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Shear Pin Guide
Quick answer: Shear pins connect a two-stage snow blower's auger to its shaft and are designed to break if the auger hits something hard, protecting the gearbox. Replace a broken pin only with the type your maker specifies, with the engine off, key removed and parts stopped. Never substitute ordinary bolts, which can transfer damage to the gearbox.
What a shear pin does
In two-stage machines the auger is fixed to the drive shaft with special bolts. When a rock, frozen newspaper or chunk of ice jams the auger, the pin snaps, letting the auger spin freely on the shaft instead of forcing the gearbox to absorb the shock. A broken pin is a cheap repair compared with gearbox damage.
Signs a pin has broken
The engine runs and the impeller throws a little snow, but one side of the auger does not turn. You may have heard a bang. Turn the machine off and inspect only after all parts stop.
Replacing safely
- Stop the engine, remove the key, and for battery models remove packs.
- Wait for all moving parts to stop.
- Use the clearing tool to remove any jam; never hands.
- Remove the broken pin pieces with pliers or a punch.
- Align the holes in the auger and shaft.
- Insert the new pin and fit the nut or clip as specified.
- Check the auger turns smoothly by hand only once the machine is fully disabled, then reassemble.
Which pins to use
Pins are rated to break at a specific load. A stronger bolt may not break, transferring force to the gearbox. Buy pins listed for your model number, and keep spares. Some machines use different pins for different augers.
| Do | Do not |
|---|---|
| Keep spares of the specified pin | Use hardware-store bolts |
| Lubricate the auger shaft per the manual | Ignore repeated breaks |
| Inspect after impacts | Clear jams by hand |
Repeated breaks
If pins break often, the auger may be seizing on the shaft from rust, or you may be hitting hidden objects. Lubricate per the manual, clear the area before storms and raise skid shoes on gravel.
Single-stage machines
Single-stage machines usually do not use shear pins; they rely on a belt that can slip. Inspect the belt and paddles instead.
Anatomy of the auger assembly
The auger shaft runs across the housing, driven by a gearbox in the centre. Each auger half slides over the shaft and is held by one or more pins passing through matching holes. The pins are made of a material calibrated to fail under a specific load. Some machines add a nylon bushing or spacer; note how pieces fit before disassembly.
What causes breaks
Frozen newspapers, rocks, door mats, dog toys, ice chunks from the plow ridge and edging stones are frequent culprits. Ice that refreezes the auger to the housing overnight can also snap pins at start-up. Clearing the area before a storm and running the machine briefly after use to clear snow help prevent breaks.
Tools to keep on hand
A small bag with spare pins and their nuts or clips, pliers, a punch and a hammer, and a socket or wrench to fit the pin nut cover almost every replacement. Store the bag on the machine or nearby so you are not hunting for parts in a storm.
Removing a stuck pin
A broken pin can leave pieces jammed in the holes. Tap them out with a punch. If the auger has rotated relative to the shaft, turn it gently to line up the holes, only after confirming the machine is disabled.
Lubrication
Many manuals call for lubricating the auger shaft through grease fittings or by removing the pins and oiling the shaft. This stops the auger seizing to the shaft, which can make pins break more often and prevent the protection from working.
Checking after replacement
Once fitted, restart and engage the auger briefly away from people. Both sides should turn. Listen for scraping or unusual noises; stop and check if you hear any.
Why ordinary bolts are dangerous
An ordinary bolt is designed not to break. When the auger jams, the force goes to the gearbox, which can crack housings or strip gears. That repair costs far more than a pack of pins.
Buying the right pins
Use the model number to find the part number. Packs labelled for many models may not match yours.
Other protective features
Some machines use shear bolts on the impeller or slip clutches. Know your machine's design.
Carrying spares
Keep a small bag of the correct shear pins and cotter pins taped to the machine or in a pocket during storms. Replacing a pin takes a few minutes with a hammer and punch, but only if the right parts are at hand.
Why only use rated pins
Using bolts in place of shear pins removes the protection and can damage the gearbox or auger shaft.
Replacing a shear pin step by step
Stop the engine, remove the key and disconnect the spark plug wire. Wait for all motion to stop. Line up the holes in the auger and shaft, tap out the broken pin pieces with a punch, insert the new pin and secure it with the cotter pin or nut supplied. Rotate the auger by hand to confirm it turns freely before restarting. If pins keep breaking, check for a bent auger or seized bearing.
Finding the right part
Use the model and serial number to order pins.
Spare count
Carry at least two spares.
Worked example
Illustrative examples (2026-10-29), not quotes or guarantees.
Two-stage 24 in hits a frozen newspaper; the left auger stops. Engine off, key out, wait. Clearing tool removes debris. Two pins snapped; replace with the two specified pins from the spares bag. Total about 10 minutes.
FAQ
Can I use a grade 5 bolt?
No; use only specified shear pins.
How many spares?
At least two sets.
Do battery two-stage machines have pins?
Many do; check the manual.
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