Design World

  • Home
  • Technologies
    • 3D CAD
    • Electronics • electrical
    • Fastening & Joining
    • Factory automation
    • Linear Motion
    • Motion Control
    • Test & Measurement
    • Sensors
    • Fluid power
  • Learn
    • Ebooks / Tech Tips
    • Engineering Week
    • Future of Design Engineering
    • MC² Motion Control Classrooms
    • Podcasts
    • Videos
    • Webinars
  • LEAP AWARDS
  • Leadership
    • 2022 Voting
    • 2021 Winners
  • Design Guide Library
  • Resources
    • 3D Cad Models
      • PARTsolutions
      • TraceParts
    • Digital Issues
      • Design World
      • EE World
    • Women in Engineering
  • Supplier Listings

Screw handedness: When do you need a left-handed screw?

By Danielle Collins | February 14, 2022

Share

Just like people, ball and lead screws can be either right-handed or left-handed. But in screw terminology, handedness indicates the direction in which the nut moves relative to the direction of the screw’s rotation. By far the most common version is the right-handed screw, in which the nut moves toward you when the screw is rotated clockwise. But left-handed versions, in which the nut moves away from you when the screw is rotated clockwise, are also available — and useful in some applications.

screw handedness
With a right-handed screw (top) the nut moves toward you when the screw is rotated clockwise.
With a left-handed screw, the nut moves away from you when the screw is rotated clockwise.
Image credit: McMaster-Carr

The prevalence of right-handed power transmission screws follows from the domination of right-handed fastening screws. Fastening screws are thought to have been developed with right-handed threads — which tighten when turned clockwise — because most people are right-handed, so their right hand supinates clockwise, allowing them to apply more torque (to tighten the fastener) in this direction.


To demonstrate supination and its relationship to tightening, start with your right hand in a loose fist, like you’re grasping something, with the back of your hand facing up and your thumb on the left side. Then turn your hand to the right so that the palm side is facing up and your thumb is on the right. This is supination of your right hand, and the direction for tightening a conventional, right-handed fastening screw.


screw handedness
Although right-handed screws are most common, left-handed screws are available from some manufacturers.
Image credit: Accu Ltd.

The availability of left-handed ball screws is relatively limited, although most manufacturers offer a few sizes and designs in both left- and right-handed versions. Lead screws, on the other hand, are commonly available in a variety of designs and sizes with both left- and right-hand options. There’s no performance difference between left- and right-handed screws — the screw’s handedness only affects the nut’s direction of travel when the screw is turned in either direction. But it’s important to note that you can’t use a left-handed nut on a right-handed screw, or vice-versa.


So why would you use a left-handed lead or ball screw when you can use a conventional right-handed screw and just reverse the direction of rotation of the motor? One common reason is to drive two screws from one motor — often via a gear or other transmission component with dual output shafts.

left- and right-handed screw
Screws with both left- and right-hand threads are useful in actuators that need to produce opposing motions.
Image credit: igus

Some manufacturers even produce combination left- and right-handed screws, in which a single screw shaft has been machined with left-handed threads on one end and right-handed threads on the other end. Thus, when a motor drives the screw in one direction, the two nuts move toward each other. And when the motor reverses direction, the nuts move away from each other. This design is especially useful in dual-motion linear actuators.

dual-motion linear actuator
Some linear actuators incorporate both left- and right-handed screws, welded or mechanically joined and driven by a single motor. Each end of the screw has a nut, so the loads move toward or away from each other as the screw rotates.
Image credit: THK

Filed Under: Linear Motion Tips

 

Related Articles Read More >

Machining Center Manufacturing MCM S.P.A. to exhibit at this year’s IMTS
New size 17 hybrid linear actuator features enhanced performance
High-precision three-axis positioning stages feature four motor options
Programmable linear actuator features stroke to 100 mm

DESIGN GUIDE LIBRARY

“motion

Enews Sign Up

Motion Control Classroom

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

  • Global supply needs drive increased manufacturing footprint development
  • How to Increase Rotational Capacity for a Retaining Ring
  • Cordis high resolution electronic proportional pressure controls
  • WAGO’s custom designed interface wiring system making industrial applications easier
  • 10 Reasons to Specify Valve Manifolds
  • Case study: How a 3D-printed tool saved thousands of hours and dollars

Design World Podcasts

May 17, 2022
Another view on additive and the aerospace industry
See More >
Engineering Exchange

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

Connect, share, and learn today »

Design World
  • Advertising
  • About us
  • Contact
  • Manage your Design World Subscription
  • Subscribe
  • Design World Digital Network
  • Engineering White Papers
  • LEAP AWARDS

Copyright © 2022 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
    • 3D CAD
    • Electronics • electrical
    • Fastening & Joining
    • Factory automation
    • Linear Motion
    • Motion Control
    • Test & Measurement
    • Sensors
    • Fluid power
  • Learn
    • Ebooks / Tech Tips
    • Engineering Week
    • Future of Design Engineering
    • MC² Motion Control Classrooms
    • Podcasts
    • Videos
    • Webinars
  • LEAP AWARDS
  • Leadership
    • 2022 Voting
    • 2021 Winners
  • Design Guide Library
  • Resources
    • 3D Cad Models
      • PARTsolutions
      • TraceParts
    • Digital Issues
      • Design World
      • EE World
    • Women in Engineering
  • Supplier Listings