shear pin question - Snowblower Forum : Snow Blower Forums
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post #1 of 19 Old 11-16-2015, 09:25 AM Thread Starter
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shear pin question

I have a 1978 Ariens ST724. I have taken the front gears out of the auger two times. The first time a small stone got between the auger tine and the bucket (tear drop style). The second time I caught a mat at the door step. Neither time did the shear pins snap, thus the gears and shaft stripped out.
The auger is greased and not seized to the shaft, and I have the correct pins.
Why do they not snap, when need be? Is there a chance the shear pins are tightened too much so as the 2 grooves in the pins do not line up to the outer auger shaft?

part #510015, these are likely bought in late 70's early 80's $4.25 for 5.

I attached photos, I hope. Suggestions to what is wrong, just trying to prevent this occurring again.
Thanks ron3033
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post #2 of 19 Old 11-16-2015, 10:30 AM
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You might want to check the part no. of the pins to make sure they are the correct ones for your machine. As for tightening, the shear pins have self locking nuts so you don't need tighten them much, just a bit snug.

Last edited by BullFrog; 11-16-2015 at 10:33 AM.
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post #3 of 19 Old 11-16-2015, 11:01 AM
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If you posted the model and serial number we could check if the pins are correct.

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post #4 of 19 Old 11-16-2015, 12:51 PM
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If the grooves are important to function then yes, they had better be in the right place. It really doesn't make any sense that they did not snap under conditions serious enough to strip gears, unless those grooves are a critical component to their function and the grooves are in the wrong place. I'd be tempted to try another source for shear pins or just go see what new ones look like. (The pins for my Honda have no grooves.)
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post #5 of 19 Old 11-16-2015, 01:52 PM
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Quote:
Originally Posted by wdb View Post
If the grooves are important to function then yes, they had better be in the right place. It really doesn't make any sense that they did not snap under conditions serious enough to strip gears, unless those grooves are a critical component to their function and the grooves are in the wrong place. I'd be tempted to try another source for shear pins or just go see what new ones look like. (The pins for my Honda have no grooves.)
Yes the grooves are important as that is where they are designed to shear at a certain torque specified by the machine's manufacturer. This is why it's important to use the correct shear pin. If your shear pins are factory installed to your blower then they are likely designed to shear without the need of grooves.
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post #6 of 19 Old 11-17-2015, 08:28 AM Thread Starter
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Quote:
Originally Posted by Kiss4aFrog View Post
If you posted the model and serial number we could check if the pins are correct.
Hello Thank You
model 924032 - 008001 7HP ST724 and I think the auger model is 924028

The pins I have are steel, I tried a magnet. No nylon insert in the nut. These are 30 years old, and #'s on the package of pins seem to be the number on the manual.
Are pins now days aluminium?

Thanks
ron3033

Last edited by ron3033; 11-17-2015 at 08:30 AM. Reason: photo
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post #7 of 19 Old 11-17-2015, 08:53 AM
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how tight were they, you should leave some slop in them. in a pinch, i have used nails believe it or not as shears pins. way better grade 5 or 8 bolts
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post #8 of 19 Old 11-17-2015, 08:57 AM Thread Starter
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These Look like they may be brass. I just found on E replacement parts? Maybe steel was what was used long ago? Or are these steel that is coated?

Last edited by Kiss4aFrog; 11-17-2015 at 11:27 AM.
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post #9 of 19 Old 11-17-2015, 08:59 AM Thread Starter
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Originally Posted by 43128 View Post
how tight were they, you should leave some slop in them. in a pinch, i have used nails believe it or not as shears pins. way better grade 5 or 8 bolts
I remember one guy saying he only used brass brazing rods (I believe that is what it was)

Last edited by Kiss4aFrog; 11-17-2015 at 11:27 AM.
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post #10 of 19 Old 11-17-2015, 09:12 AM
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These Look like they may be brass. I just found on E replacement parts? Maybe steel was what was used long ago? Or are these steel that is coated?
That's not brass, it's zinc-plated steel. The plating is incredibly thin, which causes the coloration. The older ones were plated too, but the plating was thicker so it had the silver color.

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