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Shear Pin for 816?

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ACHiPo

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#1
After crunching my quick change gear box, I'd like to add a little protection (not that I'll likely do it again!) I'm thinking of replacing the pin holding the spindle to the gear box with a shear pin. I could use aluminum or brass, and I'm wondering if I should score it so it will shear more easily, or if that will just cause premature failure when in normal operation?
 

mikey

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#2
I would use aluminum, which has a pretty low shear strength. My Emco lathe uses aluminum pins between the gear train and leadscrew.
 

ACHiPo

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#3
Mike,
Does the pin have a notch or is it just a cylinder?
 

mikey

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#4
Not scored, just a straight pin.
 

Superburban

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#5
Trying to design a shear pin for a new application, can drive you crazy. When I made one for my PTO winch, I started on the safe side, and made them with smaller diameters at the shear points. After several tries, I realized that I can measure the shear torque by locking one side, and using a torque wrench on the other side, to see what it takes to shear them.

Then of course the other issue, is what torque do you want to strive for?
 

Ulma Doctor

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#6
aluminum would be fine.
you could centerdrill the pin with a wire drill during construction, if you are looking for a pin that's a bit easier to break in a bad situation
 

ACHiPo

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#7
Trying to design a shear pin for a new application, can drive you crazy. When I made one for my PTO winch, I started on the safe side, and made them with smaller diameters at the shear points. After several tries, I realized that I can measure the shear torque by locking one side, and using a torque wrench on the other side, to see what it takes to shear them.

Then of course the other issue, is what torque do you want to strive for?
About 1 ft-lb less than my gear train will break at;)
 
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