Technical Information & Torque Specifications

All of our bolts are made with aircraft grade Titanium Alloy. One of the outstanding benefits of Mettec bolts is that we forge the heads for superior strength. The threads are then rolled to produce greater fatigue strength and reduce galling.

Our bolts exceed minimum Ultimate Tensile Strength (UTS) of 120,000 psi. Mettec can also make titanium bolts that exceed 160,000 psi in Ultimate Tensile Strength (UTS). Both styles of bolts conform to DIN and ASTM specifications. Titanium bolts can replace both grade 5 and grade 8 steel bolts which have minimum UTS requirements of 120,000 psi and 150,000 psi respectively. Metric bolts with an 8.8 rating can be replaced with titanium while bolts with a 10.9 rating can sometimes be replaced with titanium depending on intended use. Any bolts with a rating over 10.9 rating should not be replaced with titanium.

Torque Accuracy on Fasteners

Screw threads appear to be a simple concept yet much confusion and inconsistency exist regarding torque values. The mechanics of the screw thread are actually very complex and have numerous interacting variables. Sliding friction is affected by materials (like steel or aluminum on titanium), surface roughness, bearing area, material hardness, lubrication and so on.

Accuracy: Tightening is not an accurate science, look at the preloading accuracy published in the "Machinery's Handbook, 25th Edition, page 1404"

Method Accuracy
By Feel +/- 35%
Torque Wrench +/- 25%
Turn-of-nut +/- 15%
Preload washers +/- 10%
Bolt elongation +/- 3%
Strain gauges +/- 1%
Recommended Torque Spec's for Titanium Fasteners

Use torque values specified by your equipment manufacturer, when available. For titanium fasteners the torque values are listed below. We recommend anti-seize or moly paste be applied to the threads. If you have a specified torque value outside the Mettec range give us a call so that we may be able to more clearly understand your application and provide specific solutions for the use of titanium in your assembly.

The importance of correct application cannot be overemphasized. Under torquing can result in unnecessary wear of nuts and bolts as well as the parts they hold together. When insufficient pressures are applied, uneven loads will be transmitted throughout the assembly which may result in excessive wear or premature failure due to fatigue. Over torquing can be equally damaging because of failure of the bolt or nut from overstressing the thread areas.

Torque Limits for American Size Bolts in Tension

(For bolts in shear reduce the values shown below by 30-40%)

Non-lubricated Lubricated
Torque Torque Torque Torque
Bolt Size Min. Max. Bolt Size Min. Max.
5/16-18 80 in lbs 90 in lbs 5/16-18 72 in lbs 81 in lbs
3/8-16 160 in lbs 185 in lbs 3/8-16 144 in lbs 148 in lbs
3/8-24 200 in lbs 250 in lbs 3/8-24 180 in lbs 225 in lbs
7/16-14 235 in lbs 255 in lbs 7/16-14 211 in lbs 229 in lbs
7/16-20 520 in lbs 630 in lbs 7/16-20 468 in lbs 567 in lbs
1/2-13 400 in lbs 480 in lbs 1/2-13 360 in lbs 432 in lbs
1/2-20 770 in lbs 950 in lbs 1/2-20 693 in lbs 855 in lbs
Torque Limits for Metric Size Bolts in Tension

(For bolts in shear reduce the values shown below by 30-40%)

Non-lubricated Lubricated
Torque Torque Torque Torque
Bolt Size Min. Max. Bolt Size Min. Max.
M6-1.00 80 in-lbs 100 in-lbs M6-1.00 72 in lbs 90 in-lbs
M8-1.25 120 in-lbs 145 in-lbs M8-1.25 108 in-lbs 130 in-lbs
M10-1.25 200 in-lbs 255 in-lbs M10-1.25 180 in-lbs 230 in-lbs
M10-1.5 160 in-lbs 185 in-lbs M10-1.5 144 in-lbs 148 in-lbs