Notched Nut and Threaded Rod to Prevent Nut Loosening? 5

[Logan82]

Hi!
The contractor notched the nut and the threaded rod to break the threads to prevent nut loosening. There was no torque, no nut loosening prevention measure in the drawings (not mine). Has anyone encountered this method before? Are there any worries to have with this method or is this even a bonus? The nuts were torqued snug tight. It holds together 2 timber parts.

 

[dik]

Wrecking the threads is a common method...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Logan82]

Thank you for the information dik! Are there any danger of nut structural damage however?

 

[Enable]

LOL

As dik said we score threads to prevent back-off. We don't put the nuts into a blender. How does one even do what happened in the second picture?

As long as you have a few extra threads pass the nut it's fairly easy to score with a grinder. What has gone on there I have never seen. I would be concerned about the nut damage in your second photo.

CWB (W47.1) Div 1 Fabricator
Temporary Works Design

https://www.enable-inc.com/

 

[Logan82]

Honestly, while I can imagine a grinder cutting the nut in the first picture, I have no clue what the guy did to achieve the damage in the second picture loll. Thank you for your opinion Enable!

 

[dik]

Not likely... maybe if really high strength stuff... the distortion is a bit of a stress riser, but the force at that end of the nut is next to zero... I don't usually damage the nut, but the threads below (above?).

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

This is from my project notes:

-ALL FASTENERS, SUPPORTING MECHANICAL EQUIPMENT, WHERE THE NUTS ARE LOADED IN TENSION ARE TO BE SECURED USING LOCTITE 263 (RED) THREAD LOCKER OR THE THREADS SHALL BE PEENED TO PREVENT LOOSENING.
-HSS THROUGH BOLT FASTENERS TO CONFORM TO ASTM A307, GRADE B. THROUGH BOLTS FOR HSS TO BE FINGER TIGHT. TORQUE TO 2.3N-M (20IN-LBS) (DO NOT CRUSH HSS WALL) AND THREADS SECURED BY PEENING, ‘JAM NUTS’, OR LOCTITE ‘RED’ THREAD LOCKER.
-BOLTS FOR ‘SLIDING’ CONNECTIONS TO CONFORM TO ASTM A307, GRADE B, AND SHALL BE FINGER TIGHT. TORQUE TO 2.3N-M (20IN-LBS) (DO NOT CRUSH HSS WALL). SECURE BY PEENING, ‘JAM NUTS’, OR LOCTITE ‘RED’ THREAD LOCKER.

INSTALLATION OF ‘JAM’ NUTS:
THE INNER JAM NUT SHALL HAVE A THICKNESS OF NOT MORE THAN 75% OF THE OUTER NUT;
THE INNER NUT SHALL BE INSTALLED FIRST AND SNUGGED TO 50% OF THE TORQUE VALUE;
THE OUTER JAM NUT SHOULD BE INSTALLED SNUG TO THE INNER JAM NUT;
THE INNER NUT SHOULD BE RESTRAINED TO KEEP FROM ROTATING AND THE OUTER JAM NUT SHOULD BE FULLY TORQUED TO IT; AND
WRECK THE THREADS BELOW THE NUT.

and I add or subtract, depending on the circumstances.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dhengr]

Logan82:
My goodness, you don’t need a jackhammer or a pile driver to check/deform the threads on a bolt. Take a center punch and ding/deform the bolt thread immediately outside of the nut, without damaging the nut, and the nut can’t back off. This will not guarantee that the original bolt tension is maintained, but the nut won’t back off. The bolt and bolt threads are not highly stressed outside of the nut. I wouldn’t mess with the nut as shown in the photos, that is highly loaded in shear and circumferential tension and you are putting a big stress raiser into the nut, not a good idea.

 

[RobertJeffery]

While working as an ICC bolting inspector I have seen the requirement of deform the bolted assemblies to prevent back-off. Typically the engineer has suggested that a center punch be used "once or twice" to deform the metal at the juncture of the threaded item and the nut as long as the inspector could "catch a fingernail" on the thread of the threaded item passing through the nut. i.e. "Full Nut"

My $0.02

 

[Logan82]

Thank you dik, dhengr and RobertJeffery!

I wouldn’t mess with the nut as shown in the photos, that is highly loaded in shear and circumferential tension and you are putting a big stress raiser into the nut, not a good idea.

By saying "I wouldn’t mess with the nut as shown in the photos", do you mean you would replace the nut and the threaded rod? Or you would leave the nut there in this condition? Also I didn't understand this part of the sentence "that is highly loaded in shear and circumferential tension and you are putting a big stress raiser into the nut, not a good idea."

The threaded rods are mainly loaded in shear. They are not very utilized in tension.

 

[XR250]

@dik,

I always feels like I am getting yelled at by your notes

 

[MotorCity]

We typically deform the exposed threads. By damaging the nut, it may no longer be able to resist the forces in the rod. If the nut was nicked or slightly dented, I'd probably let it go, but from the close up photo it looks as if more than half of the wall of the nut is gone! It may or may not be ok, but if it were me I would not take the chance and ask the contractor to redo it.

 

[dik]

My notes are all upper case to match the notes on the drawing. Most drawings are upper case. I can't remember the last time I yelled... I'm not that sort... and other than headings, I don't bold or underline them... they're all important, none more important than others.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik