Grade 8 Bolts are some of the most durable and reliable fasteners you can buy in the industrial world. Grad 8 Bolts are most useful in areas such as the military, aerospace or marine related mechanical applications where high stress and strong load bearing pressures are a major factor.
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What are Grade 8 Bolts?
Grade 8 Bolts also commonly known as hex head cap screws are proportioned and have tolerance to assure full and proper loading when assembled into a tapped hole. They are the highest strength of standard SAE inch series cap screws and are made from alloy steels. Grade 8 hex head bolts and grades achieve their strength from a quench and temper heat treatment. Their value is to torque applications such as steel beams, joints, chassis, etc. together to become one. A washer face is provided under the head to provide a bearing surface when tighten. There are several grades of bolts beginning with the least strong grade to the heaviest grade, Grade 2 (tensile strength 60,000 psi), Grade 5 (120,000 psi) and Grade 8 (150,000). These Grades can also be identified by dashes on grade 5 and 8s. Grade 5 has three slash marks, and Grade 8s have a manufacturer HD mark and six slash marks. No Grade identification is required for Grade 2. They all come in different lengths and diameters. It is important to know what grade platting to use for the job.
What platting of Grade 8 bolts are there?
You can get Grade 8 bolts in a plain finish (black) or zinc plated. Both are equally strong in the standard mechanical test specifications world. Other platting(s) can be special ordered.
How are the Grade 8 bolts used?
Grade 8 bolts work by turning or twisting to the right for fastening two separate flat pieces of wood, metal, bases or joints together. The end of cap screws is chamfered to aid in inserting into a tapped hole. Grade 8 bolts are cold formed on precision high-speed formers, utilizing in-process quality systems which have full traceability from raw material to each box of fasteners. Cap screws can be used in tapped holes or with a nut.
Most designs with cap screws where a clamp load is needed require the cap screw to be tightened to 75% of the proof load for a safe working range. Shear strength of a cap screw loaded in single shear through the threads is about 60% of the ultimate tensile strength, so working loads should be lower than this breaking strength. The fatigue of cap screws as measured by endurance limit will vary widely depending upon the amplitude, frequency, and type of applied load. Endurance limits of 10-20% of the tensile strength have been reported for high strength cap screws.
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