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Solution Summary: Quick-Threading Lock Nuts

When you tighten a standard lock nut around the thread on a long rod, you have to twist your hand, wrist, and forearm over and over. Making these twisting movements can strain the muscles and tendons in your hand, wrist, and elbow. The strain can become more serious if you do this work a lot and you repeat the same movements for a long period of time. You can eventually develop pain and even a serious injury.

Your chance of injury depends on the amount of finger pressure you use to hold the nut, the distance the nut is threaded, and the number of nuts threaded. Working in positions where you have to reach above your shoulders to thread the nut increases your chance of injury.

The photos below provide an example the problem (conventional tightening of nut on all thread) and a solution (slip on lock nuts):

Description:

When you tighten a standard lock nut around the thread on a long rod, you have to twist your hand, wrist, and forearm over and over. Making these twisting movements can strain the muscles and tendons in your hand, wrist, and elbow. The strain can become more serious if you do this work a lot and you repeat the same movements for a long period of time. You can eventually develop pain and even a serious injury.

Your chance of injury depends on the amount of finger pressure you use to hold the nut, the distance the nut is threaded, and the number of nuts threaded. Working in positions where you have to reach above your shoulders to thread the nut increases your chance of injury.

The photos below provide an example the problem (conventional tightening of nut on all thread) and a solution (slip on lock nuts):

 worker using quick threating lock nut      quick threading lock nuts stand alone

There are two types of quick-threading lock nuts—Slip-On® Lock Nuts and Morton Button Thread Nuts.  The Slip-On® types have two parts.  You twist the two sections of the nut apart until the slot is open, then place the nut on the all-thread rod where you need it.  Then twist the two sections together again until the slot is closed and the sections are snug against each other. Finally, tighten the nut with a wrench until the openings on the two sections face in opposite directions.

Morton Button Thread Nuts slide up and down the all-thread rod.  You first push the button to loosen the nut from the thread.   Then slide the nut to the spot you want. Let go of the button to make the nut re­connect with the thread.  Then tighten it as you would any nut.


Risks Addressed:

Strain to the muscles and tendons in your hand, wrist and elbow.


How Risks are Reduced:

Use a quick-threading lock nut.  Depending on the type of nut, these can either snap onto an all-thread rod at any position, or slide up and down the rod freely.  They eliminate the repeated hand, wrist, forearm, and elbow twisting.  They can also reduce the time you spend working above your shoulders because they go on faster.


Quality of Evidence (Risk Reduction):

  • Safety and health experts believe there is a risk reduction.

Quality of Evidence Explanation (Risk Reduction):

If you reduce exposures such as the number of repetitions, frequency, and force in a repetitive wrist and finger movement, and reduce the duration of work overhead, then the probability of injury should be reduced.


Effects on Productivity:

Using quick-threading lock nuts should reduce the strain on your hand, wrist, and forearm. It should therefore lessen the chance of pain and musculoskeletal injury. Because you spend less time working above your shoulders, there is also less overall strain on your shoulders, neck, and back during a shift.

In addition, these nuts should lead to a gain in productivity because they take less time. They make certain kinds of work much easier, such as threading nuts in locations that are diffcult to access. Quick-threading lock nuts may not be appropriate for all jobs, and their use may require the approval of the building owner, architect, engineer, or general contractor.


Quality of Evidence (Effects on Productivity):

  • Manufacturers or vendors have reported an increase in productivity.
  • Safety and health experts believe there is an increase in productivity.

Quality of Evidence Explanation (Effects on Productivity):

Advancing a threaded-rod hanger for pipes, ducts, or electrical trays or conduit can be awkward and time consuming.  Rod end damage can cause cross-threading, threads may be damaged, or the rod may be inaccessible.  Using quick-thread lock nuts will increase productivity if used in appropriate applications.


Sources:

Albers, James T., and Estill, Cheryl F.  Simple Solutions: Ergonomics for Construction Workers.  DHHS (NIOSH) Publications.  March 2007.  http://www.cdc.gov/niosh.  To view the Table of Contents for the Simple Solutions Document, please visit:  http://www.cpwr.com/simple.html.  Please send requests for copies of this publication to cdcinfo@cdc.gov, referencing document number 2007-122.

 

Availability

Where to Get It

See manufacturers' websites for detailed specifcations, including torque and tensile strength ratings.

Approximate Cost

Slip-On Lock Nuts start at $2-3 each, depending on diameter.  Metric sizes are available.  Morton Button Thread Nuts start at approximately $6 each.

 

Return on Investment

To calculate the return on investment (ROI) for your specific application, please visit our Return on Investment Calculator. While a specific ROI example has not been developed for this particular solution, the ROI Calculator provides a useful tool and guidance on how to generate your own on investment analysis.

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