The piercing mill is used to pierce out and roll the mother tube out of original billet. The single input, double output, two-stage gearbox drives this mill. This is a three metre tall and robust gearbox with a base of 2.8/1.4 meters and weighing around 18 tons.

Technical specifications :

• Input power : 1250 kW @ 750 rpm, A.C.motor
• Reduction ratio : 5.6875:1
• Axial thrust : 1,80,000 N on each output shaft

The gears are made from high tensile carburizing alloy steel, 17 CrNiMo6 as per DIN 17210, case hardened to 60± 2HRc and finely ground to accuracy Class 6 as per the DIN standard to give smooth and trouble free operation. Output shafts are made from medium carbon steel CK 60N as per DIN 17200 of adequate size to withstand heavy load transmission for better rigidity without undue deflection. Gears are integral with shaft/key fitted to shaft and are supported in antifriction spherical roller bearings of adequate size to give higher working life and to correct misalignment. Output shafts are also provided with spherical thrust bearings to tolerate axial thrust load in both the directions. Gears and bearings are housed in accurately machined and highly rigid/robust MS fabricated housing to give better performance against severe jerks and vibrations.

Separate motor driven lubricating system is provided to enhance cooling and lubrication of bearings and gear meshings.