To avoid counterfeits, check bolts for grade and manufacturer. Photo: Firestone of Lisle (Ill.)
If manuals give torque values for oiled threads; follow instructions and, whenever possible, apply torque to the nut and not the bolt head. If you must torque the bolt head while holding the nut stationary, increase recommended torque by 20%.
When using lubricated nuts, lower dry torque recommendations by:
- 40% with anti-seize compounds
- 30% with heavy oil or graphite
- 25% with synthetic white grease or white lead, and Loc-Tite compounds
- 20% to 25% with light oil.
Don't reuse fasteners. We've all kept used fasteners that still look good. But using them in any high-strength application is false economy because they have less clamping force.
Store properly. Keep fasteners in boxes or bags in the shop. If you must travel, carry fasteners in blister packs or vacuum-sealed cards. They protect threads and prevent corrosion and physical damage.
Buyer BewareThey may look new, feel new, and fit like new, but “will fit” parts won't perform like new.
In the last 18 months, non-spec—or counterfeit—parts have again emerged, and fasteners are no exception.
Their offshore manufacturers cut corners or don't adhere to proper specifications. Often made from mild steel, with coatings that fail to protect from corrosion, these substandard parts typically have short life spans.
In the United States, fasteners are made to standards established by the Society of Automotive Engineers, the American Society of Mechanical Engineers, and American Society for Testing and Materials. Lines on the bolt or nut head pointing to the corners of the hex-head identify grades. Three radiating lines point to every other corner for Grade 5, and six point to each corner for Grade 8. Both are tough and able to resist strong lateral forces. A letter or symbol identifies the manufacturer.
Counterfeit bolts are made to lesser standards. Known counterfeits identified by the National Highway Traffic Safety Administration include those marked FM, H, KS, M, MS, NF, RT, or by the lack of a manufacturer's symbol.
The best way to avoid buying counterfeits is to know your source. Beyond that, examine parts against those being replaced.
For instance, substandard parts may weigh less due to weaker materials or thin construction. Often all counterfeit parts in a lot will have the same serial number stamped on them.
But basically, if a deal seems too good to be true, there's a great chance it's counterfeit.
— Paul Abelson is a former director of the Technology and Maintenance Council of the American Trucking Associations, a board member of Truck Writers of North America, and active in the Society of Automotive Engineers.