# What is shear stress on the Key

1. Oct 7, 2016

### Sean Trainor

Hi guys,

I'm trying to work out the following:

Assume uniform shear stress distribution across "Key" width.

What is the shear stress (psi) on the "Key" at the interface with the "Shaft"?

Torque (in-lb) = 4959
Shaft diameter (in) = 2
Key width/height (in) = 0.3
Key length (in) = 2

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2. Oct 7, 2016

### Nidum

How could key as shown in your drawing transmit any drive forces between shaft and gear ?

3. Oct 7, 2016

### Sean Trainor

What do you mean?

The question above is one which was put to me while doing an online test regarding FEA software. Most questions were based on the software which was fine, but then a few questions required hand calculations. And i'm rather rusty when it comes to that since I haven't done any since uni :-)

4. Oct 7, 2016

### Nidum

You describe a plain rectangular key . For this to work properly half of the depth of the key has to be in the shaft and half in the gear .

5. Oct 7, 2016

6. Oct 7, 2016

### Rajesh Shirsagar

At the point when a key is utilized as a part of transmitting torque from a pole to a rotor or center, the accompanying two sorts of strengths follow up on the key : ... (b) Forces (F) because of the torque transmitted by the pole. These strengths produce shearing and compressive (or pounding) stresses in the key.

7. Oct 8, 2016

### JBA

Assuming that a key is installed as shown in Nidum's figure the key's shear line is the radius of the shaft and the key's shearing area = the key width x key length.
The amount of applied shearing force = the applied torque / shaft radius
As a result, the key's shearing stress = (torque / shaft radius) / (key width x key length)