Home |
Search |
Today's Posts |
|
Home Repair (alt.home.repair) For all homeowners and DIYers with many experienced tradesmen. Solve your toughest home fix-it problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to alt.home.repair
|
|||
|
|||
What grade is this bolt?
People refer to the hardened bolts as grade 8.
What grade are the standard bolts, and what does "grade" mean? I know it has to do with hardness, but exactly how much more hard is a grade? |
#2
Posted to alt.home.repair
|
|||
|
|||
What grade is this bolt?
People refer to the hardened bolts as grade 8.
What grade are the standard bolts, and what does "grade" mean? I know it has to do with hardness, but exactly how much more hard is a grade? There is no "standard". Perhaps you mean "no mark", which could mean an SAE Grade 1 bolt (33 Kpsi proof strength) or could be just an ungraded cheap import that is much weaker. The grade is all about the tensile strength of the material, not the hardness (although harder usually means stronger). Proof strengths run from SAE grade 1 at 33 Kpsi, 2 at 55, 4 at 65, 5 at 85, 7 at 105, and 8 at 120. Not sure what happened to grades 3 and 6. The proof strength is determined by the carbon content and (in grades 6 and up) alloy content of the steel. To figure the actual strength of a bolt in pounds, you multiply the cross sectional area of the minor diameter in inches times the proof strength of the material in psi. So a grade 8 1/2-13 UNC bolt, having a minor diameter of 0.407 inches, has pi*(0.407/2)^2 * 120,000 ~= 15,000 lbs proof strength; grade 1 would be 4300 lbs. The common "B" mark on the bolt head (three ticks at 12/4/8 o'clock) indicates SAE grade 5, and the "I" mark (six ticks at 12/2/4/6/8/10 o'clock) grade 8. The Handbook has a dozen different such marks for various SAE and ASTM grades. A higher grade bolt is not necessarily better. Besides cost, if you ever have to drill it out, you want the lowest grade bolt that holds up to the application. "Bolts, screws, and other fasteners are marked on the head with a symbol that identifies the grade of the fastener. The grade specification establishes the minimum mechanical properties that the fastener must meet." -- Machinery's Handbook, 26th ed., p 1488 |
#3
Posted to alt.home.repair
|
|||
|
|||
What grade is this bolt?
Richard J Kinch wrote: People refer to the hardened bolts as grade 8. What grade are the standard bolts, and what does "grade" mean? I know it has to do with hardness, but exactly how much more hard is a grade? There is no "standard". Perhaps you mean "no mark", which could mean an SAE Grade 1 bolt (33 Kpsi proof strength) or could be just an ungraded cheap import that is much weaker. The grade is all about the tensile strength of the material, not the hardness (although harder usually means stronger). Proof strengths run from SAE grade 1 at 33 Kpsi, 2 at 55, 4 at 65, 5 at 85, 7 at 105, and 8 at 120. Not sure what happened to grades 3 and 6. The proof strength is determined by the carbon content and (in grades 6 and up) alloy content of the steel. To figure the actual strength of a bolt in pounds, you multiply the cross sectional area of the minor diameter in inches times the proof strength of the material in psi. So a grade 8 1/2-13 UNC bolt, having a minor diameter of 0.407 inches, has pi*(0.407/2)^2 * 120,000 ~= 15,000 lbs proof strength; grade 1 would be 4300 lbs. The common "B" mark on the bolt head (three ticks at 12/4/8 o'clock) indicates SAE grade 5, and the "I" mark (six ticks at 12/2/4/6/8/10 o'clock) grade 8. The Handbook has a dozen different such marks for various SAE and ASTM grades. A higher grade bolt is not necessarily better. Besides cost, if you ever have to drill it out, you want the lowest grade bolt that holds up to the application. "Bolts, screws, and other fasteners are marked on the head with a symbol that identifies the grade of the fastener. The grade specification establishes the minimum mechanical properties that the fastener must meet." -- Machinery's Handbook, 26th ed., p 1488 Thanks R.K. That's a keeper. TB |
#4
Posted to alt.home.repair
|
|||
|
|||
What grade is this bolt?
Richard J Kinch wrote:
What grade are the standard bolts, and what does "grade" mean? There is no "standard". Perhaps you mean "no mark", which could mean an SAE Grade 1 bolt (33 Kpsi proof strength) or could be just an ungraded cheap import that is much weaker. The grade is all about the tensile strength of the material, not the hardness (although harder usually means stronger). Proof strengths run from SAE grade 1 at 33 Kpsi, 2 at 55, 4 at 65, 5 at 85, 7 at 105, and 8 at 120... Nice answer :-) Looks like we add about 20K psi per grade. To figure the actual strength of a bolt in pounds, you multiply the cross sectional area of the minor diameter in inches times the proof strength of the material in psi. So a grade 8 1/2-13 UNC bolt, having a minor diameter of 0.407 inches, has pi*(0.407/2)^2 * 120,000 ~= 15,000 lbs proof strength; grade 1 would be 4300 lbs. Hmmm. I woulda thunk the bolt would fail when the threads slip, eg when the force exceeds the area of the ring between minor and major diameters times the tensile strength. So if that bolt had a 0.427" major diameter, it might fail at Pi((0.427/2)^2-(0.407/2)^2)120K = 1572 pounds, but maybe that isn't true, if the nut is thick enough. Nick |
#5
Posted to alt.home.repair
|
|||
|
|||
What grade is this bolt?
wrote in message Hmmm. I woulda thunk the bolt would fail when the threads slip, eg when the force exceeds the area of the ring between minor and major diameters times the tensile strength. So if that bolt had a 0.427" major diameter, it might fail at Pi((0.427/2)^2-(0.407/2)^2)120K = 1572 pounds, but maybe that isn't true, if the nut is thick enough. Not every bolt uses a nut. |
#6
Posted to alt.home.repair
|
|||
|
|||
What grade is this bolt?
|
#7
Posted to alt.home.repair
|
|||
|
|||
What grade is this bolt?
|
#8
Posted to alt.home.repair
|
|||
|
|||
What grade is this bolt?
regardless of grade it goes back to acheiving the correct torque on a bolt
to max out its strength or they are subject to backing out or loosening up, nut or no nut "Edwin Pawlowski" wrote in message news wrote in message Hmmm. I woulda thunk the bolt would fail when the threads slip, eg when the force exceeds the area of the ring between minor and major diameters times the tensile strength. So if that bolt had a 0.427" major diameter, it might fail at Pi((0.427/2)^2-(0.407/2)^2)120K = 1572 pounds, but maybe that isn't true, if the nut is thick enough. Not every bolt uses a nut. |
#9
Posted to alt.home.repair
|
|||
|
|||
What grade is this bolt?
On Sun, 09 Jul 2006 04:02:07 -0500, with neither quill nor qualm,
quickly quoth: People refer to the hardened bolts as grade 8. What grade are the standard bolts, and what does "grade" mean? I know it has to do with hardness, but exactly how much more hard is a grade? http://www.americanfastener.com/tech...ings_steel.asp Grade 5 is about 3 times stronger than an unmarked bolt. Grade 8 is about 4 times stronger @ 130kpsi. http://www.boltdepot.com/fastener-in...Materials.aspx -- When love and skill work together, expect a miracle. --John Ruskin (1819-1900) |
#10
Posted to alt.home.repair
|
|||
|
|||
What grade is this bolt?
bob kater wrote:
regardless of grade it goes back to acheiving the correct torque on a bolt to max out its strength... Hmmm. That might double this Pi((0.427/2)^2-(0.407/2)^2)120K = 1572 pounds. Nick |
#11
Posted to alt.home.repair
|
|||
|
|||
What grade is this bolt?
|
#12
Posted to alt.home.repair
|
|||
|
|||
What grade is this bolt?
I woulda thunk the bolt would fail when the threads slip, eg when
the force exceeds the area of the ring between minor and major diameters times the tensile strength. Thread failure is a possible failure mode, but that depends on the length of thread engagement. Typically enough threads are engaged that the shank pulls apart before the threads pull out. The Handbook tells you how to analyze and calculate all that. |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Damaged 8mm bolt hole... Best repair? | Home Repair | |||
harbor freight tools - chinese army owned? | Metalworking | |||
Bolt Hole Circles on Acu-Rite DRO | Metalworking | |||
question replacing subfloor in bathroom, has a support bolt in the middle of it | Home Repair | |||
Removing a Frozen Bolt with Heat | Home Repair |