Guangming Group will talk about D-hole spur gears today

D-hole spur gear=spur cylindrical gear+D-hole, specially designed for trimming D-axis motors/shafts, no key, no top thread, anti slip, quick assembly and disassembly, it is the mainstream gear for small transmission (automation/robot/DIY).

1、 Core structure (easy to understand at a glance)

Tooth profile: standard straight teeth (cylindrical straight teeth), pressure angle of 20 °, smooth meshing, no axial force.

Inner hole: D-shaped hole (round hole+flat edge cutting), matched with motor D-axis, fixed in the circumferential direction without slipping.

Material:

Plastic: POM/nylon (low noise, wear-resistant, low-cost, lightweight);

Metal: brass/45 steel/stainless steel (high-strength, temperature resistant, medium to heavy load).

Modulus: commonly used M0.5/M0.8/M1.0/M1.5 (small), M2/M3 (industrial).

Number of teeth: 10-50 teeth; Aperture: D3/D4/D5/D6/D8mm (matched with N20/370/540 motors).

2、 Working principle (why doesn't it slip)

Ordinary circular hole: fixed by top thread/glue, easy to loosen and slip due to vibration;

D-shaped hole: The inner hole plane is tightly adhered to the D-axis plane, locked in the circumferential direction, and torque is directly transmitted without slip or backlash;

Installation: Directly push in, no keyway/top thread required, 1 second installation and removal.

3、 Key parameters (mainstream in 2026)

table

Typical parameter values description

Modulus M 0.5/1.0/1.5 tooth size, M0.5 is most commonly used (N20 motor)

Number of teeth Z 12-20 teeth 15 teeth is the most common (outer diameter ≈ 8.5mm, M0.5)

D-hole size 3/4/5/6mm matching motor shaft diameter (e.g. N20=3mm D-axis)

Pressure angle of 20 ° standard value, smooth meshing

Material POM/brass/steel POM low noise; Steel impact resistance

Torque 0.1-2Nm plastic ≤ 0.5Nm; metal ≥ 1Nm

4、 Core advantages (compared to circular holes/keyways)

✅  Anti slip: D-shaped fit, zero slip, no loss of rotation under vibration/load;

✅  Tool free: Push in and install, no need for threading/keys/glue, quick changeover;

✅  Low backlash: no backlash in the circumferential direction, accurate positioning, fast response (robot/precision transmission);

✅  Low cost: Keyless machining, with a price reduction of over 30%, suitable for bulk production;

✅  Low noise and stable: Straight teeth+POM material, low noise and minimal vibration.

5、 Typical applications (related to your device)

Small motor: N20/370/540 reduction motor (micro drive for filling/labeling machines);

Automation equipment: Star wheel labeling machine, sealing machine, small torque transmission of pump body;

Robot: joint/walking wheel drive, anti slip, accurate positioning;

Model/DIY: Model airplane/car/robotic arm, low-cost and easy to assemble.

6、 Common faults+solutions

Slipping/spinning: D-hole wear → replace metal gear; Axis deformation → straightening or shaft replacement;

Unable to install/too tight: D hole tolerance is small → slight hole enlargement (POM) or change to compatible model;

High noise: rough tooth surface → replace with precision molded/metal gears; Lack of oil → add silicon-based grease;

Broken teeth: excessive load → replace metal material; Poor meshing → calibrate center distance.

7、 Selection points (avoiding pitfalls)

D-hole size: must match the motor D-axis (e.g. N20=3mm D-hole);

Modulus/number of teeth: Select according to speed ratio/torque, M0.5 is commonly used (small);

Material: Choose POM for light load and low noise; Medium to heavy load/impact steel/brass selection;

Torque: Plastic ≤ 0.5Nm; Metal ≥ 1Nm, leaving 20% redundancy;

Precision: Precision transmission for metal precision milling; POM injection molding is selected for ordinary transmission.

8、 Difference from D-hole helical gears

Straight teeth: no axial force, low noise, easy to machine, high speed ≤ 1000rpm, light load;

Diagonal teeth: smooth meshing, high torque, axial force, high-speed ≥ 1500rpm, heavy load.

Powder metallurgy, metal injection molding, powder metallurgy gears

Guangming Group focuses on the research and development of metal forming technology and wear-resistant materials. Its main products include metal compression molding and injection molding powder metallurgy products.

The company has a team of high-quality talents, with the founding team originating from the Guangzhou Nonferrous Metals Research Institute, a directly affiliated national and ministerial level scientific research institution. It has rich industry experience and research and development capabilities, providing a continuous source of innovation power for the company's development. The company has successively obtained 5 invention patents and more than 30 utility model patents. It has passed the IATF16949 quality management system, ISO9001-2015 quality management system, ISO14001 environmental management system, intellectual property management system, and obtained international trademark certification. It is an innovative enterprise in Guangdong Province, a small giant enterprise in science and technology in Guangzhou, a member of the Guangdong Powder Metallurgy Industry Technology Innovation Alliance, and an initiator of the Guangzhou Advanced Powder Metallurgy Cluster Promotion Center.