14 Replies Latest reply on Oct 28, 2014 11:40 AM by Robert D.

# Shear Pin Calculation

I need help determining a shear pin diameter. I have a material with ultimate shear of 107,025 PSI and a shear force of 40,000 PSI in single shear. I am just having a brainfart today. Thanks for any help. Formula I use is tau=f/a

• ###### Re: Shear Pin Calculation

Robert,

Your brain fart is coming from confusing stress and force.

F = shear [lbs]

A = Area = pi*d^2/4 [in^2]

Tau = F/A [psi]

S = shear strength = .58*Yield strength (not ultimate strength) [psi]

Solve for D (check me):

Tau < S

F/A < S

F/S < A

F/S < pi*d^2/4

sqrt(4F/(pi*S)) < d

If you have computed the shear stress = 40 ksi, then you are finished. Your safety factor is 2.7. But I suspect you need to know the shear force in lbs.

Edited to add S to final line

• ###### Re: Shear Pin Calculation

Looks good but I am calculating a shear pin that will shear when 40,000 lbf are subjected to it. That is why I was using the ultimate shear stress. I am trying to determine the DIameter that the shear pin needs to be. Thank you for your help.

• ###### Re: Shear Pin Calculation

The materials ultimate shear is 107025 psi

• ###### Re: Shear Pin Calculation

Then you are ready to go: sqrt(4F/(S_us*pi)) < d.

You had written 40,000 psi, rather than lbs.  It was a little confusing.

• ###### Re: Shear Pin Calculation

I got an answer of .905792in^2 as the diameter?

• ###### Re: Shear Pin Calculation

I think I can leave out the safety factor since I want it to shear?

• ###### Re: Shear Pin Calculation

I get .689 in = sqrt[4*40000/(pi*107025)].

• ###### Re: Shear Pin Calculation

Now if I have 3 pins in single shear on the same plane and subjected to the same force how does that work? Does the math get divided by 3?

• ###### Re: Shear Pin Calculation

I'd have to see a sketch.

• ###### Re: Shear Pin Calculation

Here is an assembly showing what I am trying to do.

• ###### Re: Shear Pin Calculation

If you fix one ring and force the other ring axially, or vice versa, the simple stress on the testpin components is F/3A, like you said. There are also stress concentrations here, though, if this is a fatigue situation.