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"Easy" Gear Selection Screen

- Choose a gear by pitch, # of teeth, or bore size.
- 2D/3D Drawings Available
- PDF Catalog Available
- Strength Calculation Available

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Technical Information of Bevel Gears


KHK stock bevel gears are available in two types, spiral and straight tooth, in gear ratios of 1.5 through 5, and are offered in a large variety of modules, numbers of teeth, materials and styles. The following table lists the main features for easy selection.

Type : Hypoid Gear


Type : Spiral bevel gears


Type : Zerol Bevel Gears


Type : Straight bevel gears

[NOTE 1] Although these are carburized products, secondary operations can be performed as the bore and the hub portions are masked during the carburization. However, as a precaution, high hardness (HRC40 at maximum) occurs in some cases.

For safe handling and to prevent damage such as deformation, KHK stock bevel gears have round chamfering at the corners, on the top surface plane of a gear tooth.

The chamfering of the corner gear tips for bevel gear
The chamfering of the corner gear tips for bevel gear

Integrated combination of cutting-edge technologies and know-how.

The popularity in our large selection of product lineups is established by a production system integrated with advanced manufacturing technology and know-how, achieving quality products.

Gear cutting of Straight Bevel Gears
Gear cutting of Straight Bevel Gears

Bevel Gear Grinding Machine (Gleason PH 275HG)
Bevel Gear Grinding Machine (Gleason PH-275HG)

Gear cutting of Spiral Bevel Gears
Gear cutting of Spiral Bevel Gears

Bevel Gear Cutting Machine Equipments
Bevel Gear Cutting Machine Equipments

Inspection Equipment
Inspection Equipment


Selection Hints

Please select the most suitable products by carefully considering the characteristics of items and contents of the product tables. It is also important to read all applicable “CAUTION” notes shown below before the final selection.

  1. Caution in Selecting the Mating Gears

    Basically, KHK stock bevel gears should be selected as shown in the catalog in pairs (e.g. MBSG2-4020R should mate with MBSG2-2040L). But, for straight tooth bevel gears, there is some interchangeability with different series. For plastic bevel gears, we recommend metal mating gears for good heat conductivity.

    Caution in Selecting the Mating Gears

    Selection Chart for Straight Bevel Gears
    Selection Chart for Straight Bevel Gears
    Selection Chart for Spiral Bevel Gears
    Selection Chart for Spiral Bevel Gears
    Zerol Bevel Gears
    SBZG products are not interchangeable with products in other series.

  2. Caution in Selecting Gears Based on Gear Strength

    The gear strength values shown in the product pages were computed by assuming a certain application environment. Therefore, they should be used as reference only. We recommend that each user computes their own values by applying the actual usage conditions. To learn more about strength calculation, please refer to the technical information contained in the “Bending Strength of Bevel Gears” section on Page 87, and the “Surface Durability of Bevel Gears” section on Page 93.

    Calculation assumptions for Bending Strength of Gears
    Formula-Note1 : Formula of bevel gears on bending strength (JGMA403-01)
    No. of teeth of mating gear : No. of teeth of the mating gear of the set
    Rotation : 100rpm (600rpm for MBSG, SBSG and SBZG)
    Durability : Over 10^7cycles
    Impact from motor : Uniform load
    Impact from load : Uniform load
    Direction of load : Bidirectional
    Allowable bending stress at root σFlim (kgf/mm^2)-NOTE 2
    : 47 / 47 / 47 / 21 / 21 / 21 / 19(24.5) / 19(24.5) / 10.5
    Safety factor KR : 1.2
    PB / DB
    Formula-Note1 : The Lewis formula
    No. of teeth of mating gear : –
    Rotation : 100rpm
    Durability : –
    Allowable bending stress (kgf/mm^2)
    : 1.15 (40 deg C with No Lubrication) /
    m 0.5 4.0 / m 0.8 4.0 / m 1.0 3.5 (40 deg C with Grease Lubrication)

    Calculation assumptions for Surface Durability (Except those in common with bending strength)
    Formula-NOTE 1 : Formula of bevel gears on surface durability (JGMA404-01)
    Kinematic viscosity of lubricant : 100cSt (50 deg C)
    Gear support : Shafts & gear box have normal stiffness, and gears are supported on one end
    Allowable Hertz stress σFlim (kgf/mm^2)
    : 166 / 166 / 166 / 90 / 90 / 90 / 49(62.5) / 49(62.5) /41.3
    Safety factor CR : 1.15
    [NOTE 1] The gear strength formula is based on JGMA (Japanese Gear Manufacturers Association) specifications. “MC Nylon Technical Data” by Nippon Polypenco Limited and “Duracon Gear Data” by Polyplastic Co. Also, the units (rpm) of number of rotations and unit (kgf/mm^2) of stress are adjusted to the units needed in the formula.
    [NOTE 2] The allowable bending stress at the root σFlim is calculated from JGMA403-01, and set to 2/3 of the value in the consideration of the use of planetary-, idler-, or other gear systems, loaded in both directions.
    [NOTE 3] Since SB Bevel Pinion Shafts are thermally refined, the allowable tooth-root bending stress and allowable hertz stress are referred to the value shown in parentheses.

Application Hints

In order to use KHK stock gears safely, carefully read the Application Hints before proceeding. If there are questions or you require clarifications, please contact our technical department or your nearest distributor.

KHK Co., Ltd.
PHONE: 81-48-254-1744 FAX: 81-48-254-1765

  1. Caution on Performing Secondary Operations

    a. If you are reboring, it is important to pay special atten- SBY6-6015 220 M10 deep 15 tion to locating the center in order to avoid runout.
    b. The reference datum for gear cutting is the bore. Therefore, it is best to use the bore for locating the center. If it is too difficult to do for small bores, the alternative is to use one spot on the bore and the runout of the side surface.
    c. If reworking using scroll chucks, we recommend the use of new or rebored jaws for improved precision. Please exercise caution not to crush the teeth by applying too much pressure. Any scarring will cause noise during operation.
    lathe operations
    d. For items with induction hardened teeth, such as SBSG and SBS series, the hardness is high near the tooth root. When machining the front end, the machined area should be 4 to 6mm smaller than the dimension, J.
    Caution on Performing Secondary Operations4
    e. For tapping and keyway operations, see the examples given in “1. Caution on Performing Secondary Operations” in KHK Stock Spur Gear section. When cutting keyways, to avoid stress concentration, always leave radii on corners.
    f. B plastic bevel gears are susceptible to changes due to temperature and humidity. Dimensions may change between during and after remachining operations.
    g. When heat treating S45C products, it is possible to get thermal stress cracks. It is best to subject them to penetrant inspection afterwards. While the teeth strength may increase four fold, the precision of the gear will drop approximately one grade.
    h. For the handling conveniences, the SB and SBY series listed below has the tapped holes (180 degrees apart, 2 places) on the holding surface.
    Caution on Performing Secondary Operations8

  2. Points of Caution in Assembling

    a. Since bevel gears are cone shaped, they produce axial thrust forces. Especially for spiral bevel gears, the directions of thrust changes with the hand of spiral and the direction of rotation. This is illustrated below. The bearings must be selected properly to be able to handle these thrust forces. For details, please refer to separate technical reference book, section of “Gear Forces” (Page 108).
    Direction of rotation and thrust force
    [NOTE] Bevel gears with the gear ratio 1.57 or less, produce a thrust force which has the same direction as miter gears. For details, see page 254.

    b. If a bevel gear is mounted on a shaft far from the bearings, the shaft may bend. We recommend mounting bevel gears as close to the bearings as possible. This is especially important since most bevel gears are supported on one end. The bending of shafts will cause abnormal noise and wear, and may even cause fatigue failure of the shafts. Both shafts and bearings must be designed with sufficient strength.
    c. Due to the thrust load of bevel gears, the gears, shafts and bearings have the tendency to loosen up during operation. Bevel gears should be fastened to the shaft with keys and set screws, taper pins, step shafts, etc.
    d. When installing MBSA or MBSB spiral bevel gears in B7 style (ring type), always secure the gears onto the mounting base with taper pins to absorb the rotational loads. It is dangerous to secure with bolts only.
    Points of Caution in Assembling4
    e. KHK stock bevel gears are designed such that, when assembled according to the specified mounting distance with a tolerance of H7 – H8, the backlash shown in the table is obtained. Mounting distance error, offset error and shaft angle error must be minimized to avoid excessive noise and wear. For various conditions of teeth contact, please see the following illustrations, “Correct Tooth Contact” and “Incorrect Tooth Contact”.

    Correct Tooth Contact

    When assembled correctly, the contact will occur on both gears in the middle of the flank and center of face width but somewhat closer to the toe.
    Correct Tooth Contact

    Incorrect Tooth Contact

    Mounting Distance Error
    When the mounting distance of the pinion is incorrect, the contact will occur too high on the flank on one gear and too low on the other.
    Mounting Distance Error
    Offset Error
    When the pinion shaft is offset, the contact surface is near the toe of one gear and near the heel of the other.
    Offset Error
    Shaft Angle Error
    When there is an angular error of shafts, the gears will contact at the toes or heels depending on whether the angle is greater or less than 90°.
    Shaft Angle Error

Application Examples
Bevel Gear Application Examples 1
SB Bevel Gears are used in the automatic line-feeding of a machine part processing machine.

Bevel Gear Application Examples 2
2WD Bicycle by SHESCO
SB Bevel Gears are used in the driving components in both the front and rear wheels.

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