Today, Guangming Group shares the core structure and specifications of D-bore helical gears.

Core Structure and Specifications of D-Bore Helical Gear

I. Core Structural Components

1. D-shaped inner bore (core positioning part)

It is formed by milling one flat side of a round hole, which locks the flat section of the transmission shaft without flat keys to prevent slipping.

Structure: Circular wall with one flat positioning edge

Matching method: Interference press-fit as the primary assembly method; heavy-load versions feature threaded set screw holes on the hub for secondary locking reinforcement.

Hub: Thickened cylindrical hub improves the torsional strength of the D-bore and avoids cracking of the bore wall under torque.

As a professional manufacturer and factory based in China, we strictly control the dimensional tolerance of each D-bore to guarantee stable fit performance for global buyers and suppliers.

2. Helical tooth section (core transmission part)

Helical inclined teeth: Teeth are arranged in a spiral angle, divided into left-hand and right-hand types. Mated pairs counteract partial axial thrust during operation.

Standard involute profile for addendum and dedendum

Face width: The working width of meshing teeth, which determines load-bearing capacity

Tooth surface treatment: Quenched carbon steel, integrally molded plastic, polished brass

3. Transition base

The hub and gear ring are integrally formed without splicing to ensure high coaxiality. High-torque customized models adopt an enlarged outer hub diameter and thicker wall thickness.

II. General Standard Specifications

1. Common D-bore dimensions (bore diameter × flat depth)

5×4.5, 6×5.5, 8×7, 8×7.5, 10×9, 12×10.8, 14×12.5

Tolerance: Inner bore H7, matched with h6 shaft for precision clearance or interference fit.

Our factory in China supports custom D-bore sizes for all suppliers with special shaft matching demands.

2. Standard Gear Modules

Micro precision series: 0.3M, 0.5M

General industrial equipment: 0.8M, 1M, 1.5M, 2M

3. Helix Angles

Common standard angles: 15°, 20°, 45°. The 45° version is widely applied for 90° crossed-axis transmission.

4. Tooth Count Range

Micro type: 10 ~ 40 teeth

Industrial transmission type: 40 ~ 80 teeth; custom low/high tooth counts are available from our China manufacturer team.

5. Regular Face Width Sizes

3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 15mm. Wider face width is adopted for higher load conditions.

6. Material Specifications

Light-load plastic type: POM, nylon (low noise, cost-effective, for models and small motors)

Medium-load wear-resistant type: Brass, powder metallurgy

Heavy-duty industrial type: 45# steel, 40Cr with high-frequency quenching on tooth surfaces

We supply full-material options as a one-stop supplier from China factory for all transmission equipment clients.

7. Auxiliary Structural Specifications

Set screw holes: M2, M2.5, M3; tapped on hub side for reinforcement under bidirectional force

Chamfer: C0.5/C1 on both ends of inner bore for easy press-fitting assembly

Counterbore on end face: Customizable shoulder step to limit gear axial mounting position

III. Key Matching Requirements for Structures

Mated gear set must consist of one left-hand and one right-hand helical gear with identical module and helix angle.

The flat plane of D-bore keeps perpendicular to the tooth reference to avoid unbalanced meshing load.

Minimum hub wall thickness: ≥1.5mm for metal gears, ≥2.5mm for plastic gears to prevent torsion cracking.

Our China factory as a reliable manufacturer and supplier implements full dimensional inspection for every batch to meet international transmission assembly standards.

Powder Metallurgy, Metal Injection Molding, Powder Metallurgy Gears

Guangming Group focuses on the R&D and manufacturing of metal forming technology and wear-resistant materials. Its main products cover powder metallurgy parts made by metal compression molding and metal injection molding processes

The company boasts a high-quality talent team. Its founding team originates from Guangzhou Research Institute of Non-ferrous Metals, a research institute directly affiliated with national ministries, owning rich industry experience and strong R&D capabilities that deliver sustainable innovative momentum for the company’s development.

The company has successively obtained5 invention patents and more than 30 utility model patents. It has passed multiple system certifications including IATF16949 Quality Management System, ISO9001-2015 Quality Management System, ISO14001 Environmental Management System and Intellectual Property Management System, and obtained international trademark certification.

It is recognized as an Innovative Enterprise of Guangdong Province, a Guangzhou Science and Technology Little Giant Enterprise, a director unit of the Guangdong Powder Metallurgy Industry Technology Innovation Alliance, and a initiating unit of the Guangzhou Advanced Powder Metallurgy Cluster Promotion Center.