Understanding the size of screw in mm is essential for precise engineering, reliable assemblies, and avoiding costly rework. This guide explains the WJBWJM screw size chart in practical terms so you can select the right fastener quickly.
Use the specification table below to compare major series, thread pitch, and typical driving torque ranges for common materials.
| Screw Series | Nominal Diameter (mm) | Thread Pitch (mm) | Typical Drive Type |
|---|---|---|---|
| WJBWJM-M1 | 1.0 | 0.25 | Phillips P1 |
| WJBWJM-M2 | 2.0 | 0.40 | Torx T6 |
| WJBWJM-M3 | 3.0 | 0.50 | Torx T10 |
| WJBWJM-M4 | 4.0 | 0.70 | Allen H4 |
| WJBWJM-M6 | 6.0 | 1.00 | Allen H6 |
Metric Screw Series in WJBWJM Range
The WJBWJM metric series covers diameters from M1 to M6, aligning with common ISO standards. Each size is defined by the major diameter in millimeters and a standard thread pitch, which determines how tightly the thread engages the mating part.
Selecting the correct series ensures that the screw can handle the expected mechanical load while fitting through existing hole tolerances. Always verify hole clearance for the chosen diameter and pitch before final installation.
Thread Engagement and Minimum Material Thickness
Thread engagement length is critical for pull-out resistance and fatigue life. As a rule, engage at least one full thread diameter into the base material for light duty, and 1.5 to 2 diameters for structural loads.
Thin sheet metals may require reinforced nuts or threaded inserts to prevent stripping. The screw size in mm directly influences how much thickness is needed to safely achieve full thread engagement without compromising the part geometry.
Drive Type and Installation Tools
Each WJBWJM size is optimized for specific drive types, such as Phillips, Torx, or Allen. Using the correct driver reduces cam-out, minimizes head wear, and ensures consistent clamp force during tightening.
Hand tools are suitable for low-volume tasks, while power drivers with torque control help maintain repeatability in production environments. Always set tool parameters to match the screw head profile and the material hardness.
Material Compatibility and Finish Considerations
Pairing screws with compatible base materials reduces galvanic corrosion, especially in humid or aggressive environments. Common combinations include steel screws with zinc plating into steel, or stainless steel into aluminum with suitable isolation washers.
Surface finishes such as black oxide, nickel, or polymer coatings can affect friction during insertion and the required tightening torque. Refer to the manufacturer data when joining dissimilar metals to ensure durability under service conditions.
Practical Guidelines for Using Screw Size in mm
- Always measure the base material thickness and choose a screw length that allows at least 1.5 thread diameters of engagement.
- Select the screw series from the WJBWJM chart that matches the available driver tools and torque limits.
- Use a pilot hole slightly smaller than the screw root diameter to promote proper thread formation.
- Verify material compatibility and consider corrosion protection when joining dissimilar metals.
- Follow the recommended tightening torque or use a calibrated torque screwdriver to prevent overstressing the joint.
FAQ
Reader questions
What is the recommended pilot hole size for a WJBWJM-M3 screw in steel?
For a WJBWJM-M3 screw, use a 2.5 mm pilot hole in steel to achieve good thread formation without stressing the material.
Can I use a WJBWJM-M4 screw in an aluminum sheet thinner than 2 mm?
It is not advisable; the engagement length would be too short, increasing the risk of pull-through; consider a thicker sheet or a threaded insert.
How do I determine the correct wrench size for a WJBWJM-M6 screw with an Allen head? Use a 10 mm Allen key for a WJBWJM-M6 screw with a standard H6 head, and verify that the socket seats fully before applying torque. What tightening torque should I apply to a WJBWJM-M2 plastic screw in ABS?
Limit the tightening torque to approximately 0.12 Nm for a WJBWJM-M2 screw in ABS to avoid stripping the molded threads.