Caps, Grips, and Closures Information

Show all Caps, Grips, and Closures Manufacturers

Grips, caps, and closures are used to protect the end of a shaft, tube, pipe, bottle, screw, bar, or other item during shipping, storage, masking, or other applications. Some caps can also be used to provide a hand grip or hanger tip. They are made of plastic, metal, paper or other materials. The most important factor in grip, cap, and closure selection is the type. Type is defined either by the shape of the cap or the means by which the cap is fitted.

Shape Type

Type	Description	Example
Round-shaped	Round or circular shaped caps and plugs have circular dimensions and are meant to fit onto objects with round ends, such as bottles or circular tubes.	Image credit: SKS Science Products
Square-shaped	Square shaped caps and plugs have equal length and width dimensions and are meant to fit onto objects with square ends.	Image credit: MOCAP, Inc.
Rectangular-shaped	Rectangular shaped caps and plugs have varying length and width dimensions and are meant to fit onto objects with rectangular ends.	Image credit: LADD Industries, Inc.
Hand grips	Hand grips are caps used specifically as handles or grips. They may have finger nubs for easier gripping. Round handles have circular cross sections. Flat grips have square or rectangular cross sections.	Image credit: Alliance Plastics
Hex caps	Hex caps are hex-shaped for use with hex stock, nuts, and fittings.	Image credit:MOCAP, Inc.
Screw caps	Screw caps or plugs are specifically designed for covering a screw or screw socket.	Image credit: Direct Industry
Washer caps	Washer caps have holes in the center and are used between tubes or hoses and end fittings.	Image credit: Daemar Inc.

Connection Type

Grips, caps, and closures are designed with one of three connection methods.

Type	Description	Example
Push-fit	Push-fit caps and plugs connect to ends simply by applying downward pressure. These closures typically provide a tight fit, but are easy to remove.	Image credit: Alliance Express
Tapered	Tapered caps and plugs are connectors with tapered sides, providing a snug fit. Some can be used as either a cap or a plug. Tapered caps and plugs are versatile and can be used for straight tubes and bars, male and female NPT threads, and male straight threads.	Image credit: Daemar, Inc.
Threaded	Threaded caps and plugs have threads designed to attach to threaded ends of pipes, tubes, and other forms. Caps have female threads and plugs have male threads. Some threaded caps may incorporate a quick-twist style with a clip or lock that engages the cap in place.	Image credit: Hi-Tech Seals, Inc.

Sizing Specifications

Cap dimensions must be matched and selected according to the object they are covering or protecting. Sizing specifications will vary based on the shape of the cap.

Circular Dimensions

These dimensions only apply to round caps.

Diameter is a dimension expressing the cross sectional distance spanning across the cap circumference. Caps should be sized in order to fit the diameter of the round objects they are capping or covering.
BSP sizing applies to caps designed to fit objects with male BSP (British Standard Pipe) threading.
NPT sizing is used for closures designed to cap objects with male NPT (National Pipe Thread) threads.

Square or Rectangular Dimensions

These dimensions only apply to square or rectangular caps.

Length is the larger cross sectional dimension for rectangular caps. If the section is a square, the width and length are the same dimension.
Width is the smaller cross sectional dimension for rectangular caps. If the section is a square, the width and length are the same dimension.

Material

Metal Caps, Grips, and Closures It is also important to consider the material of the grip, cap, or closure. Material typically dictates the physical properties of the cap; most importantly its hardness, flexibility, and resistance to wear or degradation. Additionally, it is often important for the material to match that of the item being protected or covered.

Metals

Aluminum is a very versatile metal that is lightweight, strong, durable, flexible, impermeable, corrosion-resistant, and recyclable.
Stainless steel is a steel alloy containing over 10.5% chromium. It is used in applications where excellent corrosion resistance and high strength are required.

Plastics

Ethyl vinyl acetate (EVA) is a transparent thermoplastic elastomer. It remains flexible at low temperatures and resists cracking. Brand names include: Ultrathene® (Quantum), Elvax® (DuPont), Evalca® (Eval).
Nylon, comprising several grades of polyamides, is a general purpose material in wide use; it is tough and resistant and has good pressure ratings and mechanical strength for its cost.
Polyethylene (PE) comes in high density (HD) and low density (LD) forms. The high density form is a high strength, rigid plastic with temperature resistance up to 215°F. The low density form is a flexible, semi-rigid plastic with a temperature resistance up to 175°F. Low density polyethylene is the most common material used for manufacturing caps and plugs.
Polypropylene (PP) is a high strength, rigid thermoplastic material exhibiting excellent cold flow, bi-axial strength, and yield elongation properties. It is similar to PVC but can be used in exposed applications because of its resistance to UV, weathering, and ozone. It resists temperatures up to 250°F.
Vinyl exhibits good flexibility and chemical resistance; it is used in many medical and chemical applications. Its properties can be enhanced or modified by compounding it with additives or modifiers to meet different application needs.

Other

Paper caps are considered more environmentally friendly than plastics and metals and are typically 100% recyclable. They are frequently used for high-temperature applications that may degrade plastic caps or plugs. Because paper is hygroscopic, excessive humidity changes or water contact can cause dimensional variation or warping.
Silicone rubber is made from cross-linked silicone based polymers reinforced with filler. Silicone rubber is very resilient, and boasts long service life through adverse environments. The operating temperature range for silicone rubber is wide, from -148°F to 600°F.

Features

Caps, grips, and closures may incorporate a number of features into their design which may be important for certain applications.

Feature	Example
Hanger tips allow for the hanging of tools or other items. They are sometimes integrated with handles or grips.	Image Credit: Alliance Plastics
Lift/pull tabs and rings allow caps to be easily removed. Pull plugs are designed for "through-hole" applications. They use a smaller diameter "pull section" to pull the plug until it is snug in the hole.	Image Credit: Parker Hannifin
Tear tabs are inserts which can be pulled for easy cap removal. When the tab is pulled, the cap tears away. Once removed, the cap cannot be reused.	Image Credit: Daemar Inc.
Vented caps are commonly used in the medical industry. The vent allows air flow during gas sterilization and prevents the cap from blowing off during extreme heat conditions.
Anti-roll caps are round caps with a square end to prevent tube or shaft from rolling.	Image credit: Brightwaterflyangler.com
Flange caps have flange edges included for easily removal or additional protection of the bearing surface. They also prevent accidentally pushing the plug all the way through the opening.	Image credit: MOCAP, Inc.
Knurled or faceted heads have perforations on the outside of the cap, allowing easier installation and removal, either by finger or wrench.	Image Credit: Quicksilver Radio Products
Slotted heads have a slot to allow the cap to be installed or removed with a screwdriver.	Image Credit: derbyking.com