# Friction or bearing joint?

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1. Nov 1, 2014

### 9988776655

I have a tapped hole. A threaded rod goes through the hole. A single nut secures the threaded rod in position. Only one plate is threaded. Note the clearance hole in the top plate. A picture is attached.

A friction joint in a bolt occurs when the clamping force creates a normal force. This normal force is designed to be greater than the friction force between the plates. In this way a bolt does not experience any shear load.

I want to know whether or not a threaded tapped joint can be a friction joint. Specifically, if the clamping force is large enough to prevent slip, then will any part of the threaded rod experience shear?

Thanks.

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2. Nov 2, 2014

### jack action

The normal force only depends on the tightness of the bolted joint and the maximum tightness of the bolted joint depends on the yield strength of the bolt. All of this applies whether it is a bolt, a screw or a stud.

3. Nov 3, 2014

### 9988776655

What if there are two threaded fasteners and they are not near each other, each contributing F = uN and each fastener is subjected to a shear force of P/2.
Then does uN > P/2 or does 2uN > P/2 to prevent slipping?

4. Nov 3, 2014

### billy_joule

As usual, drawing a free body diagram is the best first step

5. Nov 3, 2014

### jack action

With the way you chose your words, uN > P/2.

6. Nov 3, 2014

### 9988776655

What do we do when there is an unequal shear force? eg the shear force on fastener 1 is P and the shear force on fastener 2 is J. Lets assume P > J. Lets assume two fasteners. Then does (uN1 + uN2) > (P/2 + J/2) to prevent slipping? or is it just uN1 > P/2 as before

7. Nov 4, 2014

### jack action

uN1 + uN2 > P + J

Ideally (assuming the parts can deform such that some «local» slipping can occur):

uN1 > P
uN2 > J