Shear Pins to Protect Your Equipment

 If you have a piece of equipment that gets turned by a shaft connected to a motor, you probably have one or more shear pins in it.

 A shear pin is a safety device designed to shear in the case of a mechanical overload, preventing other, more expensive or less-easily replaced parts from being damaged. As a mechanical sacrificial part, it is analogous to an electric fuse.

 My son inherited a 24 inch snowblower from my father, so it is probably 10 - 12 years old. It has been used pretty hard since we live in farm country and our driveways are long and the parking lots at our houses are large. This snowblower has been used to clear snow at three different properties.

 I used my son's snowblower today to clear a path and noticed that it wasn't throwing snow very well and it also hard a hard time moving forward. I suspected that the drive belt was loose, but when I took it to my garage to work on, I noticed there was no air in the tires and the rims were just spinning inside the tires. That was an easy fix.

 This snowblower has four shear pins for four separate blades in the chute. 

 As you can see, there is nothing in the hole. The hard part about replacing the pin is lining up the hole to the sheared off pin so that you can drive it out with a hammer and drift pin (or pin punch, whatever you call it where you live). This one was easy to line up because the pin was not cleanly sheared off, it was jagged, and easy to see.

 This shows the next section of blades with the proper shear pin in place.

 Here is what was left of the pin once I drove it out of the shaft. It had not been broken long and was not rusted fast. I have a snow blower on my Kubota tractor and I had to drill out a broken shear pin and that was tough to do.

 The sheared pin at the bottom, a whole pin in the middle, and the retaining clip for the pin at the top. This is a commonly used pin for small snow blowers so I won't have any trouble getting replacements. I I have two parts trays full of assorted shear pins but they are for larger pieces of equipment. Lowe's and Tractor Supply both carry this style and size pin.

 Word of warning. I have a temporary pin in place until I can go get the proper ones. It is a shear pin of the right diameter, but it is too long. NEVER insert a bolt as a shear pin. Bolts are generally too hard and will not shear properly and you are likely going to really damage your equipment.

 Now, there are "Shear Bolts" for larger, heavier duty pieces of equipment such as a rotary mower, but they are marked by "grades". Grade 2 and Grade 5 are the two most common Shear Bolt grades.

 You can identify these bolts by the chart below. But, I wouldn't rely on it 100% if you inherited or bought a big can of misc. bolts. Your best bet, to protect yourself and your equipment, is to buy the exact shear bolts and shear pins that you need for your equipment, put extras in a bag or tray, and clearly mark what they are for.