8.8 tensile strength

[engineerfin]

I have some 8.8 10mm metric bolts that will experience load in tension. Rated at 830mpa but I am thinking I should be more concerned with thread pullout then tensile. I Could not purchase 10.9 bolts so was wondering if these would work and what the calculation would be for the thread pullout.

 

[engineerfin]

25,000lb? With perfect matching strength threads, I sure would like to see that single m10 lift a mack semi tractor.

 

[SwinnyGG]

25,000lb? With perfect matching strength threads, I sure would like to see that single m10 lift a mack semi tractor.

I don't know what to tell you, the math doesn't lie.

This is why the rule of thumb for most fasteners is a minimum of 1.5D of engagement; once you get beyond that, in most cases the fastener shank is going to fail in tension before the threads strip, which is the failure mode you almost always want.

 

[drawoh]

SwinnyGG,

For an M10[×]1.5 grade[ ]8.8 bolt, I get a stress area of 58mm[sup]2[/sup], or 58[×]10[sup]-6[/sup]m[sup]2[/sup]. A grade[ ]8.8 bolt has a yield stress of around [σ][sub]sy[/sub]=600×10[sup]6[/sup]N/m[sup]2[/sup].

Screw tensile yield: 26kN, or 5900lb.

I used equations from Bickford to work out tensile stress area. You can get these from the Machinery's Handbook. Metric screw grades are explained by the Engineering Toolbox.

--
JHG

 

[SwinnyGG]

Screw tensile yield: 26kN, or 5900lb.

Right.. that's tension. Thread pullout is way higher with 2.54 D of engagement..