What Are Shear Pins on a Snow Blower and Why Do They Break?

Last updated: October 2026

A shear pin is a small bolt that connects a snow blower's auger to its drive shaft. It is made to be the weakest link. If the auger hits a rock, a frozen newspaper or a chunk of ice, the pin snaps and the auger stops turning, which protects the gearbox and motor. Replacing a pin takes minutes. Replacing a gearbox does not.

What does a shear pin do?

In a two-stage snow blower, a shaft turns the auger, the metal spiral at the front that gathers snow. The auger is not welded to that shaft. It is held by one or more pins that pass through both.

In normal use the pin carries the full turning force. When the auger jams against something that will not move, the force spikes. The pin is sized to break at a load well below what would damage the gears. It shears cleanly, the shaft keeps spinning inside the auger, and nothing expensive is hurt.

Think of it as a fuse. A fuse blows to save the wiring. A shear pin breaks to save the drivetrain.

Why do shear pins break?

Almost always because the auger met something solid:

• Stones and gravel, especially on unpaved or broken driveways.
• Ice chunks in the ridge left by a street plow.
• Frozen newspapers, doormats and packages under fresh snow.
• Toys, dog chains, cords and hoses.
• Branches brought down by the storm.
• Frozen-solid snow if the machine sat with wet snow packed in the housing.

Less often, a pin fails from age: rust or many seasons of load.

How do you know a shear pin has broken?

• The machine runs and the impeller may still spin, but one side of the auger has stopped turning or the whole auger sits still.
• Snow stops feeding from one side, or the machine pushes snow ahead of it.
• You may have heard a sharp snap or clunk just before.

Stop the machine as soon as you notice. Running with a broken pin clears nothing.

How do you replace one?

Follow the manual for your machine. The general steps are the same on most two-stage blowers:

1. Power off completely and make sure nothing can start. On a robot, shut it down as the maker instructs before going near the auger.
2. Wait for all parts to stop.
3. Clear the jam with a tool, never a hand.
4. Line up the holes in the auger and the shaft.
5. Remove the broken pieces. A punch helps.
6. Insert the new pin and secure it with its cotter pin or nut.
7. Turn the auger by hand to confirm it is engaged.

Never put your hand in the auger housing or chute of a machine that could move.

Can you use a regular bolt instead?

No. This is the most important rule. A shear pin is a specific size, material and strength. A hardware-store bolt is usually stronger, which means it will not break when it should, and the next jam goes straight to the gearbox. Use only the pins the maker specifies for your machine.

What shear pins does a Yarbo use?

Yarbo sells a Shear Pins and Cotter Pins Set with 8 shear pins and 8 cotter pins. Per Yarbo, they are designed specifically for the Yarbo Snow Blower Module and are a critical safety component for snow blower operation.

Keep a set where you can find it in January.

Why do shear pins matter more on a robot?

A person behind a snow blower sees the newspaper and stops. A robot follows its map. Yarbo's snow blower detects obstacles with binocular cameras and a bumper, but an object buried under several inches of snow is invisible to any camera.

Two habits make up for that:

• Walk the driveway before a storm and pick up anything loose.
• Keep spare pins on hand, because a robot with a broken pin stops clearing until someone replaces it.

How many spares should you keep?

Enough that a bad storm does not end your snow clearing. A set of 8 covers most winters. If your driveway is gravel, borders a street that gets plowed hard, or collects a lot of debris, you may use more.

How do you avoid breaking them?

1. Clear the area first. Mats, cords, toys, branches.
2. Grade and pack gravel in fall. See snow blowers on gravel.
3. Mark edges with stakes so the machine stays on the driveway.
4. Take the plow ridge slowly and in partial-width bites. See clearing the end of the driveway.
5. Clear snow from the housing after use so it does not freeze into a block. Yarbo's Snow Shovel tool is made for removing buildup.
6. Do not let wet snow sit in the machine overnight in freezing weather.

Do single-stage snow blowers have shear pins?

Generally no. A single-stage machine uses a rubber-edged paddle driven by a belt, and the belt or paddle gives when it hits something. Shear pins belong to two-stage and three-stage machines with metal augers. See single-stage vs two-stage.

What else wears on a snow blower?

Shear pins are the part that fails suddenly. Others wear slowly:

• Scraper bar. The edge along the bottom of the housing. Yarbo's Scraper Bar is wear resistant steel with a serrated edge.
• Tracks. Inspect and grease. See Yarbo Track Grease.
• Skid surfaces and chute. Check for wear and smooth movement.

Our Yarbo winter checklist covers a full pre-season inspection.

Is a broken shear pin covered by warranty?

A shear pin breaking is the part working as designed, and pins are consumables. Yarbo's 2-year limited warranty covers the Core and modules per Yarbo's warranty policy. For what is and is not covered in a specific case, ask us and we will help you check with Yarbo.

What is the takeaway?

Shear pins break so that nothing else does. Keep the right ones on the shelf, never substitute a bolt, clear the driveway of loose objects before storms, and a broken pin is a five-minute pause instead of the end of your winter.

Find pins and other winter parts in Yarbo parts and accessories.

Still not sure which fits your property?

Tell us about your snow blower, driveway surface and what it tends to hit and a Yard Automation Pro will reply by email with a recommendation, or tell you honestly if none of our machines fits. Book a free consultation, or call +1 423-927-3776, 9am to 5pm EST. You can also try the Find Your Robot quiz and cost calculator.