Pre-Assembled Screw and Internal-Tooth Washer
The internal-tooth washer is installed and retained on the screw during production, eliminating the need to prepare or install the washer separately during assembly. This helps reduce assembly steps and improve operating efficiency.
Internal Teeth Provide Auxiliary Anti-Loosening Performance
After tightening, the internal teeth of the washer deform elastically and engage with the underside of the screw head and the mating surface of the workpiece. This increases frictional resistance at the contact area and helps reduce rotational loosening under general vibration conditions.
Actual anti-loosening performance should still be evaluated according to tightening torque, workpiece material, surface hardness, and vibration level.
Suitable for Applications with Limited Outside-Diameter Space
Because the teeth are concentrated around the center hole, the outer edge of an internal-tooth washer is generally smoother than that of an external-tooth washer. This makes it suitable for installation locations with limited surrounding space or where the teeth should not extend beyond the screw head.
Helps Penetrate Surface Oxide Layers or Coatings
When tightened, the internal teeth can bite into the mating surface. Under certain metal assembly conditions, this may help penetrate thin oxide films or surface coatings and improve the stability of metal-to-metal contact.
For products with grounding, electrical conductivity, or electromagnetic compatibility requirements, actual testing should still be performed to confirm contact resistance and electrical continuity.
Reduces the Risk of Missing or Dropped Washers
Because the washer is retained on the screw, it helps reduce missing washers, dropped parts, specification mix-ups, or incorrect assembly order during manual assembly, supporting greater consistency in high-volume production.
Improves High-Volume Assembly Efficiency
Operators only need to handle one complete fastener assembly, eliminating the need to separately pick up the screw and washer. This makes W/INT.WAS. suitable for mass production, rapid assembly, and production lines with demanding cycle-time requirements.
Suitable for Automated Feeding and Fastening
The pre-assembled structure helps reduce problems such as loose washers overlapping, jamming, or becoming incorrectly oriented in vibratory bowls, feeding tracks, or automatic fastening equipment, making it advantageous for automated assembly processes.
Actual automatic feeding performance should still be tested according to the screw head type, screw length, washer outside diameter, and equipment settings.
Simplifies Part Number and Inventory Management
Integrating the screw and internal-tooth washer into a single part number can reduce the number of items that need to be managed during purchasing, inventory control, material issuing, and production-line preparation, while lowering the risk of shortages or incorrect component matching.
Multiple Specifications Available
Different screw head types, drive styles, thread specifications, lengths, and internal-tooth washer dimensions can be selected according to assembly tools, installation space, workpiece material, and fastening requirements.
Customization Based on Drawings and Samples
W/INT.WAS. products can be customized according to customer engineering drawings or physical samples, including screw head type, drive type, thread diameter, thread pitch, length, washer inner and outside diameters, number and profile of teeth, materials, tolerances, and surface treatments.
Common Applications
W/INT.WAS. is commonly used in:
- Electronic and electrical equipment
- Electrical panels, control boxes, and cabinets
- Telecommunications and information equipment
- Machinery and automation equipment
- Automotive and motorcycle components
- Home appliances and consumer products
- Instruments and precision equipment
- Sheet metal and metal enclosures
- Assembly locations requiring auxiliary anti-loosening or metal-to-metal contact
- Mass-production and automated fastening lines
Key Considerations When Selecting W/INT.WAS.
Before selection, confirm the screw thread diameter, thread pitch, length, head type, and drive type. The inner diameter, outside diameter, number of teeth, and thickness of the internal-tooth washer should also be checked against the available installation space.
The internal teeth must sufficiently engage the mating surface to generate the intended frictional resistance. If the workpiece is too hard, the surface coating is too thick, or the washer teeth cannot deform properly, both anti-loosening and contact performance may be affected.
Internal-tooth washers may leave tooth marks on the workpiece surface or scratch paint, plating, or other surface finishes. If the product requires a high-quality appearance, sealing performance, or corrosion protection, the effect of the teeth on the contact surface should be evaluated in advance.
Internal-tooth washers are an auxiliary anti-loosening feature. For applications involving severe vibration, repeated impact, or safety-critical equipment, they should not be relied upon as the sole locking method. Thread-locking compounds, lock nuts, or other mechanical locking methods should also be evaluated.
After repeated assembly and disassembly, the teeth should be inspected for flattening, wear, breakage, or loss of elasticity. If the teeth can no longer effectively engage the mating surface, replacement with a new component is recommended.
