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Straight Bevel Gears

Straight Bevel Gear produced by Arrow Gear
Straight tooth bevel gear

As their name suggests, Straight Bevel Gears have a straight tooth geometry, which if extended, would pass through the point of intersection of their axes.  

These are the simplest form of bevel gear. Like spur gears, the teeth on a straight bevel gear are straight, but they taper from the large diameter of the gear tooth (the heel) to the small diameter (the toe).

Crowning on a straight tooth bevel from Coniflex cuttingr
Fig.1 - Crowning on the tooth of a straight tooth bevel gear from the Coniflex cutting process

There are two main methods for cutting straight bevel gear teeth; shaping and Coniflex cutting. Straight bevel gear teeth cut in a shaping machine results in teeth that are precisely straight. However, pure straight teeth are not desirable for many applications because they do not allow for any misalignment when the gears are assembled in a gear box. In view of this, the preferred method for cutting straight bevel gears actually puts a small amount of curvature, called crowning, on the teeth. This curvature results in a barrel shaped tooth that allows for some misalignment. See Figure 1. This type of straight bevel gear is called a Coniflex after the manufacturing process that produces it. In Coniflex cutting, two cutters interlace while rolling through the tooth slot during the cutting process. See Figure 2.

Coniflex Cutting of Straight Bevel Gear
Fig.2 - Coniflex cutting of a straight bevel gear

The Coniflex process is very fast, but needs to have space in front of the part for the cutter. When this is not possible due to the geometry of the part, the shaping process can be used. The shaping process also uses two cutters which reciprocate through the tooth slot as they roll through. While this process is versatile, it is considerably slower than Coniflex cutting, so it is used as needed.

Arrow’s size range and capabilities for Straight Bevel Gears are provided in the list below.

Maximum Pitch Diameter – 28”
Diametral Pitch – 2.5 – 48
Face Width – 6.0
Unground Tooth – AGMA Q9

Straight Bevel Gear Teeth produced by Arrow Gear
Straight bevel gear and pinion in mesh