GB/T 12370-2025 Bevel and hypoid gears - Terminology English, Anglais, Englisch, Inglés, えいご
This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation, self-check, revision and verification) will be delivered upon being ordered.
ICS 13.220.10
CCS H 57
National Standard of the People's Republic of China
GB/T 12370-2025
Replaces GB/T 12370-1990
Bevel and hypoid gears - Terminology
锥齿轮和准双曲面齿轮 术语
Issue date: 2025-10-31 Implementation date: 2026-05-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
1 Scope
2 Normative References
3 Kinematics and Geometry
3.1 Kinematics
3.2 Tooth Characteristics
3.3 Geometry
3.4 Meshing and Modification
4 Classification of Bevel and Hypoid Gears
4.1 Classification by Gear Shape and Axis Relationship
4.2 Classification by Tooth Line Shape
4.3 Tooth Contraction
4.4 Tooth Height Contraction
5 Points, Curves, and Surfaces
5.1 Apex, Intersection Point
5.2 Circle
5.3 Surface
6 Basic Dimensional Parameters
6.1 Cone Distance
6.2 Diameter
6.3 Tooth Height
6.4 Tooth Pitch, Tooth Thickness, and Tooth Width
6.5 Other Linear Parameters
6.6 Cone Angle
6.7 Other Angular Parameters
7 Design and Adjustment Calculations
7.1 Length
7.2 Angle
7.3 Others
8 Processing Methods and Equipment, Tooth Contact, Inspection, and Testing
8.1 Processing Methods and Equipment
8.2 Tooth Contact
8.3 Inspection and Testing
References
Index
1 Scope
This document defines common terms and definitions for bevel and hypoid gears, encompassing kinematics and geometry, classification of bevel and hypoid gears, points, curves and surfaces, basic dimensional parameters, design and adjustment calculations, processing methods and equipment, tooth contact, inspection and testing, among other terminologies.
This document is applicable to technical documents and work communications involving bevel and hypoid gears.
Note: Unless otherwise specified, the term "bevel gear" in this document generally refers to both "bevel gears and hypoid gears".
2 Normative references
This document has no normative references.
3 Kinematics and geometry
3.1 Kinematics
3.1.1
Gear pair with intersecting axes
A gear pair where the two axes intersect.
Note: See Figure 1.
3.1.2
Gear pair with crossing axes
Offset axes gear pair
A gear pair where the two axes are neither parallel nor intersecting.
Note: See Figure 2.
3.1.3
Basic tooth profile
The imaginary tooth profile of an octoid crown gear in the normal plane at the large end.
3.1.4
Tooth profile of octoid gear
The tooth profile of a bevel gear whose line of contact is a space curve forming an "8" shape on a spherical surface.
Note: See Figure 3.
3.1.5
Octoid crown gear
A bevel gear with a pitch cone angle equal to 90°, a straight-line tooth profile, and a line of contact forming a spherical "8" shape.
3.1.6
Generating gear of a gear
The imaginary gear used to design or generate (form) bevel gears.
Note: See Figure 4.
3.1.8
Tooth trace
The intersection line of the tooth surface and the pitch cone surface.
3.2 Tooth characteristics
3.2.1
Right-hand teeth
For spiral bevel gears, when the observer looks from the apex towards the large end, the back cone tooth profile on the tooth is rotated clockwise relative to the tooth profile on the mean cone surface by an angle.
Note: See Figure 5.
3.2.2
Left-hand teeth
For spiral bevel gears, when the observer looks from the apex towards the large end, the back cone tooth profile on the tooth is rotated counterclockwise relative to the tooth profile on the mean cone surface by an angle.
Note: See Figure 6.
3.2.3
Concave side; concave flank
The tooth surface which is concave in the lengthwise direction, cut by the blades on the outside of the cutter head.
Note:See Figure 7.
3.2.4
Convex side; convex flank
The tooth surface which is convex in the lengthwise direction, cut by the blades on the inside of the cutter head.
Note: See Figure 8.
3.2.5
Drive side
The tooth surfaces that come into mesh and contact between the pinion and gear when the vehicle (machine) is in forward drive or the majority of working conditions.
Note: Under general conditions, the pinion is the driving gear (meshing on the concave side), and the gear is the driven gear (meshing on the convex side).
3.2.6
Coast side
The tooth surfaces that come into mesh and contact between the pinion and gear when the vehicle (machine) is in reverse drive.
3.2.7
Back cone tooth profile
The intersection curve where the tooth surface of a bevel gear is cut by the back cone.
Note: See Figure 9.
3.3 Geometry
3.3.1
Prolate epicycloid
Extended epicycloid
On a plane, when a moving circle (generating circle) rolls externally and purely on the outside of a fixed circle (base circle), the trajectory of a point that is fixed to the moving circle and located outside the moving circle.
Note: See Figure 10.
3.3.2
Spherical involute
When a great circle (generating circle) on a sphere rolls purely on a fixed small circle (base circle) located on the same sphere, the movement trajectory on the sphere of an arbitrary point located on the great circle.
Note: See Figure 11.
3.4 Meshing and modification
Standard
GB/T 12370-2025 Bevel and hypoid gears - Terminology (English Version)
GB/T 12370-2025 Bevel and hypoid gears - Terminology English, Anglais, Englisch, Inglés, えいご
This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation, self-check, revision and verification) will be delivered upon being ordered.
ICS 13.220.10
CCS H 57
National Standard of the People's Republic of China
GB/T 12370-2025
Replaces GB/T 12370-1990
Bevel and hypoid gears - Terminology
锥齿轮和准双曲面齿轮 术语
Issue date: 2025-10-31 Implementation date: 2026-05-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
1 Scope
2 Normative References
3 Kinematics and Geometry
3.1 Kinematics
3.2 Tooth Characteristics
3.3 Geometry
3.4 Meshing and Modification
4 Classification of Bevel and Hypoid Gears
4.1 Classification by Gear Shape and Axis Relationship
4.2 Classification by Tooth Line Shape
4.3 Tooth Contraction
4.4 Tooth Height Contraction
5 Points, Curves, and Surfaces
5.1 Apex, Intersection Point
5.2 Circle
5.3 Surface
6 Basic Dimensional Parameters
6.1 Cone Distance
6.2 Diameter
6.3 Tooth Height
6.4 Tooth Pitch, Tooth Thickness, and Tooth Width
6.5 Other Linear Parameters
6.6 Cone Angle
6.7 Other Angular Parameters
7 Design and Adjustment Calculations
7.1 Length
7.2 Angle
7.3 Others
8 Processing Methods and Equipment, Tooth Contact, Inspection, and Testing
8.1 Processing Methods and Equipment
8.2 Tooth Contact
8.3 Inspection and Testing
References
Index
1 Scope
This document defines common terms and definitions for bevel and hypoid gears, encompassing kinematics and geometry, classification of bevel and hypoid gears, points, curves and surfaces, basic dimensional parameters, design and adjustment calculations, processing methods and equipment, tooth contact, inspection and testing, among other terminologies.
This document is applicable to technical documents and work communications involving bevel and hypoid gears.
Note: Unless otherwise specified, the term "bevel gear" in this document generally refers to both "bevel gears and hypoid gears".
2 Normative references
This document has no normative references.
3 Kinematics and geometry
3.1 Kinematics
3.1.1
Gear pair with intersecting axes
A gear pair where the two axes intersect.
Note: See Figure 1.
3.1.2
Gear pair with crossing axes
Offset axes gear pair
A gear pair where the two axes are neither parallel nor intersecting.
Note: See Figure 2.
3.1.3
Basic tooth profile
The imaginary tooth profile of an octoid crown gear in the normal plane at the large end.
3.1.4
Tooth profile of octoid gear
The tooth profile of a bevel gear whose line of contact is a space curve forming an "8" shape on a spherical surface.
Note: See Figure 3.
3.1.5
Octoid crown gear
A bevel gear with a pitch cone angle equal to 90°, a straight-line tooth profile, and a line of contact forming a spherical "8" shape.
3.1.6
Generating gear of a gear
The imaginary gear used to design or generate (form) bevel gears.
Note: See Figure 4.
3.1.8
Tooth trace
The intersection line of the tooth surface and the pitch cone surface.
3.2 Tooth characteristics
3.2.1
Right-hand teeth
For spiral bevel gears, when the observer looks from the apex towards the large end, the back cone tooth profile on the tooth is rotated clockwise relative to the tooth profile on the mean cone surface by an angle.
Note: See Figure 5.
3.2.2
Left-hand teeth
For spiral bevel gears, when the observer looks from the apex towards the large end, the back cone tooth profile on the tooth is rotated counterclockwise relative to the tooth profile on the mean cone surface by an angle.
Note: See Figure 6.
3.2.3
Concave side; concave flank
The tooth surface which is concave in the lengthwise direction, cut by the blades on the outside of the cutter head.
Note:See Figure 7.
3.2.4
Convex side; convex flank
The tooth surface which is convex in the lengthwise direction, cut by the blades on the inside of the cutter head.
Note: See Figure 8.
3.2.5
Drive side
The tooth surfaces that come into mesh and contact between the pinion and gear when the vehicle (machine) is in forward drive or the majority of working conditions.
Note: Under general conditions, the pinion is the driving gear (meshing on the concave side), and the gear is the driven gear (meshing on the convex side).
3.2.6
Coast side
The tooth surfaces that come into mesh and contact between the pinion and gear when the vehicle (machine) is in reverse drive.
3.2.7
Back cone tooth profile
The intersection curve where the tooth surface of a bevel gear is cut by the back cone.
Note: See Figure 9.
3.3 Geometry
3.3.1
Prolate epicycloid
Extended epicycloid
On a plane, when a moving circle (generating circle) rolls externally and purely on the outside of a fixed circle (base circle), the trajectory of a point that is fixed to the moving circle and located outside the moving circle.
Note: See Figure 10.
3.3.2
Spherical involute
When a great circle (generating circle) on a sphere rolls purely on a fixed small circle (base circle) located on the same sphere, the movement trajectory on the sphere of an arbitrary point located on the great circle.
Note: See Figure 11.
3.4 Meshing and modification
