Cap Nuts
422 ProductsCap Nuts
Plastic Cap Nuts
Plastic cap nuts are lightweight, corrosion-resistant fasteners that provide a protective cover for exposed threads, offering insulation, resistance to rust and chemicals, and an economical solution for applications in electronics, construction, and outdoor environments where moderate strength is required.
Sanitary Thread Caps
Sanitary thread caps are designed to cover and protect exposed threads, preventing the accumulation of dirt, debris, and contaminants in hygiene-critical environments such as food processing, pharmaceuticals, and cleanrooms, ensuring easy cleaning and maintaining sanitary conditions.
High-Profile Cap Nuts
High-profile cap nuts feature an extended dome-shaped design that offers increased protection for longer exposed threads, providing enhanced durability and security in applications where extra thread coverage and a strong fastening solution are needed.
Low-Profile Cap Nuts
Low-profile cap nuts feature a compact, dome-shaped design that sits flush with the surface, providing a sleek and space-saving solution while protecting exposed threads, ideal for applications where minimal protrusion and a clean finish are required.
Stainless Steel Extra-Wide High-Hex Cap Nuts
Stainless steel extra-wide high-hex cap nuts combine a wide hexagonal design for increased torque and a high-profile cap that protects exposed threads, providing excellent corrosion resistance and durability for heavy-duty applications in harsh or corrosive environments.
Steel Extra-Wide High-Hex Cap Nuts
Steel extra-wide high-hex cap nuts feature an enlarged hexagonal design for increased torque application and a high-profile cap that provides added protection for exposed threads, offering a strong and durable fastening solution for heavy-duty applications requiring high strength and secure connections.
Sanitary Low-Profile Cap Nuts
Sanitary low-profile cap nuts feature a smooth, low-profile design that prevents the accumulation of contaminants, providing a hygienic, easy-to-clean fastening solution ideal for applications in food processing, pharmaceuticals, and clean environments.
Aluminum Cap Nuts
Aluminum cap nuts are lightweight, corrosion-resistant, non-magnetic, conductive, aesthetically appealing, cost-effective, recyclable, easy to install, durable, thread-protective, and non-sparking, making them ideal for a wide range of applications in industries requiring moderate strength and environmental resistance.
Brass Cap Nuts
Brass cap nuts offer excellent corrosion resistance, electrical conductivity, and a visually appealing finish, with a protective dome-shaped design to cover exposed threads, making them ideal for decorative, electrical, and moderate-strength applications.
Metric Plastic Cap Nuts
Metric plastic cap nuts provide a lightweight, non-corrosive fastening solution in metric sizes, with a protective dome-shaped design to cover exposed threads, ideal for applications requiring moderate strength, insulation, and resistance to rust or chemicals.
18-8 Stainless Steel Cap Nuts
18-8 stainless steel cap nuts offer excellent corrosion resistance with a dome-shaped design to protect exposed threads, providing durable and secure fastening solutions for both indoor and outdoor applications where moderate strength and long-term resistance to rust are required.
Medium-Strength Steel Cap Nuts
Medium-strength steel cap nuts provide a balance of durability and load-bearing capacity with a protective dome-shaped design, offering secure fastening for applications requiring moderate strength and protection for exposed bolt threads.
Metric High-Strength Steel Cap Nuts—Class 10
Metric high-strength steel cap nuts—Class 10 provide superior strength and load-bearing capacity in metric sizes, offering a secure, protective fastening solution for high-stress applications in demanding environments.
High-Strength Steel Cap Nuts—Grade 8
High-strength steel cap nuts—Grade 8 offer exceptional durability and load-bearing capacity, with a dome-shaped design to protect exposed threads, making them ideal for high-stress applications requiring secure and reliable fastening in demanding environments.
Metric Low-Strength Steel Cap Nuts
Metric low-strength steel cap nuts provide a protective dome-shaped design for exposed bolt threads in metric sizes, offering a cost-effective solution for applications with moderate loads and basic corrosion resistance in less demanding environments.
Low-Strength Steel Cap Nuts
Low-strength steel cap nuts feature a dome-shaped design that protects exposed bolt threads while offering a cost-effective solution for applications with moderate load requirements, providing basic corrosion resistance and secure fastening in non-demanding environments.
Metric Super-Corrosion-Resistant316 Stainless Steel Cap Nuts
Metric super-corrosion-resistant 316 stainless steel cap nuts provide outstanding corrosion resistance in metric sizes, particularly in marine and harsh environments, with a closed-end design that protects exposed threads, ensuring secure and long-lasting fastening in highly corrosive conditions.
Super-Corrosion-Resistant 316 Stainless Steel Cap Nuts
Super-corrosion-resistant 316 stainless steel cap nuts offer exceptional resistance to corrosion, especially in harsh or marine environments, with a closed-end design that protects exposed threads, providing secure and durable fastening for long-term applications in highly corrosive conditions.
Metric 18-8 Stainless Steel Cap Nuts
Metric 18-8 stainless steel cap nuts feature a closed-end design that protects exposed bolt threads while providing excellent corrosion resistance, making them ideal for secure, aesthetically pleasing threaded connections in metric sizes for both indoor and outdoor applications.
Cap Locknuts
Metric Nylon-Insert Cap Locknuts
Metric nylon-insert cap locknuts feature a nylon insert that provides a secure, vibration-resistant locking mechanism, preventing loosening while offering durable, reusable threaded connections in metric sizes, ideal for precision applications in dynamic environments.
18-8 Stainless Steel Distorted-Thread Cap Locknuts
18-8 stainless steel distorted-thread cap locknuts feature a deformed thread that provides a secure, vibration-resistant locking mechanism, combined with the corrosion resistance of 18-8 stainless steel, making them ideal for durable fastening in challenging environments where resistance to loosening and corrosion is required.
Nylon-Insert Cap Locknuts
Nylon-insert cap locknuts feature an integrated nylon insert that provides a secure, vibration-resistant locking mechanism, preventing loosening while offering protection for the bolt threads, making them ideal for applications where a secure, reusable fastening is needed.
Metric 18-8 Stainless SteelVibration-Resistant Cap Locknuts
Metric 18-8 stainless steel vibration-resistant cap locknuts offer corrosion resistance with a secure locking mechanism designed to prevent loosening under vibration, providing durable, reliable threaded connections in metric sizes for applications in moderately corrosive and dynamic environments.
18-8 Stainless Steel Vibration-Resistant Cap Locknuts
18-8 stainless steel vibration-resistant cap locknuts feature a durable, corrosion-resistant construction with a locking mechanism to prevent loosening under vibration, making them ideal for securing threaded connections in environments exposed to movement or moderate corrosion.
Low-Strength Steel Distorted-Thread Cap Locknuts
Low-strength steel distorted-thread cap locknuts feature a distorted thread for secure locking under vibration and moderate loads, providing a cost-effective solution for applications requiring reliable fastening in less demanding environments.
Super-Corrosion-Resistant 316 StainlessSteel Vibration-Resistant Cap Locknuts
Super-corrosion-resistant 316 stainless steel vibration-resistant cap locknuts feature a secure locking mechanism to prevent loosening under vibration and are made from 316 stainless steel, providing excellent corrosion resistance in harsh environments.
Super-Corrosion-Resistant 316 StainlessSteel Distorted-Thread Cap Locknuts
Super-corrosion-resistant 316 stainless steel distorted-thread cap locknuts feature a distorted thread for vibration resistance and are made from 316 stainless steel, offering exceptional corrosion resistance and secure locking in harsh environments.
LILY Bearing stocks 422 cap nuts — in Inch (353 SKUs) and Metric (69 SKUs) — across 30 variations covering profile, locking, sealing, and material options. Use the filters below, or the comparison table, to narrow down by cap style, material, or thread size.
Compare Cap Nut Types
| Type | How It Works | Best For | Watch Out For | Materials |
|---|---|---|---|---|
| Standard Cap Nuts | Closed, domed top fully covers the bolt's exposed threads | Exposed threads on visible or safety-sensitive assemblies | Bolt length must not exceed the nut's internal depth | Steel, stainless steel, brass, aluminum, plastic |
| High-Profile Cap Nuts | Extended dome gives more internal clearance than a standard cap | Bolts with longer exposed thread that a standard cap won't clear | Taller profile needs more clearance above the joint | Steel, stainless steel |
| Low-Profile Cap Nuts | Compact dome sits flush or nearly flush with the surface | Tight spaces where a standard-height cap won't fit | Less internal depth to cover longer exposed threads | Steel, stainless steel |
| Open-End Cap Nuts | Dome is open at the top, so the bolt can extend through | Bolts of any length, including ones longer than the nut | Does not fully enclose the thread tip like a closed cap does | 18-8 stainless steel |
| Cap Locknuts | Adds a nylon insert or a distorted (deformed) all-metal thread inside the cap to grip the bolt and resist loosening | Vibration-prone assemblies that also need covered threads | Nylon-insert versions have a lower temperature ceiling (≈250°F) than distorted-thread (all-metal) versions | Steel, 18-8 stainless steel, 316 stainless steel, brass |
| Sealing Cap Nuts | Integrated silicone seal at the base blocks moisture, debris, and contaminants | Sealed connections rated up to 1,200 psi and wide temperature swings | Confirm the seal's pressure and temperature rating against your application | 18-8 stainless steel |
| Sanitary Thread Caps | FDA-compliant cap with a smooth, cleanable surface and a silicone seal | Food processing, pharmaceutical, and cleanroom environments | Confirm your facility's specific hygiene standard is covered | 304 stainless steel |
| Extra-Wide High-Hex Cap Nuts | Enlarged hex flats give a wrench more surface to apply higher torque | Heavy-duty joints needing both high torque and thread protection | Larger hex size needs more surrounding clearance | Steel, stainless steel |
| Cap Nut Assortments | Compartmented kit with multiple common sizes in one container | Maintenance, prototyping, or stocking a range of sizes at once | Fixed size range and piece count per kit — check it covers what you need | 18-8 stainless steel |
Locking, Sealing & Hygiene Options
A standard cap nut protects and finishes exposed threads but has no built-in resistance to loosening. Cap locknuts add that resistance two ways: a nylon insert grips the bolt but is limited to roughly 250°F, while a distorted (deformed) all-metal thread grips harder and holds up in higher-temperature environments. For applications where moisture or pressure is the concern rather than vibration, sealing cap nuts use an integrated silicone seal rated up to 1,200 psi. Sanitary thread caps go a step further for food, pharmaceutical, and cleanroom use — they're FDA-compliant (21 CFR 177.2600) and available in metal-detectable and X-ray-detectable versions to support contamination-control programs.
Need a Custom Cap Nut or a Part Cross-Reference?
Working from an existing McMaster-Carr or manufacturer part number? Our team can cross-reference it to an equivalent LILY Bearing cap nut, or quote a custom material, seal, or finish. Request a Quote or Contact Us.
Frequently Asked Questions
What's the difference between a standard cap nut and a cap locknut?
A standard cap nut only covers and protects the exposed threads — it relies on thread friction alone and has no resistance to loosening. A cap locknut adds a nylon insert or a distorted all-metal thread inside the cap that actively grips the bolt to resist vibration-induced loosening.
What's the difference between high-profile, low-profile, and open-end cap nuts?
High-profile cap nuts have a taller dome for extra clearance over longer exposed threads. Low-profile cap nuts have a shorter, flush-fitting dome for tight spaces. Open-end cap nuts have no closed top at all, so the bolt can pass all the way through — useful when the bolt is longer than any closed cap could cover.
Are your cap nuts food-safe or hygienic-environment rated?
Our Sanitary Thread Caps are FDA-compliant under 21 CFR 177.2600 and available in metal-detectable and X-ray-detectable versions for food processing, pharmaceutical, and cleanroom environments. Standard cap nuts are not rated for these uses.
Do you offer cap nut assortments or kits?
Yes. Our Cap Nut Assortments come in compartmented containers covering a range of common sizes in a single kit, useful for maintenance work or stocking multiple sizes at once.
