# shear pin question



## ron3033 (Oct 22, 2015)

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. :icon_whistling: 
Thanks ron3033


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## BullFrog (Oct 14, 2015)

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.


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## Kiss4aFrog (Nov 3, 2013)

If you posted the model and serial number we could check if the pins are correct.


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## wdb (Dec 15, 2013)

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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## BullFrog (Oct 14, 2015)

wdb said:


> 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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## ron3033 (Oct 22, 2015)

Kiss4aFrog said:


> 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


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## 43128 (Feb 14, 2014)

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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## ron3033 (Oct 22, 2015)

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?


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## ron3033 (Oct 22, 2015)

43128 said:


> 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)*


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## ELaw (Feb 4, 2015)

ron3033 said:


> *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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## ron3033 (Oct 22, 2015)

So what I have is the right pins, just older.


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## ELaw (Feb 4, 2015)

It sure seems that way!

...Which of course leaves the original question of why your gearboxes keep failing. Do you know what parts were replaced each time? It seems like the gearbox itself is somehow the problem, although I can't really think of how.

As a stopgap measure you could cut the grooves in the shear pins a little deeper with a hacksaw to weaken them, but that's hard to do accurately. Another idea if you had an acetylene torch would be to heat the shear pins in the area of the grooves to a bright red color, then let them cool slowly. That might soften the metal a bit... but again it's kind of a kluge.


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## ron3033 (Oct 22, 2015)

ELaw said:


> It sure seems that way!
> 
> ...Which of course leaves the original question of why your gearboxes keep failing. Do you know what parts were replaced each time? It seems like the gearbox itself is somehow the problem, although I can't really think of how.
> 
> As a stopgap measure you could cut the grooves in the shear pins a little deeper with a hacksaw to weaken them, but that's hard to do accurately. Another idea if you had an acetylene torch would be to heat the shear pins in the area of the grooves to a bright red color, then let them cool slowly. That might soften the metal a bit... but again it's kind of a kluge.


It had, I have bill for parts:
2 56061 seals
1 10108 gasket
1 56062 seal
1 524015 worm gear & shaft
1 54045 bearing cone

http://apache.ariens.com/manuals/PM 24000.pdf

I thought maybe dremel tool with a small wheel to deepen the grooves. It is running, drips one or two drops of oil from gear case in the summer, but not worth total disassembly. I just check oil and in winter I do not believe it leaks, too cold and seals maybe get used.


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## ELaw (Feb 4, 2015)

Well that's a puzzler! 524015 includes both gears, so it's not a matter of one having some damage and not getting replaced.

The only other thing I can think if, and this is a long shot, is maybe there's a tolerance issue in the gearbox housing that's causing the gears not to mesh quite right, and thus be more prone to failing.

I will say that particular gearbox doesn't seem to be one of Ariens' best... I've seen quite a few damaged ones, and had one fail myself. Although in that case it was a machine I bought used, didn't check properly, and thus didn't discover the previous owner had replaced the shear pins with regular bolts. :wacko:


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## ron3033 (Oct 22, 2015)

It runs now and has for a few years, but I do not want to repeat that performance. Other than that I had to get a new throttle cable this year. Would you believe it has 2 different cables?(I assume it has something to do with carb used) And years ago, the dealer who is now out of business ordered me the wrong one! When I went to install it in the spring, it did not fit and he was out of business. So I was stuck with it.


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## Kiss4aFrog (Nov 3, 2013)

The nuts might have a slight "dent" in the flats. They have a crush fit but aren't the best to reuse. The ones I bought recently for a Murray where that way. 










My Murray pins.


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## ron3033 (Oct 22, 2015)

Hi 4 of the nuts had flat spots like your upper photo, & 2 had 2 dots. 180 degrees opposite. All ariens 510015?
How does the murray pin work with that spacer in the middle? Are you using them in an ariens machine?

thanks


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## Kiss4aFrog (Nov 3, 2013)

If the two "dots" were on the flat spots of the nut it's a lock nut. You should be able to notice that as you start the nut it gets tight and doesn't spin on like a regular one would.

The auger has a larger hole on one side that the round spacer fits into.
Can't honestly say I know if it matters is the head or nut end goes over the spacer or if it matters. I bought a bag of them for my Murray as I figured I'd either use them or end up getting a couple more to rebuild and need spares.

I only use whatever the machine is supposed to have. I value my auger boxes to much to mix and match or substitute regular bolts.

However someone mentioned using nails and if I was in a pinch that's an excellent idea. First however I always try to have spare shear pins and belts handy in case they break before I'm able to get the driveway clear.


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## ron3033 (Oct 22, 2015)

Thank you
Good advice


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