The ideal helix angle for your helical gears depends on your specific application, but angles between 15° and 30° are typically optimal.
You’ll want to consider factors like load capacity, operational noise, and efficiency when selecting the angle. Higher angles offer quieter operation and better load distribution, while lower angles provide higher strength.
Can Helical Gears Be Used at Any Angle
While helical gears offer greater flexibility in the allowable angles between shafts compared to spur gears, they cannot be used at absolutely any angle. Helical gears are limited to shaft angles that fall within a certain range, typically up to 90°, though in some specialized applications angles up to 120° may be possible.
What Is The Best Angle For Helical Gears
Helix angle
The helix angle is the angle at which the teeth of a helical gear are cut relative to the gear’s axis of rotation. This angle is measured in the axial plane and is typically expressed in degrees.
In single-helical gears, the helix angle commonly ranges from 12° to 20°.
Double-helical gears, also known as herringbone gears, feature two sets of helical teeth with opposite handedness. The helix angles in double-helical gears are typically higher, ranging from 20° to 45°.
Shaft angle
The shaft angle refers to the angle between the axes of rotation of two meshing helical gears.
When the shaft angle is 0°, the helical gears are mounted on parallel shafts, similar to spur gears.
Non-parallel shaft arrangements, with shaft angles greater than 0°, enable helical gears to transmit power between intersecting or skewed shafts. The most common non-parallel configuration is the 90° shaft angle, which allows for power transmission between perpendicular shafts.
Pressure angle
The pressure angle is the angle between the line of action (the direction of the force transmitted between gears) and the tangent to the pitch circle (the imaginary circle that rolls without slipping between mating gears).
Standard pressure angles for helical gears are 14.5°, 20°, and 25°.
- The 20° pressure angle is the most commonly used, as it provides a good balance between gear strength and efficiency.
- Gears with a 14.5° pressure angle have longer, more slender teeth, which can be advantageous in applications requiring higher contact ratios or lower backlash.
- The 25° pressure angle results in shorter, thicker teeth, making the gears more suitable for high-load applications where increased tooth strength is necessary.
Helical Gear Angle Formula
The formula for calculating the optimum helix angle (β) is:
β = arctan(C / (π * m * z))
Where:
- C is the helix factor, which typically ranges from 25 to 30 for helical gears
- m is the gear module (mm)
- z is the number of teeth on the gear
For example, let’s calculate the optimum helix angle for a gear with a helix factor of 28, a module of 3 mm, and 50 teeth:
β = arctan(28 / (π * 3 * 50)) β ≈ 0.1069 radians β ≈ 6.13 degrees
In this case, the optimum helix angle for the given gear parameters is approximately 6.13 degrees.
