AN6 (3/8-24) bolt tightened to 75% of bolt proof strength.
Camping force: 5,788 pounds. Required torque:
Cadmium plated and dry 28.9 lb Ft.
Moly anti-seize 19.9 Lb Ft.
The same amount of torque produces more (or less) bolt tension if the thread friction is reduced (or increased).
Great caution should be exercised if you use thread lubricants other than what the manufacture specifies. Thread lubricants change the friction between the threads, and between the nut and bolt face and the flange. This results in the bolt being over-tightened if thread friction is lowered, and under-tightened if thread friction is increased. The chart shows how different types of thread lubricants change torque requirements.
Some types of thread lubricants are more slippery than others. Generally, anti-seize that contains Moly (molybdenum disulfide - that black stuff) has the lowest thread friction (K factor of .11).
Moly-50 anti-seize is used to lubricate extremely heavy loaded splines and drive shafts in large aircraft. It is rated up to 500,000 psi. It is not to be used on roller element bearings, and due to its low friction, is generally not recommended for threaded fasteners.
Cold welding of stainless steel or galling can be prevented by using a nickle based anti-seize. Also, for threaded stainless steel bolts, reduce your speed driver speed. Speed creates heat and friction.
Generally, bare stainless steel threads should not be assembled dry. Even a slight amount of oil helps prevent galling. Stainless steel against aluminum (galvanic corrosion of aluminum potential), investigate using a primer between the surfaces or a zinc based anti-seize. Some large aerospace manufacturers specify silver coating to their stainless fastener threads (except in the fuel tanks!).
Anti-Seize products shown here can be purchased from Sacramento Sky Ranch Inc. 800-433-3564 or www.sacskyranch.com
Aircraft spark plugs use a graphite and water based anti-seize. Torque settings are based on using this anti-seize. Changing anti-seize to a different type presents two problems:
1. Anti-seize is non-metallic to prevent any metal particles from entering the combustion chamber and causing pre-ignition. So you are limited to a non-metallic anti-seize such as Moly, or Mica.
2. What torque do you use with the different anti-seize?
Using a different type of anti-seize changes the thread friction. The same amount of torque used before might now be too much or too little. Anti-Seize manufacturers will often publish a "K" factor or friction factor. The idea here is you can compare the thread friction "K" factor of graphite/water with your new anti-seize and compute the new torque value. Its best to just use the called for anti-seize and avoid problems.
Champion spark plug anti-seize for aircraft spark plugs.
Mechanic's Toolbox - Software for the Mechanic
40 software programs written especially for the mechanic
Mechanic's Toolbox includes: Anti-Seize Selector, Torque Wrench Calculator, and Bolt Strength Calculator. Compute torque from bolt strength, clamping force, breaking strength, shear strength. Includes strength charts,torque wrench extension calculations, torque conversion charts, standard torques for most nuts, bolts and screws, K factors, torque accuracy. etc.