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(informal) the most important and practical details of something: Jim put together the nuts and bolts of the deal; I added the details. Nuts and bolts are small pieces of metal that are screwed together to fasten things together.
Both nuts and bolts come in many types. A nut is a small metallic piece of metal with a spiral cut groove that runs around a hole in its centre while a bolt is a metallic piece with a round stem as its body and threaded into one end. Bolts have different length sizes while nuts have a standard size.
Threaded fasteners, when installed and tightened, should protrude a distance of at least one thread beyond the top of the nut or plastic insert. Excessive protrusion should be avoided, particularly when necessary clearances, accessibility, and safety are important.
Symbol for identification of grade, i.e., B8M, applied to head. Manufacturer’s identification mark, e.g., X ( on head of bolts and screws and on one end of studs and stud bolts). Symbol for identification of grade, i.e., B8M, applied to head. Line stamped under B8M.
SAE J429 (Society of Automotive Engineers) bolts have radial lines, whereas ASTM (American Society for Testing and Materials) uses a combination of letters and numbers to indicate the grade. Three radial lines will indicate an SAE grade 5 fastener, while six radial lines will indicate an SAE grade 8 fastener.
The “M” designation for metric screws indicates the nominal outer diameter of the screw thread, in millimetres (e.g. an M6 screw has a nominal outer diameter of 6 millimetres).
Most bolts have a right-handed thread and turn in a clockwise direction as you screw them in. If you look at the threads of such a bolt, they appear to angle upward to the right (this is called pitch). Reverse-thread bolts have a left-handed thread and turn in a counter-clockwise direction when tightened.
Grade 8 bolts have been hardened more than grade 5 bolts. Thus they are stronger and are used in demanding applications such as automotive suspensions. Grade 8 bolts have 6 evenly spaced radial lines on the head. Grade G is roughly equivalent to Grade 8.
8.8- This type of grade is often referred to as the structural grade for bolts. When a bolt has a grading of S, it means that it can withstand a stress of 45 to 49.9 metric tonnes per 6.45 cm². This grading, which is typically stamped on the head of the bolt, has the same tensile strength as a grade 8.8 bolt.
The mechanical difference between the 12.9 and 8.8 is yield strength (roughly 90% of 1200 MPa vs 80% of 800 MPa). That means the 12.9 can be stretched further (i.e. torqued to some higher value) before it yields, which of course increases the clamp force.
grade 8
Bolt Grade Markings and Strength ChartGrade and MaterialMechanical PropertiesMin. Tensile Strength (psi)Class 8.8 Medium carbon steel, quenched and tempered800830Class 10.9 Alloy steel, quenched and tempered104018
BUMAX® Ultra has proven itself as the world’s strongest bolt – in various highly-demanding critical fastener applications around the world where standard fasteners are simply inadequate.
Many fasteners (screws, etc.), especially smaller sizes, are typically not graded—their strength isn’t specified….Table 1.Grade/ClassStrengthMetric Class 8.8Similar to Grade 5.Metric Class 10.9Similar to Grade 8.Metric Class 12.9The highest metric class for strength, it exceeds Grade 8.11
12.9 grade steel has 120% of the tensile strength of 10.9 grade steel. The “12” prefix indicates a tensile strength of X100 N/mm^2 and the “9” suffix indicates a multiplier. Both 12.9 and 10.9 have the same multiplier, so the comparison is straightforward: 12 to 10.
The minimum ultimate tensile strength of the Grade 12.9 Metric Hex Head Bolts is about 1242 Mpa or 180,000 PSI, making them the highest grade of bolts produced.In fact, the Grade 12.9 Nuts is known for their high tensile strength.
Used in automotive applications and for bolting large and forged parts, metric 10.9 bolts exhibit high tensile strength and good wear resistance. The yield strength of the bolts is 940 and the tensile strength is 1040 MPa.
One common misconception about bolts is that a higher rated bolt is stronger, yet more brittle, and therefore lower grades should be used in places like in suspension systems so they can deform rather then break. This is wrong! There are two types of forces a bolt experiences, tension and shear.
There are several grades of bolts but the three common grades for SAE are 2, 5 and 8. No matter the system used to grade the bolts, the higher the number means the stronger the bolt. For most home and automotive applications, you won’t need anything more than a grade 8 bolt strength or metric class 10.9.
In actual fact, Grade 5 bolts are often preferred over Grade 8 . A Grade 8 has a very high tensile strength, but can be brittle. In applications such as suspensions, a very high number of load/unload cycles can produce work hardening, which produces an immediate, or catastrophic failure.