How to prevent bolts subject to everyday machine vibration from loosening
How to prevent bolts subject to everyday machine vibration from loosening
(OP)
Hi
How do I prevent structural steel member bolts subject to machine vibration from loosening? I did some research online, I found this wedge lock washer and castle nuts. Are those good enough? Is preloading the bolts better? What do you guys usually do?

Thanks
How do I prevent structural steel member bolts subject to machine vibration from loosening? I did some research online, I found this wedge lock washer and castle nuts. Are those good enough? Is preloading the bolts better? What do you guys usually do?

Thanks
RE: How to prevent bolts subject to everyday machine vibration from loosening
- Jam nut is (might be?) the cheapest/easiest/most reliable option I.e., 2 nuts stacked and tightened - standard nut and a jam nut. Or just 2 standard nuts would work I suppose.
- You can spec to foul/peen threads but that won't necessarily prevent the nut from "loosening" per se - but it will prevent them from coming all the way off the bolt. I use this for lightly loaded thru bolts.
- Red loctite. I've never spec'd it but some folks on here do.
- Pretensioning / SC. Never spec'd it for this particular reason. I'd hope they wouldnt loosen since we use them in slip crit framing connections, but those arent typically subject to constant vibrations.
- Nord-loc washers like you show above would also work.
Is this for a machine-to-structure connection? Or a standard framing connection (beam-girder, etc.) that is below a machine. Machine to structure connections are sometimes pretensioned by default.RE: How to prevent bolts subject to everyday machine vibration from loosening
They work great in machines. I'm not a structural engineer so I don't how how suitable they are for structures.
They're an order of magnitude more expensive than plain washers though, so it's easy to overdo it and drive the cost of the machine through the roof if you're not careful.
RE: How to prevent bolts subject to everyday machine vibration from loosening
TTFN (ta ta for now)
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RE: How to prevent bolts subject to everyday machine vibration from loosening
another day in paradise, or is paradise one day closer ?
RE: How to prevent bolts subject to everyday machine vibration from loosening
dold
It is standard framing connection beam to column. I will go for jam nuts and nord-lock washers.
RE: How to prevent bolts subject to everyday machine vibration from loosening
Some alternatives ; jam nut, Loctite Red , peening or the use of spherically seated washers with hardened nuts
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I would prefer jam nuts or the use of spherically seated washers with hardened nuts
RE: How to prevent bolts subject to everyday machine vibration from loosening
another day in paradise, or is paradise one day closer ?
RE: How to prevent bolts subject to everyday machine vibration from loosening
For a standard steel connection a jam nut won't be detrimental but you will often find that A325 bolts do not have a long enough thread length to accommodate them (increasing the length of the bolt will often cause the first nut to bottom out on the shoulder of the bolt before properly clamping the connection), they will just be an added cost that does nothing to improve the performance of the joint and cause questions and issues come erection time.
The RCSC/AISC specifically requires pretensioning bolts in joints that are "subject to significant load reversal" (i.e. vibration) for just this reason - to prevent loosening.
RE: How to prevent bolts subject to everyday machine vibration from loosening
I would use Nordlock washers they are very good however they are expensive and so it sdepends very much how many joints you have this problem with.
Do you have any information about the actual joint subjected to the vibration? You can preload the bolts to withstand the variation of load but without knowledge of the vibration what would you tighten them too.
“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein
RE: How to prevent bolts subject to everyday machine vibration from loosening
RE: How to prevent bolts subject to everyday machine vibration from loosening
Is a bad choice and the thinner nut is on the bottom, if used. I often use Loctite 263 (Red) and have for decades... great stuff.
https://www.boltscience.com/pages/twonuts.htm
Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
-Dik
RE: How to prevent bolts subject to everyday machine vibration from loosening
If there is one place where a fine, exacting German reputation is on the line, its ensuring reliability of its military machines.
I disagree with the statements above that "you can drive the costs through the roof" by specifying NORDLOCK devices ... What is the cost when the joint comes apart ?
According to the vendor, NORDLOCKS can be repeatedly assembled and broken down... I believe them ... They have test data you can request
I have specified RED LOCKTITE over the years and it seems to be favored by anyone with an automotive background.
Two methods not specified above are:
1) Tack/spot Welded threads (a good method when a visual QA/QC is required on plain carbon steel nuts and bolts)... cannot be disassembled
2) Drilled and wired nuts/bolts (favored for decades by NASA and aerospace engineers) obvious, positive and cannot be disassembled.
There is no one "best" method for everyone.... the only best method is the one that suits your bolted joint design, metallurgy, coatings and needs of the future
MJCronin
Sr. Process Engineer
RE: How to prevent bolts subject to everyday machine vibration from loosening
Of course you're going to use them if it's critical to use them.
I was just saying that the cost of Nordlocks isn't all that negligible (as opposed to plain washers), so one needs to be mindful of that fact and not use Nordlocks everywhere simply because they exist. :)
Not all joints are critical and not all are in danger of coming apart.
I've seen people stack up thousands of dollars worth of unnecessary cost simply because they automatically assumed washers were cheap (easy mistake to make since 99% of time they are negligibly cheap).
RE: How to prevent bolts subject to everyday machine vibration from loosening
Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
-Dik
RE: How to prevent bolts subject to everyday machine vibration from loosening
MR. MJCronin (Mechanical) has nailed it with his perfect wording.