Design World

  • Home
  • Technologies
    • ELECTRONICS • ELECTRICAL
    • Fastening • joining
    • FLUID POWER
    • LINEAR MOTION
    • MOTION CONTROL
    • SENSORS
    • TEST & MEASUREMENT
    • Factory automation
    • Warehouse automation
    • DIGITAL TRANSFORMATION
  • Learn
    • Tech Toolboxes
    • Learning center
    • eBooks • Tech Tips
    • Podcasts
    • Videos
    • Webinars • general engineering
    • Webinars • Automated warehousing
    • Voices
  • LEAP Awards
  • 2025 Leadership
    • 2024 Winners
    • 2023 Winners
    • 2022 Winners
    • 2021 Winners
  • Design Guides
  • Resources
    • Subscribe
    • 3D Cad Models
      • PARTsolutions
      • TraceParts
    • Digital Issues
      • Design World
      • EE World
    • Educational Assets
    • Engineering diversity
    • Trends
  • Supplier Listings
  • Advertise
  • Subscribe

What is the difference between a lag and a metal screw?

By Michelle Froese | December 23, 2020

Written by Jody Muelaner

A typical square headed lag screw (left) and a countersunk head metal screw (right).

Lag screws and metal screws are two types of self-tapping fasteners. A lag, known in the UK as a coach screw, is primarily designed to be installed into wood. And, as the name suggests, metal screws are intended to be screwed into sheet metal.

Lag screws are sturdy and often have an externally driven square or hex drive head, and features coarse threads and a tapered point. Lag screws are much more heavy-duty than other wood screws that are fitted with slotted or Pozidriv heads. Its name derives from its original use in securing barrel staves, also known as lags.

This type of fastener requires a hole drilled at the same diameter as the shaft of the screw. A gimlet point helps pull the screw into the hole to tap its own thread. It can also be used to fix masonry using either a lag shield or nylon anchor.

The typical sizes available are between 1/4 to 3/4 inches in diameter, and between 1 to 16 inches in length. The most common materials used are steel and stainless steel. Steel screws are often finished with hot-dip galvanizing or zinc plating.

In several cases, a construction screw can be used instead of a lag screw. It has a thinner shank, an internally driven head, and a fluted tip which negates the need for pre-drilling. In fact, construction screws have replaced lag screws in many applications.

Metal screws are versatile and have a fully threaded shank. These fasteners typically have fine threads, which are sharp and hardened to allow thread-forming. They also feature a tapping or thread cutting point, which is used in a pre-drilled hole or a self-drilling point.

A metal screw has a countersunk or non-countersunk head with the option of a wide variety of internal and external drive types, depending on the application. Its size is usually marked with a series of three numbers representing the diameter number, thread count per inch, and length in inches.

One type of metal screw that’s commonly used in roofing is a wood-to-metal self-drilling screw. It’s designed to affix soft materials, such as wood or cement board, to metal.

This type of fastener features a self-drilling point with wings further up the shaft. These wings follow the cutting clearance of a hole in the soft material but are destroyed when installed in harder metal. This screw provides a clearance drilling, tap drilling, thread tapping, and fixing solution in one operation.

You Might Also Like


Filed Under: Screws • nuts • bolts • rivets

 

LEARNING CENTER

Design World Learning Center
“dw
EXPAND YOUR KNOWLEDGE AND STAY CONNECTED
Get the latest info on technologies, tools and strategies for Design Engineering Professionals.
Motor University

Design World Digital Edition

cover

Browse the most current issue of Design World and back issues in an easy to use high quality format. Clip, share and download with the leading design engineering magazine today.

EDABoard the Forum for Electronics

Top global problem solving EE forum covering Microcontrollers, DSP, Networking, Analog and Digital Design, RF, Power Electronics, PCB Routing and much more

EDABoard: Forum for electronics

Sponsored Content

  • Widening the scope for machine tool designers with FORTiS™ enclosed encoder
  • Sustainability, Innovation and Safety, Central to Our Approach
  • Why off-highway is the sweet spot for AC electrification technology
  • Looking to 2025: Past Success Guides Future Achievements
  • North American Companies Seek Stronger Ties with Italian OEMs
  • Adapt and Evolve
View More >>
Engineering Exchange

The Engineering Exchange is a global educational networking community for engineers.

Connect, share, and learn today »

Design World
  • About us
  • Contact
  • Manage your Design World Subscription
  • Subscribe
  • Design World Digital Network
  • Control Engineering
  • Consulting-Specifying Engineer
  • Plant Engineering
  • Engineering White Papers
  • Leap Awards

Copyright © 2025 WTWH Media LLC. All Rights Reserved. The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media
Privacy Policy | Advertising | About Us

Search Design World

  • Home
  • Technologies
    • ELECTRONICS • ELECTRICAL
    • Fastening • joining
    • FLUID POWER
    • LINEAR MOTION
    • MOTION CONTROL
    • SENSORS
    • TEST & MEASUREMENT
    • Factory automation
    • Warehouse automation
    • DIGITAL TRANSFORMATION
  • Learn
    • Tech Toolboxes
    • Learning center
    • eBooks • Tech Tips
    • Podcasts
    • Videos
    • Webinars • general engineering
    • Webinars • Automated warehousing
    • Voices
  • LEAP Awards
  • 2025 Leadership
    • 2024 Winners
    • 2023 Winners
    • 2022 Winners
    • 2021 Winners
  • Design Guides
  • Resources
    • Subscribe
    • 3D Cad Models
      • PARTsolutions
      • TraceParts
    • Digital Issues
      • Design World
      • EE World
    • Educational Assets
    • Engineering diversity
    • Trends
  • Supplier Listings
  • Advertise
  • Subscribe
We use cookies to personalize content and ads, to provide social media features, and to analyze our traffic. We share information about your use of our site with our social media, advertising, and analytics partners who may combine it with other information you’ve provided to them or that they’ve collected from your use of their services. You consent to our cookies if you continue to use this website.