Cast Iron AC Induction Motors – Mounting Bolt Torque Guidance

The correct tightening torque depends on the motor frame size and the corresponding foot mounting bolt. Below is a general guideline based on typical ISO metric bolts used in our cast iron range:

• Torque values are based on ISO grade 8.8 bolts with dry (unlubricated) threads. For lubricated threads, reduce torque by approximately 15–20%.
• Flat washers are recommended to distribute load and prevent paint damage to motor feet.
• Always ensure the mounting surface is flat and clean to avoid distortion during tightening.
• For flange-mounted motors (e.g. B5), refer to flange mounting torque specifications.
• Use of torque-controlled tools is advised. Avoid overtightening with impact drivers.
• Bolt sizes may vary slightly depending on customer specification—refer to the motor’s dimensional drawing for exact details.