Knurl Pattern Importance
The exterior surface of a knurled insert nut affects its performance more than the internal thread. Knurls-raised ridges cut or rolled into the OD-displace host material during installation and resist rotational torque and axial pull-out after cooling or curing.
Three common knurl profiles are machined:
- The straight knurl is ideal for controlled press-fit and heat-set applications that prioritise linear pull-out resistance.
- Diagonal knurl: A spiral grip that prevents rotation in both directions, commonly used in consumer electronics.
- The diamond knurl is the preferred option for high-vibration assemblies because to its combination of axial and torsional resistance.
We use CNC-controlled turning centres to maintain knurl depth, pitch, and OD tolerance within ±0.02 mm. Custom Brass Knurled Insert Nuts are consistent, unlike off-the-shelf inserts that loosen during temperature cycling.
Alternative Materials to Brass
The standard Brass Knurled Insert Nut is made from Brass C3604, which machines cleanly, conducts heat quickly during ultrasonic or heat-set installation, and resists corrosion indoors and in light outdoor uses. Golden is completing work for conspicuous consumer products.
For more extreme situations or engineering requirements we have various materials:
- Corrosion of brass is limited to marine, medical and chemical exposure applications. Stainless steel 303/316.
- Aluminium 6061 for weight sensitive drone and robotics assembly.
- Copper and copper alloys are used to ground and shield electrical devices from EMI.
DFM is validated by checking the thermal expansion, galvanic compatibility and load of the knurled brass insert with the host material.
Installation Methods
This threaded insert can be placed in numerous ways depending on production volume and host material:
The insert is inserted into a pre-molded or drilled hole using a heated tool to soften the surrounding plastic. Plastic hardens in the knurl, providing a mechanical lock. Suitable for ABS, PC, and nylon housings.
Ultrasonic insertion
A 20 kHz horn vibrates the insert, causing melt at the knurl interface. Faster and less damaging to cosmetic surfaces than heat-set. Medical devices and electronics enclosures contain them.
The knurl is encapsulated in molten plastic by inserting it into the injection mould cavity before injection. It resists pull-out and torque best but requires precise mould tooling.
Press-fit insertion works for ductile metals and thermoplastics by pressing the insert into an interference-fit hole. Fits metals where heat would distort features.
We install according to part geometry, surface finish sequence, and production volume.
Engineering Specifications
All dimensions are verified with thread gauges, optical comparators, and CMM inspection before shipment.
Metric threads: M2 to M12 (M3, M4, M5 most common)
Length: 3 mm to 25 mm, custom to drawing
Imperial threads: 2-56 to 1/4-20, UNC/UNF
Knurl pitch: 0.3 mm to 1.0 mm, straight, diagonal, or diamond
Outer diameter: Custom to your hole design, typically 3 mm to 16 mm
Tolerances: Thread pitch diameter ±0.01 mm; OD ±0.02 mm; length ±0.05 mm
Surface treatment: Nickel plating, passivation, tin plating, natural polished brass
Ordering & Lead Time
Send your STEP, IGES, or DWG file plus thread size, material, knurl type, and installation method. We return quotes within 24 hours. Prototype quantities ship in 7–10 days; production volumes in 2–3 weeks. No fixed minimum order quantity.
FAQ
Q: Can a knurled brass insert be used in metal parts?
A: Yes, with press-fit or adhesive-bonded installation. Brass is softer than most host metals, so interference and galvanic compatibility must be reviewed during DFM.
Q: What is the difference between heat-set and ultrasonic installation?
A: Heat-set uses a heated tool to melt plastic around the knurl; ultrasonic uses high-frequency vibration. Ultrasonic is faster and leaves less surface witness mark; heat-set tooling is lower cost.
Q: Do you offer inserts in materials other than brass?
A: Yes. We machine knurled brass inserts as well as stainless steel, aluminum, and copper variants, selecting material based on corrosion, weight, conductivity, and cosmetic requirements.
Q: What drawing format do you need for a quote?
A: STEP, IGES, or DWG files are preferred. Include thread specification, knurl type, material grade, quantity, and installation method.
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