# 18538 Shear Pin(s)



## blane (Aug 12, 2004)

Hi all,

I recently acquired an 18538 blower and am trying to understand how the shear(?) pin(s) are suppose to work. In the exploded diagrams shown on this site item #41 is called a Drive Pin and item #42 is called a Shear Pin. What are these pins? Roll pins? Why is there 2? Why are they called different names when they go through the same pieces of steel?

Thanks in advance,
Blane


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## guest2 (Dec 27, 2003)

Hi Blane
Welcome to TF! I don't see any difference in the two aside from the diameter. Seems from the diagram that if the shear pin snapped the drive pin would still be holding it.

My experience on the older flat back sno-thrower is the chain breaks if you hit something like a sewer cap.


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## blane (Aug 12, 2004)

Hi Sixchows,

Thanks for the welcome. I have been lurking here for a while. 

In regard to your response I don't see how one pin can break and the other can't. They both go through the same pieces of metal. They have different names but they both seem to be the same thing (roll pins). When I received my blower the smaller hole (3/16") had a roll pin in it. In a bag of hardware that came with the blower were a couple of larger roll pins that would seem to fit into the larger hole (1/4"), but I'm not sure... Why would they have different names if they seem to be the same thing?

What is everybody else doing? Leaving the larger hole empty? Does the small roll pin have enough strength to keep from shearing everytime moderate resistance is met?

Thanks in advance,
Blane


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## guest2 (Dec 27, 2003)

Blane

They might have different strengths. I wouldn't worry too much about them breaking. Just be sure each hole has the proper pin. My older style blower doesn't have any shear pins and aside from my brother hitting a sewer cap about 25 years ago and breaking the chain, nothing else was ever a problem. Didn't even bend anything, just the chain snapped.


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## henrylimmer (Nov 12, 2004)

I have a 18538 snow caster that I believe to be pretty much factory original save the new chain I just put on. Mine has the smaller of the two pins, I think it's called the drive pin, but has never had the larger pin as the hole is still completely painted without any scratches at all. I think the larger hole may be there to use a normal bolt as a shear pin if the factory roll pin brakes. A grade 2 bolt would have to be larger to have the same shear strength as a hardened steel roll pin. Just my initial thought.



> _Originally posted by blane _
> *Hi all,
> 
> I recently acquired an 18538 blower and am trying to understand how the shear(?) pin(s) are suppose to work. In the exploded diagrams shown on this site item #41 is called a Drive Pin and item #42 is called a Shear Pin. What are these pins? Roll pins? Why is there 2? Why are they called different names when they go through the same pieces of steel?
> ...


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## blane (Aug 12, 2004)

Thanks for the response.

The larger hole you are referring to as maybe a place to put a bolt if the roll pin brakes sounds plausable. However, my blower (new), same as yours, came with an extra roll pin the exact size of the larger hole. As if the small one were to brake or keep braking you could put in the larger one or one in the larger hole and one in the smaller hole???

Thanks,
Blane


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