We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.
Electrical

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

What Is a Screw Terminal?

By Geisha A. Legazpi
Updated: May 17, 2024
Views: 10,159
Share

A screw terminal is a device that can connect two or more conductors using multiple-twist fasteners. The conductors to be connected by the screw terminal are usually mounted with terminal crimp-type lugs that secure the bare conductor ends. The screw terminal can be found where there is electrical service and inside household, commercial, and industrial electrical equipment.

Electrical connectors include various types of plugs and sockets that allow anyone to connect or disconnect appliances. The screw terminal is a connector that may be mounted right on equipment chassis, brackets, or printed circuit boards, and is used for special purposes such as internal wiring and maintenance procedures. Screw terminals require that the bare wire be twisted, tinned, or installed with terminal crimp lugs or solder lugs, and as a best practice the copper surface of the bare wire should be coated with a layer of tin-lead alloy for protection from oxidation. The crimp-type terminal lug terminates the wire with a rigid metal eyelet that may be mounted on a terminal block. Without the terminal lug, the mechanical strength and connect/disconnect durability of the bare wire are not enough.

The barrier strip and terminal strip are each a set of screw terminals that come in pairs. The terminal strip, which may be either solder type or screw type, does not provide a barrier between terminals. The barrier strip usually has insulator barriers between terminals to prevent accidental shorting.

In modular wiring design, the screw terminal provides the flexibility and accessibility needed to avoid having to disconnect and reconnect parts of the circuit. For instance, there are several test points needed when testing a motor controlled by a relay that is controlled by a start-stop switch. The test points are readily available for voltage testing by a digital voltmeter, and the faulty one may be isolated easily.

The screw terminal may also be used in mobile transport. This application requires locking washers that ensure the screw does not loosen due to vibration. The luster terminal is also well suited for both fixed and mobile installations due to compactness and covered conducting portions. Setscrews are used in the luster terminal where the screw presses on bare or tinned wire.

A substitute for the screw terminal is the wire nut, which is a piece of insulator with a conductive gripper on the inside. It is used as a cap for wires that have been twisted together side-by-side. The exposed conductor is inserted inside the wire nut, which is twisted clockwise to secure the wire until there is no exposed conductor. Temporarily removing the wire nut allows for maintenance measurements and troubleshooting.

Share
About Mechanics is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
Share
https://www.aboutmechanics.com/what-is-a-screw-terminal.htm
Copy this link
About Mechanics, in your inbox

Our latest articles, guides, and more, delivered daily.

About Mechanics, in your inbox

Our latest articles, guides, and more, delivered daily.