Types of screws

See also:

• Types of bolts.
• Types of nails.
• Types of nuts.

[edit] Introduction

A screw is a type of fastener, usually made from metal, that commonly comprises a head at one end, and a point at the other, and a shaft shaped so that it can be turned into another material. The shape of the shaft is characterised by a helical ridge which is known as a ‘male thread’ (where the thread is external) or ‘female thread’ (where the thread is internal). Screws are typically used to hold materials or objects together, or to position objects.

The part of the screw that extends from the underside of the head to the tip is referred to as the ‘shank’ and is either fully or partially threaded. Threaded screws are intended to be driven into material or a pilot hole; partially or non-tapered screws are intended to be driven into a tapped hole.

Tools such as screwdrivers are commonly used to insert screws, and the majority are tightened by clockwise rotation.

[edit] Screws and bolts

The terms ‘screws’ and ‘bolts’ are sometimes used interchangeably, however, in simple terms, a bolt passes through a material and into a nut on the other side to bolt items together, whereas a screw threads directly into a material.

Both screws and bolts are often made of steel, and where resistance is required to weather or corrosion, they may be galvanised, or stainless steel, brass, zinc or titanium may be used.

For more information, see Types of bolts.

[edit] The history of screws

During the Middle Ages, wood screws emerged, with handcrafted metal screws finding applications in woodworking and carpentry. These early screws were individually crafted and often used with matching nuts.

The Industrial Revolution brought significant advancements in screw manufacturing. In the 1760s, the first automated screw-making machine was invented by Englishman Jesse Ramsden, which revolutionised the production of screws and made them more affordable and widely available.

In the 19th century, the development of mass production techniques and the standardisation of screw threads accelerated the use of screws in many various industries. This standardisation included defining specific thread profiles, pitch, and diameters, which allowed screws and nuts from different manufacturers to be interchangeable.

In the 20th century, screws continued to evolve with the development of new materials and manufacturing techniques. Different types of screws were introduced, such as self-tapping screws, machine screws, and specialised screws for specific applications such as electronics, construction, and aerospace.

Today, screws are ubiquitous and play a crucial role in many industries and technologies. Manufacturers have continued to explore and refine screw designs for specific purposes. For example, advances in robotics and medicine have led to the development of micro-screws for delicate and precise applications.

[edit] Types of screw

There are many different varieties of screw which are selected based on the particular requirement or the materials involved. Some of the most common types include:

[edit] Wood screw

Typically designed with a partially-unthreaded shank and used to attach pieces of timber together.

[edit] Concrete screw

Stainless or carbon steel and used for fastening materials to concrete.

[edit] Masonry screw

Often have a blue coating and are inserted to a pilot hole in masonry.

[edit] Double-ended (dowel) screw

Have two pointed ends and no head. Often used for making hidden joints between two pieces of timber.

[edit] Drive screw

Smooth, round or mushroom-headed with a reduced diameter shank.

[edit] Drywall screw

Often coated with black phosphate and designed with a bugle head. Used to attach drywall to timber or metal studs.

[edit] Eye bolt

A looped head designed to be used as an attachment point. Also used for attaching wires across building surfaces.

[edit] Decking screw

Longer screws which are used for fastening down deck boards.

[edit] Lag screw/bolt

A heavy-duty fastener.

[edit] Chipboard screw

Often wax-coated and used for fastening down chipboard flooring.

[edit] Mirror screw

Designed with a decorative dome or other cover to conceal the head.

[edit] Twinfast screw

Designed with two threads which enable it to driven twice as fast.

[edit] Security head screw

Designed with a head that is impossible to reverse, making it suitable for security applications.

[edit] Screw heads

Different types of heads include:

• Pan head: Rounded, high outer edge with a large surface area.
• Button/dome head: Cylindrical head with a rounded, dome-like top.
• Round head: Dome-shaped and used mainly for decorative purposes.
• Mushroom head: The dome has a lower profile that is designed to prevent tampering.
• Countersunk/flat head: Conical head with a flat outer face and a tapered inner face.
• Oval/raised head: Countersunk bottom and rounded top, often used decoratively.
• Bugle head: A smooth transition from the shank to the angle of the head.
• Cheese head: A disc with a cylindrical outer edge.
• Fillister head: Cylindrical with a slightly convex top surface.
• Flanged head: Can be any style but has the addition, at the base of the head, of an integrated flange which means it does not require a washer.

[edit] Related articles on Designing Buildings

• Construction equipment.
• Construction staples.
• Construction tools.
• Dry lining.
• Fittings.
• Fixings.
• Fixture.
• Furniture, fixtures and equipment.
• Nails - a brief history.
• Off-site prefabrication of buildings: A guide to connection choices.
• Strap.
• Structural steelwork.
• Types of bolts.
• Types of fixings.
• Types of nails.
• Types of nuts.
• Wall plug.