# Thread: Calculating shear in a pin with known torque value

1. ## Calculating shear in a pin with known torque value

Hello,

I'm working on a design, where a pin is attached to a drum and is used to engage and disengage the drum that is attached to a keyed shaft. I know the torque value on the drum clutch but how do get lb-force unit to calculate allowable shear stress in the pin? I've attached a picture showing how the pin engages into the drum clutch. The drum clutch is keyed to a shaft that is chain driven by a hydraulic motor/gearbox.

Thanks,
Alex

2. See image on bottom for clarity.

Torque = Force x distance
or
T = F x L

and

F x L = Fp x Lp

Thus (algebra)

( F x L ) / LP = Fp

Fp = force on pin
LP= Length from rotation

Determine whether you have single or double shear, then use one of the following links to calculate the shear in the pin.

Single Shear Pin/Bolt Calculator

Double Shear Pin/bolt calculator

pin-force.png

3. Thanks Kelly!

So, with the pin being held by the bushing and the actual torque being applied to the portion of the pin below the bushing (see pic attached) I'm assuming "Lp" would be from the bushing engagement to the center of the material where the pin is engaged in the clutch (clutch being the torque on the pin)? The actual pin length is much longer than where its being held and where the force is applied (2nd pic attached.)pin engage.jpgpin_bushing_clutch.jpg

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