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.

 

  • Type : Spiral Miter Gears
    Catalog No. : MMSG
    Module : 2-4
    No. of Teeth : 20, 25, 30
    Material : SCM415
    Heat Treatment : Carburized Note 1
    Tooth Surface Finish : Ground
    Precision JIS B 1704:1978 : 1
    Secondary Operations : Partly Possible
    Features : High strength, abrasion-resistant and compact for high speed & torque use.
  • Type : Spiral Miter Gears
    Catalog No. : SMSG
    Module : 2-5
    No. of Teeth : 20, 25, 30
    Material : S45C
    Heat Treatment : Gear teeth induction hardened
    Tooth Surface Finish : Ground
    Precision JIS B 1704:1978 : 2
    Secondary Operations : Partly Possible
    Features : Reasonably priced ground gear, yet remachinable except for the gear teeth.
  • Type : Spiral Miter Gears
    Catalog No. : KSP F type
    Module : 1.5-6
    No. of Teeth : 20-30
    Material : SCM415
    Heat Treatment : Carburized
    Tooth Surface Finish : Ground
    Precision JIS B 1704:1978 : 0
    Secondary Operations : Not possible
    Features : Superior performance with regard to high speed, low noise, and low vibration.
  • Type : Spiral Miter Gears
    Catalog No. : KSP U type
    Module : 1.5-6
    No. of Teeth : 20-30
    Material : SCM415
    Heat Treatment : Carburized NOTE 1
    Tooth Surface Finish : Ground
    Precision JIS B 1704:1978 : 0
    Secondary Operations : Partly Possible
    Features : Superior performance with regard to high speed, low noise, and low vibration.
  • Type : Spiral Miter Gears
    Catalog No. : MMSA / MMSB
    Module : 1-10
    No. of Teeth : 20
    Material : SCM415
    Heat Treatment : Carburized
    Tooth Surface Finish : Cut
    Precision JIS B 1704:1978 : 4
    Secondary Operations : Not possible
    Features : Ready to use without performing secondary operations. Strong and abrasion resistant.
  • Type : Spiral Miter Gears
    Catalog No. : MMS
    Module : 2-5
    No. of Teeth : 20, 25, 30
    Material : SCM415
    Heat Treatment : Carburized NOTE 1
    Tooth Surface Finish : Cut
    Precision JIS B 1704:1978 : 4
    Secondary Operations : Partly Possible
    Features : Only teeth are induction hardened, allowing user to perform secondary operations elsewhere.
  • Type : Spiral Miter Gears
    Catalog No. : SMS
    Module : 1-8
    No. of Teeth : 20, 25, 30
    Material : S45C
    Heat Treatment : Gear teeth induction hardened
    Tooth Surface Finish : Cut
    Precision JIS B 1704:1978 : 4
    Secondary Operations : Partly Possible
    Features : Large numbers of teeth and modules are offered in these affordable spiral miter gears.
  • Type : Zerol miter gears
    Catalog No. : SMZG
    Module : 2-3
    No. of Teeth : 20
    Material : S45C
    Heat Treatment : Gear teeth induction hardened
    Tooth Surface Finish : Ground
    Precision JIS B 1704:1978 : 2
    Secondary Operations : Partly Possible
    Features : A spiral miter gear with a helix angle less than 10°. Receives forces from the same direction as straight miter gears receive and have excellent precision properties..
  • Type : Straight Miter Gears
    Catalog No. : SMA / SMB / SMC
    Module : 1-8
    No. of Teeth : 20, 25, 30
    Material : S45C
    Heat Treatment : Gear teeth induction hardened
    Tooth Surface Finish : Cut
    Precision JIS B 1704:1978 : 4
    Secondary Operations : Partly Possible
    Features : Usable without remachining, offered in 3 bore sizes.
  • Type : Straight Miter Gears
    Catalog No. : MM
    Module : 2-5
    No. of Teeth : 20, 25, 30
    Material : SCM415
    Heat Treatment : Carburized Note 1
    Tooth Surface Finish : Cut
    Precision JIS B 1704:1978 : 4
    Secondary Operations : Partly Possible
    Features : Compared to SM miters, these are stronger and less abrasive, and allow secondary operations.
  • Type : Straight Miter Gears
    Catalog No. : LM
    Module : 0.8-1.5
    No. of Teeth : 20
    Material : SMF5040 (Equiv. to S45C)
    Heat Treatment : –
    Tooth Surface Finish : Sintered
    Precision JIS B 1704:1978 : 5
    Secondary Operations : Possible
    Features : Mass-produced, low cost sintered products. Small and light weight.
  • Type : Straight Miter Gears
    Catalog No. : SM
    Module : 1-8
    No. of Teeth : 16, 20, 25, 30
    Material : S45C
    Heat Treatment : –
    Tooth Surface Finish : Cut
    Precision JIS B 1704:1978 : 3
    Secondary Operations : Possible
    Features : Popular straight miter for many uses.
  • Type : Straight Miter Gears
    Catalog No. : SAM
    Module : 1.5-3
    No. of Teeth : 20
    Shaft Angle : 45 Deg, 60 Deg, 120 Deg
    Material : S45C
    Heat Treatment : –
    Tooth Surface Finish : Cut
    Precision JIS B 1704:1978 : 3
    Secondary Operations : Possible
    Features : 3 types are available for shafts at 45 Deg, 60 Deg and 120 Deg.
  • Type : Straight Miter Gears
    Catalog No. : SUM
    Module : 1-4
    No. of Teeth : 20, 25
    Material : SUS303
    Heat Treatment : –
    Tooth Surface Finish : Cut
    Precision JIS B 1704:1978 : 3
    Secondary Operations : Possible
    Features : Suitable for food machinery due to SUS303’s rust-resistant quality.
  • Type : Straight Miter Gears
    Catalog No. : SUMA
    Module : 1-4
    No. of Teeth : 20, 25
    Material : SUS303
    Heat Treatment : –
    Tooth Surface Finish : Cut
    Precision JIS B 1704:1978 : 3
    Secondary Operations : Partly Possible
    Features : Stainless steel products, usable without remachining.
  • Type : Straight Miter Gears
    Catalog No. : PM
    Module : 1-4
    No. of Teeth : 20, 25
    Material : MC901
    Heat Treatment : –
    Tooth Surface Finish : Cut
    Precision JIS B 1704:1978 : 4
    Secondary Operations : Possible
    Features : MC nylon products are light and can be used without lubricant.
  • Type : Straight Miter Gears
    Catalog No. : DM
    Module : 0.5-1.5
    No. of Teeth : 20
    Material : DURACON (M90-44)
    Heat Treatment : –
    Tooth Surface Finish : Injection Molded
    Precision JIS B 1704:1978 : 6
    Secondary Operations : Partly Possible
    Features : Injection molded, mass-produced products, suitable for office machines.

[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

  • Catalog No. : MMSG / MMSA / MMSB / MMS / MM
    Formula NOTE 1 : Formula of bevel gears on bending strength (JGMA403-01)
    No. of teeth of mating gear : Same number of teeth
    Rotation : 100rpm (600rpm for MMSG, SMSG and SMZG)
    Durability : Over 10^7cycles
    Impact from motor : Uniform load
    Impact from load : Uniform load
    Direction of load : Bidirectional
    Allowable bending stresss at root σFlim(kgf/mm^2) NOTE 2 : 47
    Safety factor KR : 1.2
  • Catalog No. : SMSG / SMZG / SMS / SMA / SMB / SMC
    Formula NOTE 1 : Formula of bevel gears on bending strength (JGMA403-01)
    No. of teeth of mating gear : Same number of teeth
    Rotation : 100rpm (600rpm for MMSG, SMSG and SMZG)
    Durability : Over 10^7cycles
    Impact from motor : Uniform load
    Impact from load : Uniform load
    Direction of load : Bidirectional
    Allowable bending stresss at root σFlim(kgf/mm^2) NOTE 2 : 21
    Safety factor KR : 1.2
  • Catalog No. : SM / SAM
    Formula NOTE 1 : Formula of bevel gears on bending strength (JGMA403-01)
    No. of teeth of mating gear : Same number of teeth
    Rotation : 100rpm (600rpm for MMSG, SMSG and SMZG)
    Durability : Over 10^7cycles
    Impact from motor : Uniform load
    Impact from load : Uniform load
    Direction of load : Bidirectional
    Allowable bending stresss at root σFlim(kgf/mm^2) NOTE 2 : 19
    Safety factor KR : 1.2
  • Catalog No. : SUM / SUMA / LM NOTE 3
    Formula NOTE 1 : Formula of bevel gears on bending strength (JGMA403-01)
    No. of teeth of mating gear : Same number of teeth
    Rotation : 100rpm (600rpm for MMSG, SMSG and SMZG)
    Durability : Over 10^7cycles
    Impact from motor : Uniform load
    Impact from load : Uniform load
    Direction of load : Bidirectional
    Allowable bending stresss at root σFlim(kgf/mm^2) NOTE 2 : 10.5
    Safety factor KR : 1.2
  • Catalog No. : PM
    Formula NOTE 1 : 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)
  • Catalog No. : DM
    Formula NOTE 1 : The Lewis formula
    No. of teeth of mating gear : –
    Rotation : 100rpm
    Durability : –
    Allowable bending stress (kgf/mm^2) : m 0.8 4.0 / m 1.0 3.5 / m 1.5 1.8 NOTE 3 (40 Deg C with Grease Lubrication)

 

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

  • Catalog No. : MMSG / MMSA / MMSB / MMS / MM
    Formula NOTE 1 : Formula of bevel gears on bending strength (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 σHlim (kgf/mm^2) : 166
    Safety factor CR : 1.15
  • Catalog No. : SMSG / SMZG / SMS / SMA / SMB / SMC
    Formula NOTE 1 : Formula of bevel gears on bending strength (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 σHlim (kgf/mm^2) : 90
    Safety factor CR : 1.15
  • Catalog No. : SM / SAM
    Formula NOTE 1 : Formula of bevel gears on bending strength (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 σHlim (kgf/mm^2) : 49
    Safety factor CR : 1.15
  • Catalog No. : SUM / SUMA / LM NOTE3
    Formula NOTE 1 : Formula of bevel gears on bending strength (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 σHlim (kgf/mm^2) : 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. 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

  • 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 Deg.
    Shaft Angle Error

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>)