks machined around faces, outer diameter and hole.

Large-size module gears (m = 6... 10 mm) rolling with the allowance for finishing gear-tooth milling is carried out directly from a stamped blank.

According to this method the rolling includes two operations: spinning in smooth rolls providing the required sizes around the diameter and width of toothing and rolling of spinned blank teeth in toothed rolls.

The above-mentioned process replaces two machining operations: turning of a forging around the outside diameter and faces and preliminary gear-tooth milling.

Subsequently rolled toothed gears are subjected to finishing gear-tooth milling.

The value of the allowance around the tooth contour is (0, 15... 0, 2) m, mm.

The rolled teeth are characterized by more favorable metal structure, when material fibres are parallel to the working surface of the tooth. When conventional technological process for manufacturing teeth is used, material fibers are concentric to the outer surface of the blank and are cut off during gear-tooth milling.

Bench tests and results of commercial operation demonstrate that strength and wear resistance of rolled toothed gear are 15... 30% higher as compared to toothed gears produced by milling.

Besides strength increase, tooth rolling process provides an increase of labor productivity and metal saving equal to 10... 20% of the blank mass.

Gear rolling mills ZPS-120, ZPS-350-2M, ZPS-800 and ZPS-1250-M designed by VNIIMETMASH are intended for rolling toothed gears 60 - 1000 mm in diameter and widely used at automobile and tractor works.