Why do Pellet Stove Motors Use a Pin Hole Shaft?

When inspecting the feed motor for pellet stoves, we often notice a small horizontal through-hole in the middle of the motor’s output shaft. Typically, a milled-edge shaft would suffice for the motor’s function. Why, then, is this hole required in the shaft for pellet stove applications?

Drawing on years of experience designing and manufacturing pellet stove motors, Fengtech explains the rationale from the perspectives of reliability, safety, stability, and ease of subsequent maintenance.

1. Working Principle

The shaft with a hole in the middle is called a “perforated shaft,” primarily used for pin-type connections.
In applications, the auger is typically connected to the motor shaft in the following ways:
Spring pin
Dowel pin
Shear pin
The pin passes through the connecting holes of both the motor shaft and the auger, forming a complete mechanical locking structure.

2. Advantages of Using a Perforated Shaft

Let’s examine why this design is exceptionally well-suited for the operating environment of pellet stoves: Pellet Stove Operating Characteristics:

Operating Condition	Impact on Shaft Connection Reliability
Proximity to combustion chamber (high-temperature environment)	Reduced reliability of friction-based connections
Extended continuous operation	Higher risk of slippage under constant torque
Frequent start-stop cycles	Significant torque shocks and mechanical stress
High levels of wood chips and dust	Threaded fasteners are prone to seizing or failure

In such demanding conditions, standard milled shafts are highly prone to failure. The perforated shaft + pin connection avoids many issues due to these key advantages:

Design Feature	Performance Advantage
No reliance on set screws or threads	Eliminates friction dependence, effectively preventing slippage
Resistance to thermal expansion and contraction	Maintains reliable locking performance in high-temperature environments
Strong vibration resistance	Positive mechanical locking minimizes loosening caused by vibration
Designed for frequent start-stop operation	Withstands sustained low-speed, high-torque operating conditions

Learn More – 9 Common Output Shaft Types

3. Why don't pellet stove motors use D-type shafts?

D-type shafts rely entirely on the motor’s rotation to drive the output shaft, heavily depending on friction. In high-temperature and high-vibration environments, they are prone to loosening. Long-term use causes wear on the shaft surface and the top end of the output shaft, ultimately leading to machine failure.

4. Maintenance Convenience

For maintenance personnel, this design offers another distinct advantage: the combination of a perforated shaft and pins facilitates easy maintenance and installation.
• During disassembly, only the pins and fixed screws need to be removed.
• There is no need to deal with rusted or seized threads.
• Damage to the motor shaft is minimized.

This design has gained recognition from pellet stove manufacturers worldwide.

Conclusion:

The perforated shaft is used in pellet stove motors to ensure stable operation under high temperature and high torque conditions, and to facilitate subsequent maintenance. For more information about pellet stove motors, please contact us for details.