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:

Frame Size	Mounting Bolt Size	Recommended Torque (Dry)
80-90	M8	25 Nm
100-132	M10	49 Nm
160-180	M12	85 Nm
200-225	M16	210 Nm
250-280	M20	410 Nm
315-355	M24	710 Nm

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.

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