Helical Gears

Helical gears are circular gears whose teeth curve along a helical path. Helical-toothed gears transmit power and motion between parallel axes (opposite hand) or right-angle axes (same-hand).  Helical gears may be anti-backlash, meaning they have a mechanical assist such as a spring to take up any play between meshing gear teeth, thus avoiding backlash when gear direction changes.

Important parameters to consider when specifying helical gears include number of teeth, pitch diameter, face or tooth width, and outside diameter.  The number of teeth, along with desired pitch diameter, will dictate the pitch of the gear. The face width is width of the teeth. Gear hand direction and pressure angle are also important to consider.  Helical gears have a right or left hand specification, which describes the direction of tooth curve. Helical gears of opposite hand (one right and one left) will mesh for parallel-axis power transmission. Same-hand pairs will mesh for perpendicular or off-axis power transmission, depending on the helix angle. Gears must have the same pressure angle to mesh.

Other important specifications to consider for helical gears, include materials of construction and mounting.  Materials of construction can be metal or plastic. Gears are made from a wide variety of materials with many different properties. Factors such as design life, power transmission requirements, noise and heat generation, and presence of corrosive elements contribute to optimization of gear material. Consult with a gear manufacturer on a specific application for the best material.  Helical gears, can be mounted on a hub or shaft.  A hub is a cylindrical projection on one or both sides of gear, often for the provision of a screw or other shaft attachment mechanism. Hubless gears are typically attached via press fit, adhesive, or internal keyway.  Shaft mounting choices include keyway, set screws, hub claming screws, split, and simple bore.

• Fundamentals of Helical Gears
  In Figure 5-2 the gear train has a difference of numbers of teeth of only 1; z1 = 30 and z2 = 31. This results in a reduction ratio of 1/30. SECTION 6 HELICAL GEARS The helical gear differs from the...
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• Surface Strength of Spur And Helical Gears
  The following equations can be applied to both spur and helical gears, including double helical and internal gears, used in power transmission. The general range of application is:...
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• Technical Reference: HELICAL GEARS
  The helical gear differs from the spur gear in that its teeth are twisted along a helical path in the axial direction. It resembles the spur gear in the plane of rotation, but in the axial direction...
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Part Numbers for Helical Gears