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HELICAL GEAR

Why Is It So Smooth?
Design Formula Forces Calculation
"The secret is in the angle."
⬇ Swipe to explore
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Definition

What Makes It Different?

Helical gear teeth are cut at an angle to the shaft axis, forming a helix around the gear body.
Angled teeth Gradual engagement Smoother operation
Spur Gear
Straight teeth
Helical Gear
Angled teeth
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Advantages

Why Use Helical Gears?

✓ Smoother operation
✓ Lower noise
✓ Higher load capacity
✓ Good high-speed capability
✓ Versatile power transmission
🔄 More gradual tooth engagement
The angled teeth share load across multiple contact points.
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The Catch

Helical Gears Create Axial Thrust

🔄 Gear rotation → Tooth force → Axial force → Bearing
Angled teeth = axial thrust
The thrust must be considered when selecting bearings.
This is why thrust bearings are essential in helical gearboxes.
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Design Parameter

The Angle Changes Everything

β
Helix Angle
Lower angle Less axial thrust
Higher angle Smoother, more thrust
Typical range: 10° – 45°
15°–30° common in many applications
Range is application-dependent, not a universal rule.
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Core Formula

Normal vs Transverse Module

mt = mn / cos(β)
Transverse module from normal module & helix angle
d = mt × z
Pitch diameter
i = z₂ / z₁
Gear ratio
Reference: AGMA, ISO 6336, DIN 3990
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Worked Example

Can You Calculate This Gear?

Driver z₁ 20 teeth
Driven z₂ 60 teeth
Normal module mₙ 3 mm
Helix angle β 20°
mₜ
3.193 mm
d₁
63.86 mm
d₂
191.58 mm
Center dist.
127.72 mm
3:1 REDUCTION
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Force Analysis

How Much Force?

Tangential
Fₜ = 2T/d
1,879 N
Axial
Fₐ = Fₜ × tan(β)
684 N
Radial
Fᵣ = Fₜ × tan(α) / cos(β)
727 N
"That 684 N must go somewhere…"
→ It goes into the thrust bearing.
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Production

How Is a Helical Gear Made?

⬇ Material selection
⬇ Hobbing
⬇ Shaping / Milling
⬇ Heat Treatment
⬇ Grinding / Finishing
⬇ Inspection
Hobbing Shaping Milling Grinding Broaching
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Applications

You See Them Everywhere

🚗 Automotive
🏭 Industrial gearboxes
🤖 Robotics
✈️ Aerospace
⚙️ Pumps & compressors
📦 Printing & packaging
🔋 Renewable energy
🔧 Consumer machinery
Wherever smooth, high-load power transmission is needed.
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Failure & Maintenance

Why Do Helical Gears Fail?

⚠ Tooth bending
⚠ Pitting & spalling
⚠ Wear
⚠ Misalignment
⚠ Lubrication failure
⚠ Bearing failure
CHECK THE THRUST BEARINGS
✓ Lubrication
✓ Backlash
✓ Alignment
✓ Runout
✓ Tooth condition
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Calculate Your Helical Gear

Enter teeth, normal module, helix angle, face width and torque.
OPEN HELICAL GEAR CALCULATOR READ THE FULL GUIDE →
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Spur Gear Worm Gear Gear Train Bearing Selection
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