Force consideration on a gripped object

In summary, the grip between the workpiece and chuck jaws is affected by the forces acting on the chuck during turning. Centripetal force is also an important factor.
  • #1
umair20
14
0
If an object say a cylindrical body is gripped in a frame and that frame is being rotated by some mechanism, what forces should be considered on the gripped object in order to know the necessary force required for a proper grip?
 
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  • #2
I'm not sure what the situation would look like exactly, but I think that at least you need to consider static friction. If you would include a sketch of the model, one could be more precise.
 
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  • #3
In order for the grip not to slip you would want the max friction force between the frame and cylinder to be greater than the torque transmitted between the same.

The max friction force is usually dependant on the force clamping the two surfaces together (eg the frame to the cylinder) and the coefficient of friction (which depends on the materials). However that's a simple model which assumes the coefficient of friction is a constant and it isn't always like that.
 
  • #4
CWatters said:
In order for the grip not to slip you would want the max friction force between the frame and cylinder to be greater than the torque transmitted between the same.

The max friction force is usually dependant on the force clamping the two surfaces together (eg the frame to the cylinder) and the coefficient of friction (which depends on the materials). However that's a simple model which assumes the coefficient of friction is a constant and it isn't always like that.
What about the centripetal force? Would we have to consider it?
 
  • #5
Draw the free body diagram for the object . Identify what forces have to act on the body to make it follow a circular path .
 
  • #6
umair20 said:
What about the centripetal force? Would we have to consider it?

You will have to tell us more about the system. I've been imagining something like a jar opener used to unscrew the lids of jam jars. They don't tend to rotate the lid fast enough for centripetal force to be an issue!
 
  • #7
CWatters said:
You will have to tell us more about the system. I've been imagining something like a jar opener used to unscrew the lids of jam jars. They don't tend to rotate the lid fast enough for centripetal force to be an issue!
Well, the system is a lathe machine in which a chuck is holding a shaft and it is being turned at high rpm.
 
  • #8
Workpiece held in a lathe chuck is positively constrained in the radial direction by the chuck jaws .

Axial movement of the workpiece is prevented by friction acting between workpiece and chuck jaws .
 
  • #9
Nidum said:
Workpiece held in a lathe chuck is positively constrained in the radial direction by the chuck jaws .

Axial movement of the workpiece is prevented by friction acting between workpiece and chuck jaws .
Do tangential forces acting on the chuck during turning have any impact on the grip between workpiece and chuck jaws? Also, will we consider the effect of centripetal force on workpiece?
 
  • #10
The workpiece is driven round against the cutting load by the tangential friction forces acting between chuck jaws and workpiece . For any given chuck and workpiece combination the maximum available friction force is set by the chuck jaw radial closing force .

It can happen that at very high turning speeds the radial jaw closing force becomes reduced and hence the gripping force becomes reduced . This is not a common problem though with modern equipment and normal working practices .

Tends to be more of a problem with hydraulic and pneumatic operated chucks than with simple mechanically operated chucks .

Main problem with large chucks running at very high speeds is that they can burst . Again not a common problem though it has happened . For this reason all new chucks have a maximum safe operating speed specified by manufacturers .

Discussion so far has been about balanced chucks and round bar workpieces . The situation with unbalanced set ups and odd shaped workpieces is much more complex .
 
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Related to Force consideration on a gripped object

1. What is force consideration on a gripped object?

Force consideration on a gripped object refers to the analysis and understanding of the various forces exerted on an object when it is being gripped or held. This includes both the external forces acting on the object, such as gravity and applied forces, as well as internal forces within the object itself.

2. Why is force consideration important when gripping an object?

Force consideration is important when gripping an object because it allows for a better understanding of the forces at play, which can help prevent damage or injury. By considering the forces on an object, one can determine the safest and most effective way to grip and manipulate it.

3. How does force consideration affect the grip strength needed?

Force consideration can affect the grip strength needed in a few ways. For example, the weight and shape of the object, as well as the forces acting on it, can determine how much force is required to grip and hold it securely. Additionally, the grip strength needed may change depending on the direction and magnitude of the applied forces.

4. What factors should be considered when gripping an object?

When gripping an object, factors such as weight, shape, surface texture, and the forces acting on the object should be considered. Other factors like the size and strength of the person gripping the object, as well as the intended purpose of the grip, should also be taken into account.

5. How can force consideration be applied to improve grip strength?

By considering the external and internal forces on an object, one can determine the most effective way to grip and manipulate it. This can help improve grip strength by allowing for a more secure and stable grip. Additionally, knowing which muscles to engage and how to distribute force can also improve grip strength.

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