Hobson tightening torque chart
Nyloc Nut Torque Chart and Prevailing Torque Lock Nuts: Technical Guide
Hobson's two-page technical document on Nyloc and other prevailing torque lock nuts. Page one tabulates basic dimensions, maximum prevailing torque, clamp load and installation torque for metric property class 6 Nyloc nuts, M5 to M39; page two explains how to tighten, re-use and expose these nuts.
What this covers
- Nyloc nut dimensions
- Prevailing torque and clamp load
- Installation torque
- Installing prevailing torque nuts
- Re-use
- Nylon exposure
For Nyloc Nut.
Key things to remember
The essentials from this document in plain words. Check the full document before you rely on a figure.
- Installation torque, property class 6 coarse thread, M10: 17.1Nm zinc plated, 34.9Nm mechanically galvanised; M12: 28.5Nm and 59.5Nm. These give a clamp load of 65% of proof stress for a property class 4.6 bolt, using nut factors 0.14 (zinc) and 0.35 (mechanical galvanised).
- The torques are a guide only, based on the first tightening of a single assembly in isolation. Zinc plated covers both zinc yellow and clear zinc.
- Do not use standard torque values on a prevailing torque nut: the extra torque to turn the nut on the thread lowers the clamp load. Add the prevailing torque to the target torque (T = F x k x d + TFV).
- The nut needs full threads right through the locking element, with at least one full thread protruding from the nut.
- They can be re-used, but every use reduces their grip: check the prevailing torque with a torque wrench before re-use.
- Extreme sun and salt can damage the nylon insert. Nylocs that have had long or extreme exposure still hold, but should not be re-used. With a steel coating that suits the environment, they suit outdoor and marine use.
Who it helps: Mechanics and fabricators setting torque on Nyloc and other lock nuts.
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This document is published by Hobson Engineering, who supply this range to us. We show it here in full so you can read it next to the product; the summary above is ours. Read it on this page or download the PDF. For the most current version, ask us.