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wjkrostek 
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Joined: 18 Dec 2010
Location: Wasilla alaska
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 Topic: shear pin questions?
Posted: 05 Feb 2017 at 2:12pm |
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I'm running a 87 inch snowblower and have been shearing a lot of PTO shear bolts but the bolts have been shearing because of drifted snow. What I have been using is no grade bolts as shear pins and they are ok for snow but a little light on the drifts. So what I wanted to find a little stronger bolt like a grade 3 but no one has them up here. So it's either a non grade mark (which no one knows what grade they are 0,1,or2) or a grade 5. I have been using the grade 5 now with no problems. I am being easy on her but I'm concerned about the gear box . What grades are you all using as shear pins. Has anyone ever ever had a gear box broken before a grade 5 bolt sheared to save it? I'm just picking your brains to save me some trouble . I have been blowing snow for 20 years and I think I got into a soft batch of bolts but there is no way to check them for what they are. thanks for your time and ideas.
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TramwayGuy
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Joined: 19 Jan 2010
Location: Northern NY
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Posted: 05 Feb 2017 at 2:18pm |
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I've never seen a grade 3 bolt. Normally an unmarked bolt is Grade 2. 3 marks on the head is Grade 5; 6 marks are Grade 8. (Not to be confused with metric designation of 8.8).
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wjkrostek
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Joined: 18 Dec 2010
Location: Wasilla alaska
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Posted: 05 Feb 2017 at 2:53pm |
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I used to think the same thing until I started looking up all the different bolt specs. There are a dozen or so of unmarked bolts have a large range of specs. But normally an unmarked bolt using sae standard is a grade 1,2or 4. So you just don't know.
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Coke-in-MN
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Joined: 12 Sep 2009
Location: Afton MN
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Posted: 05 Feb 2017 at 3:44pm |
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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."
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Coke-in-MN
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Posted: 05 Feb 2017 at 3:47pm |
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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."
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wjkrostek
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Joined: 18 Dec 2010
Location: Wasilla alaska
Points: 131
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Posted: 05 Feb 2017 at 4:21pm |
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None of these markings id the shear point on these bolts because there isn't one. It is thought to be about 60% of the tensile. My question is what are others using and has anyone trashed there gear box using grade 5 bolts for shear bolts. There are a lot of bolt makers and not all are SAE specs. So no making don't tell you much and it's not important normally.
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DiyDave
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Location: Gambrills, MD
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Posted: 05 Feb 2017 at 6:00pm |
Snowblowers are generally a little more forgiving, than a bush hog, or tiller. As long as you set them up above rocks, I'd go a grade harder, or drill the hole a size bigger. I've got a bush hog, on the kuboter, that has had a grade 8 bolt in it for about 5 years, but most of the areas I mow with it, I know well... 
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wjkrostek
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Location: Wasilla alaska
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Posted: 05 Feb 2017 at 8:26pm |
That the kind of info I was looking for. Your using a grade 8 without breaking but I wandering if your lucky or just good. Have you ever used grade 5? You didn't but grade 8 in because you were breaking grade 5 bolts did you?
In a way I was hoping I would break a grade 5 so I know there was some kind of protection on my gear box. But I'm trying not to push it that far. I know what it takes to break the ones I have now so I sort of stop when I get there. I think the last batch of bolts I bought were weaker than the one I had before. I must of bought them years ago. With no markings there is no way to tell what they are and who made them to what specs. Thanks for your info.
bill
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wjkrostek
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Location: Wasilla alaska
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Posted: 06 Feb 2017 at 10:03am |
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I found my answer. I heard back from the company they said for as far back as anyone can remember they tell you to use 10mm grade 8.8. So at least in this case I can use the grade 5 and feel safe. I have been using 3/8 so when I break these I can try a 10 mm it is a little bigger. Thanks for your input.
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Calvin Schmidt
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Joined: 11 Sep 2009
Location: Ontario Can.
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Posted: 10 Feb 2017 at 2:14pm |
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I always used grade 5 shear bolts. The key is to have a proper diameter fit and keep them tight with a lock washer or lock nut. On the roller mills that I sell and rent, we have to use lock nuts on the PTO shear bolts or they work loose and shear.
Edited by Calvin Schmidt - 10 Feb 2017 at 2:15pm
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