Tuning Pin Size

[larudee@pacbell.net]

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Terry,

All of what you mention affects shearing, but the bottom portion also
affects it by concentrating the shear forces at the point where the
diameter changes.  In other words, the greater the difference, the more
torsion and flex will end at that point and the less those forces will
be distributed thoughout the pin.

Paul

Farrell wrote:

>  "The larger the size difference between the two portions, the greater
> the risk." Why would that be? I should think the point at which a pin
> would shear would depend entirely on the metal composition (let's
> assume this is constant), its diameter, and the tightness of the
> pin/block fit (torque). As you make any pin size fit tighter in the
> block, it will get closer to its shear point. As you make any pin
> smaller in diameter, you will move toward a lower shear point.
> Diameter and torque - I think that is all. Why would the diameter
> contrast between the top and bottom portion affect its shear strength?
> Is there something about the machining process? Or do you mean (by the
> above quote): 'The smaller the diameter of the top portion of the pin,
> the greater the risk of shearing' (because, of course, the smaller
> diameter pin will have a lower shear strength, and will shear at a
> lower pin torque). How would the diameter of the bottom portion of the
> pin affect the shear strength? I am assuming that the rebuilder will
> drill/ream/whatever the hole to a proper diameter for the diameter of
> the pin bottom portion. Terry Farrell

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