Grade 8 shear strength (6 Viewers)

[Nutz]

Looking for confirmation that I understand this right. Shear strength of a grade 8 bolt in good condition is 91,000 psi. So if I have a 5/8 bolt it would be:

91000/Pi*5/8^2 = 74,153 lbs before my 5/8 bolt would shear.

 

[2mbb]

No. your math is wrong.

1. The units for the shear strength is pounds force per square inch. To get pounds force, you need to multiply the shear strength by the shear area. Your equation implies you divided by the shear area.

2. The formula for the area of a circle is A = Pi * R^2, where R is the radius. The radius of a 5/8 diameter bolt is 5/16 inch.

Therefore the equation should be:

91000*Pi*(5/16)^2 = 27000 pounds force.

 

[Mace]

BTW, the shear strength varies between coarse and fine spline threads...

 

[REZARF]

BTW, everyone over builds on cruisers

 

[IBCRUSN]

For your reading pleasure

http://www.rockcrawler.com/techreports/fasteners/index.asp

http://www.pirate4x4.com/tech/billavista/NutsandBolts/index.html

Mace,

Where did you find info on the strength difference between cousre and fine thread? I could understand the difference between the two in tension but not in a sheer situation if using the correct length bolt (i.e. shank in sheer not the threaded section). Fill us in.

 

[Junk]

Site with some great info -> Boltscience.com

 

[Mace]

For your reading pleasure

http://www.rockcrawler.com/techreports/fasteners/index.asp

http://www.pirate4x4.com/tech/billavista/NutsandBolts/index.html

Mace,

Where did you find info on the strength difference between cousre and fine thread? I could understand the difference between the two in tension but not in a sheer situation if using the correct length bolt (i.e. shank in sheer not the threaded section). Fill us in.

How often is the "proper" length bolt used in our applications? most of the time you do have to use the threaded shear strength. Course, if you are having problems shearing grade 8 bolts you are doing something wrong


REZARF has it right

 

[IBCRUSN]

How often is the "proper" length bolt used in our applications? most of the time you do have to use the threaded shear strength.

You are correct, most folks don't think about that when assembling their project.

quote=Mace;2378333]Course, if you are having problems shearing grade 8 bolts you are doing something wrong [/quote]

That would be the time to access WTF your doing wrong.