Threaded Fasteners 00.04 General Instructions Fastener Replacement Do not use lockwashers and flatwashers in combina- tion (against each other); each defeats the other’s purpose. When replacing fasteners, use only identical bolts, washers, and nuts; they must be the same size, strength, and finish as originally specified. See the Freightliner Service Parts Catalog for fastener speci- fications. Use stainless steel fasteners against chrome plating, unpainted aluminum, or stainless steel. Fastener Tightening When replacing graded (or metric class) bolts and capscrews, use only fasteners that have the manu- facturer’s trademark or identification on the bolt head; do not use substandard bolts.
Inferior, counterfeit fas- teners are difficult to identify; buy your fasteners from a reputable supplier. Before installing fasteners, clean all fastener (and parts) threads, and all surfaces being clamped. To ensure they are always torqued accurately, Freightliner recommends that all fasteners be lubri- cated with oil (unless specifically instructed to install them dry), then torqued to the values for lubricated- and plated-thread fasteners. When locking compound or antiseize compound is recommended for a fas- tener, the compound acts as a lubricant, and oil is not needed. Fastener Selection and Installation When using nuts with bolts, use a grade (or class) of nut that matches the bolt.
Bring parts and fasteners into contact, with no gaps between them, before using a torque wrench to tighten fasteners to their final torque values. When installing non-flanged fasteners, use hardened steel flatwashers under the bolt (capscrew) head, and under the hexnut or locknut. Tighten the nut, not the bolt head. This will give a truer torque reading by eliminating bolt body friction. For bolts 4 inches (100 mm) or less in length, make sure that at least 1-1/2 threads and no more than 5/8-inch (16-mm) bolt length extends through the nut after it has been tightened. For bolts longer than 4 inches (100 mm), allow a minimum of 1-1/2 threads and a maximum of 3/4-inch (19-mm) bolt length.
Always use a torque wrench to tighten fasteners, and use a slow, smooth, even pull on the wrench. Do not overtorque fasteners; overtightening causes perma- nent stretching of the fasteners, which can result in breakage of the parts or fasteners. Never hammer or screw bolts into place. Align the holes of the parts being attached, so that the nut and bolt surfaces are flush against the washers, and the washers are flush against the parts. If specific torque values are not given for counter- sunk bolts, use the torque value for the correspond- ing size and grade of regular bolt, as given in Speci- fications, 400 .
When installing fasteners in aluminum or plastic parts with threaded holes, start the fasteners by hand, to ensure straight starting and to prevent damaged threads. Always follow the torque sequence or torque interval when provided, to ensure that clamping forces are even, and parts and fasteners are not distorted. Do not use lockwashers (split or toothed) next to alu- minum surfaces. Thread Locking Compound Application When installing studs that do not have an interfer- ence fit, install them with thread locking compound, as instructed in this subject.
When the use of thread locking compound is recom- mended or desired, for studs, capscrews, and bolts with a thread diameter of 1 inch (25 mm) or less, use Loctite ® 271 or Perma-Lok ® HM-128. When installing parts that are mounted on studs, use free-spinning (non-locking) nuts and helical-spring (split) lockwashers or internal-tooth lockwashers. Do not use locknuts, because they tend to loosen the studs during removal. Do not use plain washers (flat- washers). For thread diameters over 1 inch (25 mm), use Loc- tite 277. Business Class M2 Workshop Manual, Supplement 0, January 2002 100/1