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- Choose a gear by pitch, # of teeth, or bore size.
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TECHNICAL INFORMATION OF MITER GEARS

Characteristics

Miter gears are a special class of bevel gears where the shafts intersect at 90 degrees and the gear ratio is 1:1. KHK stock miter gears are available in two types, spiral and straight tooth, with high precision grade for demanding torques and speeds, and commercial grade for economical applications. The following table lists the main features for easy selection.

 

[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.

We use Crowning method for gear cutting

KHK utilizes Gleason Coniflex No.104, 102 and 114 bevel gear generating machinery, also equipped for mass production of straight miter gears. You can count on a stable supply of economically priced straight miter gears from KHK.
We use Crowning method for gear cutting_1

We use Crowning method for gear cutting_2

We use Crowning method for gear cutting_3
Gleason Coniflex No.104

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

Among KHK stock miter gears, there are products which are not interchangeable even when the module and the number of teeth are the same. Also, spiral miter gears require additional consideration since the right-hand mates with the left-hand spiral as shown in the table below.

Straight Miter
Straight Miter

Zerol Miter Gears
SMZG products are not interchangeable with products in
other series.

Spiral Miter
Spiral Miter

[CAUTION] For selecting items in the “Allowable in certain cases” category, please reconfirm with your nearest KHK dealer that the pair can work.
Caution in Selecting the Mating Gears

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 the strength calculations, 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

 

Calculation assumptions for Surface Durability (Except those in common with bending strength)

[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. The units for the number of rotations (rpm) and the the stress (kgf/mm2) 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] The values of the allowable bending stresses for DM m1.5 and the allowable root bending stress for LM gears are our own estimates.

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
E-mail info@khkgears.net

1. Caution on Performing Secondary Operations

  1. If you are reboring, it is important to pay special attention to locating the center in order to avoid runout.
  2. 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.
  3. 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.
    Caution on Performing Secondary Operations_1
  4. For items with induction hardened teeth, such as SMSG and SMS series, the hardness is high near the tooth root. When machining the front face, the machined area should be 4 to 6mm smaller than the dimension, J.
    Caution on Performing Secondary Operations_2
  5. 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.
  6. PM plastic miter gears are susceptible to changes due to temperature and humidity. Dimensions may change between during and after remachining operations.
  7. When heat-treating S45C products, it is possible to get thermal stress cracks. It is best to subject them to penetrant inspection afterwards. If tooth strength is not sufficient, it can be increased approximately four times by heat-treating. On the other hand, the precision of the gear will drop about one grade.

2. Points of Caution in Assembling

  1. Since miter gears are cone shaped, they produce axial thrust forces. Specifically with regard to spiral miter gears, the directions of thrust change 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 more technical information, please see the section “Gear Forces” (Page 107) of separate technical reference book.
    Points of Caution in Assembling_1
  2. If a miter 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 miter 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.
    Points of Caution in Assembling_2
  3. Due to the thrust load of miter gears, the gears, shafts and bearings have the tendency to loosen up during operation. Miter gears should be fastened to the shaft with keys and set screws, taper pins, step shafts, etc.
  4. When installing MMSA or MMSB finished bore spiral miter 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 Assembling_3
  5. KHK stock miter gears are designed such that, when assembled according to the specified mounting distance with a tolerance of H7 to H8, the backlash shown in the table are obtained. Mounting distance error, offset error and shaft angle error must be minimized to avoid excessive noise and wear. Inaccurate assembly will lead to irregular noises and uneven wear. Various conditions of teeth contact are shown below.

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

Application Examples

Automatic packaging machine (Miter gears inset)
Automatic packaging machine (Miter gears – inset)

Electric components assembly line (Miter gears SM and PM )
Electric components assembly line (Miter gears <SM and PM>)

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