3MOD, 20 Tooth Left Handed Helical Gear, 15mm Bore, 25mm Face Width - Plastic - POM Description
The 3MOD, 20 Tooth Left Handed Helical Gear, 15mm Bore, 25mm Face Width - Plastic - POM has the following features:
- Bore Diameter (B): 15 mm
- Colour: Blue
- Face Width (FW): 25 mm
- Handedness: Left Handed
- Helix Angle: 45 Degrees
- Hub Diameter (H): 60 mm
- Hub Length: 18 mm
- Plastic - POM
- Plastic Material Family
- Acetal / Polyoxymethylene Material Specification
- Mating Gears: Compatible Mating Gears.
- Number of Teeth: 20
- Outside Diameter (OD): 90.9 mm
- Overall Length (W): 43 mm
- Pitch: 3 MOD
- Pitch Circle Dia. (PCD): 84.85 mm
- Pressure Angle: 20 Degrees
- Weight: 260.3 g
Discover more about the Helical Gears range.
Helical gears, sometimes called helix gears or spiral gears, are precision-cut gears that use helically angled teeth, which mesh gradually for a smoother, quieter transmission compared to traditional straight-tooth spur gears. The inclined tooth form increases the contact ratio, improving load distribution and efficiency, while generating an axial thrust that must be supported by suitable shaft bearings.
Physically, they are cylindrical gears with teeth cut along a helix around the pitch cylinder. Typical features include a defined helix angle, pressure angle and tooth face width, plus a machined hub and bore for accurate mounting.
How Helical Gears Work
When two helical gears engage, their angled teeth slide into contact progressively across the tooth face. This rolling contact reduces noise and vibration, enables higher speeds and supports greater torque transfer compared with spur equivalents.
In practice, engineers choose helical gearing for applications where smooth operation and reliability are critical, such as a compact conveyor drive that requires a 1:2 reduction and operates quietly on a production line for extended shifts with minimal downtime.
Materials Helical Gears Are Made From
Accu’s selection includes materials chosen to optimise wear performance, corrosion resistance and load capacity.
- Stainless Steel (440): High strength and hardness with good corrosion resistance; suited to harsh environments where dimensional stability and longevity matter.
- Steel (C45): A versatile medium-carbon steel offering strong, reliable performance and good machinability for general-purpose power transmission.
Sizes and Types of Helical Gears Available
Our range of helical gears spans 15 to 45 teeth to tune torque and speed. Standard gear ratios from 1:1.5 to 1:3 provide flexible reduction options for compact drives. To suit your layout constraints, we cover assembly distances from 21.8 mm to 75.27 mm, with H7 bores from 6 mm to 16 mm for accurate, repeatable fits. For the best results, select the combination that delivers the centre distance, ratio and shaft fit your project demands.
FAQs
Q: What are some helical gear advantages and disadvantages?
A: Advantages include smoother, quieter operation, higher load carrying capacity from an increased contact ratio and suitability for high speeds with good power density. Disadvantages include axial thrust that demands suitable bearings, more sliding friction than spur gears (especially at light loads) and higher manufacturing and alignment complexity, which can increase cost.
Q: Are helical gears better than spur gears?
A: Compared to spur gears, they’re better where smooth, quiet running and higher load capacity are priorities. Helical teeth engage progressively, reducing noise and shock loading. Spur gears can be more cost effective at low speeds and are simpler to mount because they don’t create axial thrust.
Q: Do helical gears last longer?
A: In comparison to straight tooth gears, yes. The increased contact ratio spreads the load across more tooth area, which can reduce wear, provided alignment, bearing support and lubrication are correct.
Q: Can you run helical gears backwards?
A: Yes. Helical gears transmit power in either direction, but axial thrust reverses direction when the drive reverses. Ensure bearings and housings are specified to handle thrust in both directions.
Q: Do helical gears need lubrication?
A: Absolutely. Lubrication minimises friction and wear on the sliding tooth surfaces, manages heat and helps prevent micropitting.
