Marine Machine Screw

Specifications and Measurements Of Marine Machine Screw

Machine screws come in different specifications to accommodate various needs. They are available in coarse (UNC) and fine (UNF) threads, with right-hand threads being the standard (clockwise to tighten). The size (diameter) ranges from #0 (very small) to #12 and 1/4″ to 1/2″. There are nine common head styles, including two countersunk styles, and four drive styles. Three common materials used for these marine screws are also available.

Measurements for machine screws depend on the head style. For flat heads, the length is measured from the top of the head to the tip of the thread. Oval heads are measured from the edge where the dome top meets the sloping bearing surface to the threaded tip. Other head styles like Binding, Fillister, Hex and Hex Washer, Pan, Round, and Truss are measured from under the head to the screw’s tip. Length is specified in fractional inches.

Marine Machine Screw Size Chart

Marine Machine Screws Material

In marine applications, both bronze and stainless steel machine screws offer specific advantages due to their unique properties.

Bronze Machine Screws

• Boat Building: Bronze machine screws are commonly used in boat building for securing various components and fittings due to their corrosion resistance and antifouling properties.
• Deck Hardware: In marine deck hardware applications, bronze screws are preferred for their durability and resistance to corrosion.
• Decorative Fittings: Bronze machine screws are often used in decorative fittings on boats and ships due to their aesthetic appeal.

Stainless Steel Machine Screws

• Boat Hardware: Stainless steel machine screws are commonly used in boat hardware applications, such as securing cleats, hinges, and railings.
• Marine Structures: Stainless steel screws are used in constructing marine structures like docks, piers, and marinas due to their durability and resistance to corrosion.
• Below-Waterline Fittings: Stainless steel machine screws are often used for below-waterline fittings where corrosion resistance is crucial.

Head Types Of Marine Machine Screws

Head Types of Marine Machine Screws:

• Binding Head: The binding head features a low-profile, rounded top with a wide bearing surface. It is designed to distribute the load evenly and provide a secure connection. Binding head machine screws are commonly used in applications where a low-profile head is desired.
• Fillister Head: The fillister head has a slightly rounded top with a cylindrical shape. It offers a larger bearing surface than flat head machine screws, providing increased resistance to pull-out forces. Fillister head machine screws are often used in applications where a flush or countersunk appearance is not required.
• Flat Head: Flat head machine screw has a flat top surface with a conical bearing surface angle of 82°. It is designed to sit flush or slightly below the surface when installed, creating a neat and finished appearance. Flat head machine screws are commonly used when a flush finish is desired or when countersinking is required.
• Hex Head & Hex Washer Head: Hex head screws have a hexagonal head with six flat sides, allowing for easy and secure tightening using a wrench or socket. Hex washer head machine screws have a built-in washer-like flange under the head, providing additional bearing surface and eliminating the need for a separate washer. Both hex head and hex washer head screws are known for their high torque resistance and are widely used in marine applications.
• Oval Head: Oval head screws have a rounded top with a tapered, slightly flattened shape. The oval head provides a decorative appearance while still offering a countersunk feature for flush installation. Oval head screws are commonly used in applications where a decorative and low-profile head is desired.
• Pan Head: Pan head machine screws have a rounded, slightly domed top with a flat bearing surface. The pan head design offers a larger contact area, providing increased resistance to pull-out forces. Pan head screws are versatile and commonly used in a wide range of marine applications.
• Round Head: Round head marine screws have a domed top with a slightly larger bearing surface compared to pan head screws. The round head design provides a decorative appearance and increased strength. Round head screws are commonly used when a decorative finish and higher load-bearing capacity are required.
• Truss Head: Truss head machine screws have a low-profile, wide head with a rounded top and a flat bearing surface. The truss head offers a larger contact area and increased resistance to pull-through forces. Truss head screws are often used in applications where a wide bearing surface and high strength are necessary.
• Miscellaneous: This category includes various specialized head types that may be specific to certain applications or industries. These can include specialty heads like socket head, button head, or flange head screws, among others.

Usage Tips and Considerations Of Marine Machine Screw

To create a countersunk recess for flat and oval heads, it’s important to use a matching countersink with the appropriate angle (82° or 100°). The body diameter of the countersink should be equal to or greater than the head diameter to ensure a uniform bearing surface.

Machine screw flat washers can be used to increase the bearing surface of the screw’s head or nut. This is particularly useful when working with soft materials or oversized/irregular-shaped holes.

In addition, slotted flat head and slotted round head machine screws are sometimes referred to as stove bolts when supplied with hex nuts, offering versatility in certain applications.