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Helical Gears Internal Gears - Technical Data

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Internal gears are offered in modules 0.5 to 3 in 50 to 200 teeth. They can be used in many applications including planetary gear drives.

Features of helical gears - data table
NOTE 1. The product accuracy class having a module less than 0.8 corresponds to ‘equivalent’ as shown in the table.

Application Examples

Internal gears are used to reduce the size of various equipment, such as reduction gears.

Design example of reduction gear
(not a design for machinery or a device in actual use)

Planetary Gear Mechanism used in a reduction gear - Image Example

Mechanical Paradox Gear Mechanism used in a Large Reduction Gear - Image Example

• Example of combinations

Calculation of bending strength of gears - table
Types of planetary gear reduction mechanism

Selection Hints

Please select the most suitable products by carefully considering the characteristics of items and contents of the product tables.

1. Products not listed in this catalog or materials, modules, number of teeth and the like not listed in the dimensional tables can be manufactured as custom items.

Caution when selecting the mating gears

Internal gears can mate with any spur gears of the same module; however, there are cases of involute, trochoid and trimming interference occurrences, depending on the number of teeth of the mating gear. The table below contains the assumptions established for these prod-ucts in order to compute gear strengths.

Interferences and the symptoms

Intereferences and the symptoms - table

Allowable mating pinions and number of teeth

Allowable mating pinions and number of teeth - table

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. We recommend that each user computes their own values by applying the actual usage conditions. The table below contains the assumptions established for various products in order to compute gear strengths.

Calculation of bending strength of gears

Calculation of bending strength of internal gears - table

Calculation of surface durability

Except where it is common with bending strength
Calculation of surface durability, except where it is common with bending strength - table
Note 1 The gear strength formula is based on JGMA (Japanese Gear Manufacturers Association) specifications.The units for the rotational speed (rpm) and 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 JGMA401-01, 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.

Application Hints
In order to use KHK stock gears safely, carefully read the Application Hints before proceeding.
Please refer to Caution on handling and Caution on starting.

If there are questions or you require clarifications, please contact our technical department or your nearest distributor. TEL: (646) 396-GEAR FAX: (516) 437-6700 E-mail: qtcsupport@qtcgears.com

Caution on Performing Secondary Operations

1. If performing outer diameter machining, it is important to pay special attention to locating the center in order to avoid runout.

2. Please exercise caution not to apply too much pressure when chucking the outer diameter. Gear precision may deteriorate and cause trouble.

3. To avoid problems of reduced gear precision and other manufacturing difficulties, do not attempt to machine the gears to reduce face widths.

Points of Caution during Assembly

1. KHK stock internal gears are designed to give the proper normal direction backlash when assembled using the center distance given by the formula below. The amount of backlash is given in the product table for each gear.

Center distance of internal gears - Image

2. Note that the direction of rotation of the internal gear is different from that of two spur gears in mesh.

Gear ratio and direction of rotation

3. To use as a planetary gear drive, the following conditions must be satisfied.

Gear tooth conditions for planetary gear mechanisms

Gear tooth conditions for planetary gear mechanisms - image
KHK considers safety a priority in the use of our products. When handling, adding secondary operations, assembling, and operating KHK products, please be aware of the following issues in order to prevent accidents.

Warning: Precautions for preventing physical and property damagePrecautions for preventing physical and property damage

1. When using KHK products, follow relevant safety regulations (Occupational Safety and Health Regulations, etc.).

2. Pay attention to the following items when installing, removing, or performing maintenance and inspection of the product.
  • Turn off the power switch.
  • Do not reach or crawl under the product.
  • Wear appropriate clothing and protective equipment for the work.

Caution in preventing accidentsCautions in preventing accidents

1. Before using a KHK product, read the precautions in the catalog carefully in order to use it correctly.

2. Avoid use in environments that may adversely affect the product.

3. Our products are manufactured under a superior quality control system based on the ISO9000 quality management system; if you notice any malfunctions upon purchasing a product, please contact the supplier.