Grade 8 Bolts: sheer strength in a 5/8 size.

[DougMH]

Hello,

I am trying to figure out if the grade 8 bolts in my suspension setup have a determined sheer strength. I want to determine what type of suspension loading could occur before I sheer off the bolts.

I have a feeling that under no circumstances will I be able to sheer these bolts... but I just want to be sure.

If any one had a link to a table of sheer strengths... or maybe some info, that would be great. I searched and only found tensile strength on most of the web.

 

[CoryPad]

Most fastener material and product specifications do not list shear strength requirements. For quenched and tempered steels (including Grade 8), the ultimate shear strength has been found to be about 0.62 times the ultimate tensile strength.

 

[DougMH]

Thanks alot. That is a big help.

 

[winny]

The ultimate strength, Fu of Grade 8.8 bolts are 800 MPa and its shear strength, Fv is 145 MPa when threads are on the shear plane and 210 MPa when the treads are exccluded from the shear plane.

For Diameter 5/8" (16mm) Shear strength is 30 kN when threads are included in the shear plane and 40 kN when treads are excluded from the shear plane.

I,m using Allowable Stresses here.

Hope it helps.

 

[CoryPad]

winny,

Grade 8 refers to parts made according to standards like SAE J 429, Mechanical and Material Requirements for Externally Threaded Fasteners, or ASTM A490, Standard Specification for Structural Bolts, Alloy Steel, Heat Treated, 150 ksi Minimum Tensile Strength, which use inch-pound units. Grade 8 is similar to Property Class 10.9 according to ISO 898-1, Mechanical properties of fasteners made of carbon steel and alloy steel - Part 1: Bolts, screws and studs. As for an 8.8 part having a shear/tensile ratio of 210/800, that is not supported by my experience or references. A value of 0.6 is listed in VDI 2230, Systematic Calculation of High Duty Bolted Joints and SAE Technical Paper 770420, Analysis and Design of Threaded Assemblies.

 

[Kenneth]

http://www.hobson.com.au/class_8.htm

Do not confuse the SAE "Grade 8" hardware (150 ksi UTS; 130 ksi Yield) with Metric "Grade 8.8" hardware (116 ksi UTS; 93 ksi Yield).

 

[cups]

Whilst I agree that the ultimate shear will be o.62 of UTS it must be remembered that the shear capacity will be less than that. The bolt will be permenantly deform befor it breaks completely. The shear capacity can be taken as 60% of the Yield stress x 90% of the cross sectional area.

 

[CoryPad]

cups,

Interesting comments. Can you provide a derivation or reference for your numbers?

 

[cups]

It's covered by BS 5950: Pt1 2000