Product Overview
Reliable custom rubber parts for industrial applications
Quick Answer
High-temperature silicone round end caps are dome-shaped protective sleeves for thread masking, shaft-end protection and metal finishing processes. They are used in powder coating, painting, anodizing, electroplating and packaging protection. Inner diameter, length, wall thickness, silicone compound, hardness, color, tolerance and packaging can be customized.
High-temperature silicone round end caps are translucent dome-shaped protective sleeves used for thread protection, shaft-end covering and surface-treatment masking. The closed-end and open-mouth design allows direct installation over bolts, threaded fittings, shafts or tube ends. Inner diameter, length, wall thickness, hardness, color and packaging can be customized according to drawings, samples or application requirements.
High-Temperature Silicone Round End Caps — Dome-Shaped Masking and Thread Protection Caps
High-temperature silicone round end caps are dome-shaped, one end closed protective caps molded from high-purity VMQ silicone, designed to slide directly over cylindrical metal rods, bolts, connectors, or shaft ends. Built for industrial surface treatment and parts protection, these caps combine a clean transparent silicone finish with the heat resistance needed for coating and finishing processes.
Key Specifications
| Parameter | Specification |
|---|---|
| Product Name | Tuelle_Silikonkappe (silicone grommet/cap) |
| Material | Silicone (VMQ) |
| Hardness | 50 Shore A |
| Color | Transparent |
| Weight/Volume | 2.3 g |
| Outer Diameter | Ø14 mm |
| Inner Diameter | Ø11.7 mm (+0.40/-0.40 tolerance) |
| Overall Length | 45 mm |
| Radius | R7 (domed tip radius) |
| General Tolerance | DIN ISO 3302-1 M3 |
| Mold Separation Offset | +/- 0.15 mm |
| Height/Width Tolerance | Height: 0.1 mm, Width: 0.3 mm |
| Drawing Reference | WZG-NR 1043, Rev. A, Scale 1:1, Size A4 |
| Manufacturer | Julong Rubber |
Primary Applications
High-Temperature Masking Caps for Surface Treatment
This is the most common use for this cap style. During powder coating, anodizing, plating, or electrophoretic (e-coating) processes on metal parts, the cap is fitted over precision sealing surfaces or threaded sections that must remain free of coating.
- Blocks paint, powder, or chemical treatment fluid from entering the threaded area.
- Ensures the thread remains fully functional and easy to fasten after the coating cycle.
- Silicone’s natural non-stick property allows cured paint or coating residue to peel away easily after the process.
Shaft End and Precision Thread Protection
The same cap design is also used to protect finished metal parts during storage, transport, and general handling.
- The silicone’s cushioning properties help prevent impact damage or scratching to precision external threads, splined shafts, or polished tube ends.
- The tight fit also blocks moisture and salt spray from reaching the mating surface, reducing the risk of corrosion at the connection point during storage or shipping.
Technical Advantages of Silicone Material
Outstanding High-Temperature Performance
The VMQ silicone compound withstands the 200°C to 250°C range commonly encountered in powder coating bake ovens and similar high-temperature processes, without melting, hardening, or releasing contaminating fumes during extended bake cycles.
Excellent Elasticity and Interference Fit
Silicone offers very high elongation, which allows the cap to stretch snugly over a workpiece. Based on the reference drawing, the standard bore of Ø11.7 mm is designed to grip a slightly larger metal diameter through elastic tension; in general selection practice, an inner diameter about 0.5mm to 1mm smaller than the metal outer diameter is chosen so the cap grips the thread tightly, preventing it from slipping off or leaking during spray or wash-down steps.
Reusability
The material resists tearing and abrasion, allowing the caps to be cleaned of paint residue and reused across multiple production cycles, which significantly reduces the overall masking cost per part compared with single-use alternatives.
Sizing and Fit Guide
Selecting the correct cap starts with matching the cap’s inner diameter to the outer diameter of the rod, bolt, or shaft being protected, generally choosing an ID about 0.5mm to 1mm smaller than the workpiece OD to achieve a secure interference fit. Cap length should be selected based on how much of the exposed thread or shaft section needs to be covered, with longer caps used for extended threaded studs and shorter caps for compact bolt heads or connector ends. A properly fitted cap should stay firmly in place through spray, dip, or wash-down steps without slipping or allowing coating material to seep underneath the open edge.
Common Applications
- Powder coating line masking for threaded fasteners and precision bores.
- Anodizing and electroplating masking for aluminum and metal components.
- Electrophoretic (e-coating) paint line thread protection.
- Shipping and storage protection for polished shafts, splined rods, and threaded connectors.
- General metal parts handling protection against corrosion and impact damage.
Custom Manufacturing Options
- Custom length, inner diameter, and wall thickness beyond the standard Ø14 x 45mm reference.
- Custom silicone hardness (Shore A) for different fit tightness requirements.
- Custom color for process identification (e.g., differentiating cap sizes by tint).
- High-temperature grade selection based on specific bake oven or process temperature.
- OEM branding and private-label packaging.
FAQ
What are high-temperature silicone round end caps used for?
High-temperature silicone round end caps are used for masking threads, fittings, shaft ends, tube ends and sealing surfaces during powder coating, painting, anodizing, electroplating and other surface-treatment processes. They are also used for thread protection and material protection during packaging, storage and transport.
Can the cap dimensions be customized?
Yes. Inner diameter, outer diameter, length, wall thickness, dome profile and tolerance can be customized according to drawings, size lists or physical samples. Unsupported dimensions should not be assumed because grip force, masking coverage and installation fit depend on confirmed size data.
How should buyers choose the correct inner diameter?
The inner diameter should be selected according to the outside diameter of the thread, shaft, connector or tube being protected. For many applications, a slight interference fit can improve holding force. The final selection should consider installation force, removal method, temperature and process conditions.
Are these silicone caps suitable for powder coating masking?
They can be used for powder coating masking when the silicone compound, size and temperature resistance match the curing process. Buyers should provide oven temperature, exposure time, coating thickness, part geometry and reuse requirements before confirming the most suitable cap specification.
Can the caps be reused?
Reuse may be possible when the silicone cap is not torn, excessively contaminated, hardened or deformed after processing. Reuse performance depends on temperature, coating residue, chemical exposure, cleaning method and handling condition. Buyers should test samples under actual production-line conditions.
Are samples available before bulk production?
Samples are available upon request. Sample preparation depends on cap size, silicone compound, hardness, color, tooling status and inspection requirements. A metal part sample, drawing or size list helps confirm ID, length, grip force and masking coverage before batch production.
Request a Custom Quote
Send your high-temperature silicone round end cap drawing, metal part drawing, size list or physical sample for review. Please include ID, length, wall thickness, material requirement, hardness, working temperature, surface-treatment process, protected area length, quantity, annual demand and packaging requirements.
