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How to Tell if Shear Pin is Broken (this is how)

By: Author John Cunningham. Published: 2022/09/02 at 4:46 pm

Got to love those shear pins; always looking out for your snow blower gearbox and engine. Yep, a broken shear pin is good news indeed, and you are lucky. I’m a small engine mechanic, and very shortly, you’ll realize how lucky you are, and you’ll be back moving snow.

To diagnose a broken Snow blower shear pin, follow these three steps:

  1. Snow blower engine off
  2. Auger lever off
  3. Turn the auger by hand; a free-spinning auger means the shear pins are broken

In this post, you’ll learn how to diagnose a broken Snow blower shear pin, and you’ll learn how to fix it, but also the importance of fitting the correct shear pins for your machine.

Index

What Are Shear Pins & What Do They Do?

A snow blower shear pin is a metal fastener with a serious job. Sure, we all know what a fastener does, but a shear pin (also known as a shear bolt) has another, even more important job.

A shear pin is designed to break when your auger hits a solid object. If your snow blowers auger had regular bolts fitted, chances are you’d be searching the internet for a new gearbox right now, or worse, an engine.

Shear-bolt

The unassuming and inexpensive shear bolt is an insurance policy against your auger meeting something it can’t handle.

A frozen newspaper was typical but becoming rarer; a dog’s toy is now the most likely reason a shear pin breaks.

Symptoms Of Broken Snow Blower Shear Pins

The main symptom associated with a broken Snow blower auger shear pin is – Snow blower only moving snow on one side.

But you’ll likely recognize some of the following symptoms. They all point to broken shear pins.

Diagnosing Broken Shear Pin

Diagnosing broken Snow blower shear pins is a thirty-second job.

The 3-step process is as follows:

One-auger-spinning
  1. Machine engine off
  2. Auger lever off
  3. Turn each auger by hand slowly

A free spinning auger means the shear pins are broken.

Importance Of Fitting Correct Shear Pins

It is worth noting that many an enterprising snow blower operator has replaced the shear pin with a makeshift bolt only to get caught out later. You guessed it, a regular bolt might bend a little but won’t break, which means all the energy goes into the gearbox or the engine, which may bend something spendy like a gearbox or crankshaft.

Also, many snow blowers come with a spare set of shear pins, so if you can remember where the manual is, the spare pins may be there, too; otherwise, I’d recommend postponing the job until you have the pins. Top tip, buy a few extra pins.

How To Fit Snow Blower Shear Pins

Replacing a shear pin is an easy job; with the correct tools and pin to hand, you’ll be back moving snow in about ten minutes tops.

You must fit specific shear pins, though, not just any shear pins; you’ll need the pins calibrated for your snow blower. When fitting the pins, it’s important not to overtighten them; this may prevent them from breaking when designed. Anyhow, it’s all covered in this post “Snow blower auger spins freely”

Grease new shear pin

I’ve covered fitting snowblower shear pins previously, including pictures, and you can check that post out here “Snow blower auger spins freely”

How to Prevent Shear Pin Damage

A broken shear pin here and there happens; it’s called life, right? That said, if you fit more than the occasional shear pin, and unless you are hitting a ton of dog toys, then you likely have one of the following issues.

  • Shoes are worn out
  • Shoes are set too low

Replacing or adjusting the shoes will solve this issue.

Lower the skid shoes

Your shoe height determines how low the scraper bar is to the yard surface; the lower we get, the more likely we’ll pick up stones and rocks capable of breaking our shear pins.

If you find you are replacing more than your fair share, check the height of your scraper bar; the bar should be level; if it isn’t, check your tire pressure. The recommended pressure is written right there on the tire, usually about 20 Psi.

Now check that scraper bar height again; if it’s less than one inch and you have a stone drive, you’ll need to drop those shoes a touch. I’ve covered the whole process previously, and you can check it out here “Can Snow blowers be used on gravel driveways?”

Sum Up

A free spinning auger is a sure sign a shear pin has broken. Fitting the correct pin is important; shear pins, as you know, are designed to break to protect your gearbox and engine. Take care when fitting the shear pins; overtightening prevents them from shearing.

You may also find the following posts helpful:

Snow blower auger spins freely

Snow-blower

Snowblower Troubleshooting Page