Most Avon bearings are equipped with integral gearing. The material used in the bearing rings is well suited for high strength gearing. Virtually any configuration of gearing can be provided. The most popular tooth forms are 20° stub, full depth and module.

Most designers prefer the stub tooth for low speed, intermittently rotated applications. The stub tooth provides greater beam strength than the full depth and module tooth.

For continuously operating applications, particularly with higher speed, the full depth tooth form provides the advantage of higher contact ratio, resulting in somewhat smoother, quieter operation and greater resistance to fatigue failure of the tooth surfaces.

Internal and external gears can be cut to precision levels meeting AGMA Class 10.

Gear Hardness
Avon Series M as well as a few series H, T and R bearings are produced with normalized rings providing gear tooth hardness in the range of 180-248 BHN. Nearly all other Avon bearings utilize heat treated rings, mostly with core hardness of 248-302BHN. A few are produced with core hardness ranges of 285-321BHN. This latter value is the greatest hardness which can be conveniently and economically cut with standard gear cutting equipment. (The term core hardness is used to differentiate from raceway hardness, which is produced by secondary hardening operations.)

For heavily loaded equipment which has a high rotational speed, the bearing gear can be provided with a secondary heat treating on the surface, typically producing surface hardness of approximately 55 Rc. The surface hardening increases the gear capacity from a standpoint of surface endurance and is desirable in high duty cycle applications. If the gearing utilizes full root radii and if the surface hardening is uniform throughout the root, there is some increase in the beam strength. As noted above, this high hardness is of no value unless precise gear and pinion alignment is assured and the gearing is protected from heavy shocks. Avon can produce any of the variations in gear profile and metallurgy discussed above

Backlash Allowance
In order to provide for unavoidable dimensional variation, thermal expansion, and lubricant clearance, the teeth in one or both gears in the set are cut somewhat thinner than nominal. This thinning is referred to as "backlash allowance". In the case of high ration gearing, normally only the gear is thinned, while the pinion is kept at nominal thickness in order to maximize its tooth strength. The tooth thickness on geared Avon bearings is specified on outline drawings which are available on request. Please contact Avon Bearing Engineering for assistance in the determination of proper assembled backlash.

Gear Capacity
Tangential tooth force capacity is shown in the dimension tables for each catalog bearing. These capacity values are based on static bending strength according to the Lewis Equation with a bending stress value of 25 percent of ultimate tensile strength. Experience has shown this to be a practical limitation for low speed intermittent operation gear loading. This value should not be exceeded in routine acceleration or deceleration. This rating allows for some reasonable amount of gear misalignment resulting from pinion shaft deflection, etc. When such misalignment exists, some permanent deformation of the gear teeth may result, however not to the extent that it interferes with normal function. Occasional peak loads, up to 200 percent of the rated load, can usually be tolerated, albeit with some additional localized deformation. These gear ratings consider only bending strength. On gear sets which will frequently be exposed to heavy loading fatigue resistance should also be considered. Tooth bending fatigue and surface endurance may be calculated according to procedures published by the American Gear Manufacturers Association (AGE). In order to make meaningful fatigue calculations it is essential to provide a realistic estimate of expected duty cycle showing frequency of operation at various lad levels. It is also essential that the extent of gear misalignment be accurately estimated. It you can provide this data, Avon will be pleased to perform gear fatigue calculations.