Fir Tree studs are fasteners with a serrated geometry that allows components to be push-fitted onto sheet metal without threads or nuts.
Fir Tree studs for short-cycle welding feature conical fins or teeth that create a push-fit in holes or soft materials, eliminating the need for additional threads or nuts.
Made of copper-plated grade 4.8 steel or A2-50 stainless steel, with a 5 mm shank (d1) and lengths of 9, 14.2, 18 and 25 mm.
Fir Tree studs for short-cycle welding are ideal for fastening plastic components, fibre panels, insulation or clips in the automotive, domestic-appliance and HVAC industries.
1. What are Fir Tree studs?
Fir Tree studs take their name from their distinctive geometry: a series of progressively widening conical fins or teeth resembling the branches of a fir tree. This design allows the stud to be push-fitted into holes or soft materials without additional tools.
They are widely used where plastic components, fibre panels, wiring harnesses or insulation must be secured to sheet metal onto which the Fir Tree stud has previously been welded.
2. Technical specifications
Available materials
| Material | Tensile strength (Rm) | Yield strength (Re) | Elongation |
|---|---|---|---|
| Grade 4.8 steel (copper-plated) | ≥ 420 N/mm² | ≥ 340 N/mm² | ≥ 14% |
| A2-50 stainless steel | ≥ 500 N/mm² | ≥ 210 N/mm² (Rp0.2) | ≥ 0.6 d |
Fir Tree geometry
- Shank: Diameter d1 = 5 mm
- Conical fins: Allow push-fit insertion and resist pull-out
- Flange: Diameter d2 = 6.5 mm ±0.2, with height h1 = 0.7–1.4 mm
- Surface protection: 4–8 μm electrolytic copper coating (grade 4.8 steel)
3. Dimension table – Fir Tree studs
| d1 (mm) | l1 (mm) +0.6 | d2 (mm) ±0.2 | h1 (mm) | Grade 4.8 steel item no. | A2-50 item no. |
|---|---|---|---|---|---|
| 5 | 9 | 6.5 | 0.7-1.4 | 07-05-009 | 08-05-009 |
| 5 | 14.2 | 6.5 | 0.7-1.4 | 07-05-014.2 | 08-05-014.2 |
| 5 | 18 | 6.5 | 0.7-1.4 | 07-05-018 | 08-05-018 |
| 5 | 25 | 6.5 | 0.7-1.4 | 07-05-025 | 08-05-025 |
Note: l2 (length after welding) depends on l1 and the welding energy. Other lengths and materials (1.4571) are available on request.
4. Welding-gun compatibility
Fir Tree studs are compatible with PHM-10, GD 12sc and PHM-1A welding guns, using the following chucks according to diameter:
| Diameter (d1) | l2 (projected length) | Chuck / nut (item no.) |
|---|---|---|
| 5 mm | l2 ≤ 40 | 82-50-005 |
| 5 mm | l2 > 40 | 82-50-005 with intermediate ring |
5. Typical applications
- Automotive industry: Fastening fibre panels, mats and interior trim
- Domestic appliances: Securing acoustic and thermal insulation in washing machines and refrigerators
- HVAC: Installing ventilation ducts and insulation panels
- Wiring harnesses: Anchoring points for cable clamps
- Plastics and composites: Quick fastening without threads or nuts
6. Advantages of the Fir Tree system
- Quick installation: Simply press the component onto the stud, with no tools required
- No nuts or threads: Reduces the cost of additional components
- Vibration resistance: The fins prevent loosening through vibration
- Removable: Components can be removed with a controlled pull
- Versatility: Compatible with plastics, fibres and composite materials
7. Practical recommendations
- Select the l1 length according to the thickness of the component to be fastened
- For very soft materials, use the longest version (25 mm) for better anchoring
- Check that the hole in the component has the correct diameter for the Fir Tree stud
- For corrosive environments, choose A2-50 stainless steel
- Carry out pull-out tests to validate the holding force
8. Comparison between Fir Tree and other systems
| System | Installation | Tools | Removal | Cost |
|---|---|---|---|---|
| Fir Tree | Manual push-fit | None | Possible | Low |
| Threaded stud + nut | Screwed | Spanner or screwdriver | Easy | Medium |
| Spring clip | Push-fit | Pliers (for removal) | Possible | Low |