Trying to understand shear bolts. I have only ever needed/used shear bolts for a snowblower, which you buy as specifically designed bolts, usually with a groove cut in them at the point where they are designed to shear. The PTO driven drive shaft for my wood chipper has a shear bolt on the wood chipper end of the drive shaft. The chipper came with a couple spares but they do not have a groove machined into them like the snowblower shear bolts. The chipper specifies "M8x50mm Hex Bolt Class 8.8 (Grade 5)". I can find these bolts at HD or TSC but they are not called "shear bolts" nor do they have a groove machined into them at the point they are supposed to shear, they are just regular bolts that can be used for any application. Are these appropriate to use as "shear bolts" or do I need to look for a specific bolt called a "shear bolt". IOW can a regular bolt be used as a "shear bolt" as long as it meets the specs given by the implement manufacture?
Typically shear bolts are sized to use grade 5 alloy. Nothing special is needed…just don’t run grade 8’s. If you try running grade 2, you will just shear them off.
In addition to grooves, shear bolts have "metal" that'll break(where the groove would be) with less force than the rest of the bolt.
Any PTO powered equipment I have owned & operated doesn’t utilize special shear bolts…just need to be correct diameter & grade 5.
Regular grade 5 is quite fine. Only bolts with grooves will be truly called shear bolts. Snowblower bolts are grooved primarily because the small wall thickness of the auger tube will walk over a standard sheared bolt and become a royal pia to get it all apart. A groove gives you a clean burr free break and the pieces come out easy.
Start with Grade 5 and see where that gets you, I have had several experiences with shear bolts. My 6' 3pt blower on my Case had nothing when I bought it. The local tractor house suggested I start at grade 2 and work up. Grade 2 mangled and was a mess to clean out, grade 5 seems to be fine. We had a JD 24T baler that we worked up to Grade 8 before it would even engage w/out shearing. luckily we got the actual bolts from the JD dealer a week or two later. I am guessing they are about grade 10-11.
I went through this with my 3 point PTO tiller. Said same thing as your specs but before I decided to actually download and read the manual, I tried using grade 2 and was a exercise in frustration with them breaking easily. Went to grade 5 TSC bolts and all is well. They do shear at the proper time when I manage to find that hidden rock. Sent from my iPhone using Tapatalk
When I was a kid, we sheared a pin on the baler. Dad grabbed another bolt and it sheared right away. He got a box of them and we spent the rest of the day just trying to finish the one row. They were all grade 2!
