shear pin questions?
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Category: Allis Chalmers
Forum Name: Construction and other equipment
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=134698
Printed Date: 04 Nov 2025 at 3:48am
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Topic: shear pin questions?
Posted By: wjkrostek
Subject: shear pin questions?
Date 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. |
Replies:
Posted By: TramwayGuy
Date Posted: 05 Feb 2017 at 2:18pm
| 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). |
Posted By: wjkrostek
Date 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. |
Posted By: Coke-in-MN
Date Posted: 05 Feb 2017 at 3:44pm
------------- Life lesson: If you’re being chased by a lion, you’re on a horse, to the left of you is a giraffe and on the right is a unicorn, what do you do? You stop drinking and get off the carousel. |
Posted By: Coke-in-MN
Date Posted: 05 Feb 2017 at 3:47pm
------------- Life lesson: If you’re being chased by a lion, you’re on a horse, to the left of you is a giraffe and on the right is a unicorn, what do you do? You stop drinking and get off the carousel. |
Posted By: wjkrostek
Date Posted: 05 Feb 2017 at 4:21pm
| 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. |
Posted By: DiyDave
Date 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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Posted By: wjkrostek
Date Posted: 05 Feb 2017 at 8:26pm
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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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Posted By: wjkrostek
Date 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. |
Posted By: Calvin Schmidt
Date 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. ------------- Nothing is impossible if it is properly financed |