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Stripped threads, corroded fittings, and dust-clogged bores cost time and money. Whether you're capping hydraulic fittings on a job site, protecting valve stems in storage, or masking threads before powder coating, finding the right-sized cap shouldn't be a scavenger hunt. These rubber thread protector caps cover over 100 inner diameters — from tiny Φ1.3mm screws to Φ114mm industrial flanges — so you can stop improvising and start protecting.
Made from a tough vinyl rubber compound, each cap features a smooth, shiny inner surface that slides on without damaging threads. Available in Black and Red, with inner diameters ranging from 1.3mm to 114mm (approximately 0.05" to 4.49"). Packing quantities vary by size: small sizes come in 10pcs, mid-range in 5pcs, larger sizes in 2pcs, and the biggest in 1pc per pack.
Use them on hydraulic pipe joints, oil cylinder ports, threaded rods, flange studs, valve stems, tube ends, and furniture feet. Red caps double as high-visibility safety markers on critical or pressurized lines — a simple color-coding system that saves mistakes on busy shop floors.
Cap open fittings, cylinder ports, and valve stems during maintenance or storage to prevent contamination and corrosion — critical in high-pressure systems where even small debris causes failures.
Protect threaded rod ends, flange studs, and pipe threads from weld spatter, grinding debris, and rust during fabrication — then remove cleanly before assembly.
Mask threads before powder coating or spray painting. These caps withstand typical oven curing up to ~80°C (176°F), keeping threads clean and paint-free without tape or plugs.
Protect threaded components during storage and shipping. Reduce returns and warranty claims caused by thread damage or corrosion in transit — especially for slow-moving inventory.
| Material | Vinyl rubber compound (PVC-based) |
|---|---|
| Available Colors | Black, Red |
| Inner Diameter Range | Φ1.3mm – Φ114mm (approx. 0.05" – 4.49") |
| Small Sizes (10pcs/pack) | Φ1.3mm to Φ25mm |
| Mid Sizes (5pcs/pack) | Φ26mm to Φ40mm |
| Large Sizes (2pcs/pack) | Φ41mm to Φ62mm |
| XL Sizes (1pc/pack) | Φ64mm to Φ114mm |
| Temperature Range | Typically -20°C to +80°C (-4°F to 176°F) |
| Surface Finish | Smooth, shiny inner surface |
| Chemical Resistance | Petroleum oils, hydraulic fluid, water, dust, mild acids |
| Thread Type Compatibility | Straight (parallel) threads and smooth tubing; generally suitable for metric hardware |
| Packing Quantity | See variant options |
Measure the outer diameter of the thread or tube you want to cap. For a snug fit on external threads (bolts, studs), choose a cap with an ID equal to or slightly smaller than the thread's major diameter — rubber will stretch to grip. For smooth pipe ends, match the cap ID to the pipe OD or go 0.5mm under. When in doubt, order one size up and one size down to test fit before buying in bulk.
Yes. The vinyl rubber compound is formulated to resist petroleum-based hydraulic oils, diesel, water, and dust. It also holds up against mild acids and general shop chemicals. For continuous immersion in aggressive solvents such as acetone or concentrated acids, we recommend testing a sample first or considering a specialty material like Viton.
Yes — this is one of the most common uses. These caps withstand typical powder coat oven curing temperatures up to approximately 80°C (176°F). For higher-temperature baking above 100°C (212°F), silicone caps are recommended. For standard spray painting at room temperature, these work perfectly and remove cleanly without leaving residue.
These caps are designed primarily for straight (parallel) threads and smooth tubing. On NPT tapered fittings, the cap will cover the threads but may not seat tightly at the base due to the taper. For a secure seal on NPT fittings, contact us — we can recommend tapered thread protector options.
Typical operating range is generally -20°C to +80°C (-4°F to 176°F). They soften at higher temperatures and may become brittle below -20°C. For extreme cold environments or high-heat applications such as engine compartments, silicone or high-temp rubber alternatives are available — contact us for guidance.
This listing currently includes black and red only. For large-volume orders, custom colors such as blue, yellow, green, white, or clear may be available on request. Minimum order quantities typically apply. Contact customer service to discuss custom color options for your project.
Packing quantity is based on the physical size of the cap. Smaller caps (Φ1.3mm–Φ25mm) are compact and typically used in higher quantities, so they come in 10pcs per pack. Mid-range sizes (Φ26mm–Φ40mm) come in 5pcs. Larger caps (Φ41mm–Φ62mm) come in 2pcs, and the largest sizes (Φ64mm–Φ114mm) come individually (1pc) due to their size and typical usage patterns.
