Hardness of Grade 8 bolts?
Whoever wrote 58-62 HRC here originally was wrong. My thoughts and prayers are with the five people who found that useful. For 4140 steel (most commonly used for this grade), the hardness range would be 33-39 HRC. This puts it comfortably above the 150,000 psi min. tensile strength.
Grade 10.9 bolts or capscrews have a minimum tensile strength of 1040N/mm2 and a hardness of 320 - 380Hv10. Grade 12.9 bolts or capscrews have a minimum tensile strength of 1220N/mm2 and a hardness of 385 - 435Hv10. The 12.9 fastener is therefore a higher grade (hardness and tensile strength) fastener compared with 10.9 grade
SAE sets standard sizes and grades for bolts. Size and Grade are different: Size is set By the SAE (society of Automotive engineer's) and is stated as thickness followed by thread pitch followed by length 1/4 x 24 (threads per inch) x 1 1/14 (inches long) Grade Is a statement of strength and hardness. Most auto hardware tends to be grade 5 and some high strength stuff is grade 8 or grade 12
if your speaking of long one that goes through top/bottom it is 5/8 and about 12 to 13 inches long. but good luck replacing a broken one, I can't locate it either. Seems it is unheard of to be so long. mine rusted and broke now a month later still can't locate replacement. I recently had upper control arm bushings replaced and my mechanic noticed that the bolts you mention are rusted thru. I ended…
According to the Mohs scale of hardness, Diamond has a hardness of 10 and Quartz has a hardness of 7. Any mineral with a hardness greater than 7 can scratch quartz and diamond can scratch any mineral with a hardness less than 10. Corundum (hardness of 9) and Topaz (hardness of 8) are two examples of minerals that can scratch quartz but not diamond.