Lock washer questions

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  #1  
Old 08-03-17, 08:17 AM
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Lock washer questions

I tried searching the Internet for answers and just became more confused. Specifically I would like to know when or how the different types of lock washers are used and the advantages or disadvantages of each type.

The types are the common split "spring" lock washer, the internal star lock washer, the external star lock washer and the Belleville washer.

For the first three I have read that none of them have any advantage over a properly torqued nut/bolt assembly but if that is true then why use them at all? Star washers are obviously more expensive and if they provide no more benefits than a split washer then why use them?

Belliville washers are a breed apart and I can't say I have ever seen them used except on electrical connections.
 
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Old 08-03-17, 09:23 AM
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Personally I prefer lock nuts to lock washers. The problem I see with lock washers is if they ever loosen they no longer serve their function. Lock nuts will not just spin off the way nuts held with lock washers will if they become slightly loose.

More on subject to me the split spring washer is better because it provides constant pressure even with slight expansion and contraction of the metal. Star washers seem to do little more than provide slight friction.
 
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Old 08-03-17, 09:43 AM
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Star washers seem to do little more than provide slight friction.
Although they look ineffective.... they are extremely effective.

I had a mobile electronics shop for many years. Installations was a big part of the business. I used star washers on almost every nut and bolt. I used predominately internal tooth and but also internal/external tooth and external tooth. There was always a star washer on a ground connection.
 
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Old 08-03-17, 12:16 PM
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There was always a star washer on a ground connection.
Yep, every electrical "box" (Bud, Hoffman, etc.) I have ever seen used a star washer under the equipment ground lug although a partial reason is to scratch through the paint to make a good contact.

Then there are Keps nuts that have the star washer permanently attached. For my lawn tractor project I have mostly been using serrated flange nuts but sometimes because of space limitations I can't. Also, I wonder how well a serrated flange nut works when it is pressing up against a flat washer. For my motor mount I have three of the four mounting studs going through slots to allow me to move the motor for belt tightening. The slots have a heavy flat washer on each side and it is this specifically I am asking about for lock washer usage.
 
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Old 08-03-17, 02:52 PM
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What?! You are also excluding wavy, curved disk, and Nord-lock washers from the discussion?
 
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Old 08-03-17, 04:02 PM
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If you want "for sure" locking use a nylock nut. Washer can be used for spacing. But the star washers are must for electrical and electronic assembly.
 
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Old 08-03-17, 10:24 PM
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Vic, I had to look up the Nord-lock, I've never seen anything like that. I am assuming the curved disc is the same as a Belleville and the wave is something I associate more with keeping a small, but constant tension on an assembly.

As I stated, it is my opinion and experience that star/toothed lock washers are as much for electrical continuity as they are for actual bolt locking. The split lock washer is the least expensive and the Belleville is for holding a specified torque despite expansion and contraction, mostly with electrical lug connections that heat and cool depending on the current flow.

The serrated flange nuts I am using seem to me to be far superior to a split lock washer. I can turn the bolt into the flanged nut and then not be able to turn the nut at all using a normal length wrench but the bolt itself still unscrews with relative ease.

However, no one has truly answered the question, are lock washers even necessary or is simply torquing the nut along equally reliable as using any specific lock washer?
 
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Old 08-03-17, 11:41 PM
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The curved disc is more like a flat washer with the ends bent upwards, sort of like half a Belleville I guess.

As to whether they are necessary...I would say yes in some instances, esp parts that are subject to expansion and contraction as well as vibration, but cannot or should not be torqued to a high value.

I'd use this as an example. The wooden stakes on a stake bed truck, bolted to metal rails or even just to wood rails if it's old school. You can use carriage bolts with washers and nuts and tighten them down hard til the washer is below the surface...but I'll all but guarantee the nuts will loosen after a year or less. Some of the nuts may even be missing. Put a split, wavy, or curved disc lock washer under the nut and your problem is greatly reduced if not eliminated.

Now, things like engine head bolts, you actually torque so much they stretch and provide their own lack washer type clamping force which takes care of the expansion/contraction issue.

I agree completely on the star type as to use in electrical. It would seem that the flanged nuts you are using use a similar method, though not for the same reason. The serrations "bite" in to the substrate and prevent movement while the bolt could still turn. Since the bolt has a greater mass and has more friction on it than the nut (normally), it's unlikely it would loosen on it's own in most uses.

And then of course there are those cases where failure is not an option and they use lock nuts AND safety wire.

I don't like nylock nuts normally, since they have to be cranked off all the way with a tool instead of being spun off by hand after initial loosening. They have their places of course, just not that many...for me. Same for what I think they call top-lock nuts? Where they actually have a semi-interferance fit at the end?
 
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Old 08-04-17, 03:41 AM
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I don't like nylock nuts normally, since they have to be cranked off all the way with a tool instead of being spun off by hand after initial loosening.
I have to agree with you on this point. It seems that there is a false sens of security with nylocks since they are becoming more common in many situations that normally would not have them. Many of the cheap, pre-drilled, assemble it yourself furniture will use nylocks.
 
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Old 08-04-17, 10:29 AM
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I do like Nyloks, but only in very limited usage. Some areas I will use a standard nut and then add a thin lock nut if it is critical. The self-locking nuts that have some kind of "upset" to the threads do have their place. I used them on the front axles where I had to have a bearing preload (tapered bearings) and yet not have to use two nuts and trying to hold the main while tightening the jam nut.

So for the most part I am using the serrated flange nuts and no lock washers at all on the more critical components. Less critical I might forego any lock washers and use either tapped holes or just plain nuts.

I have to go get my eyeballs examined in a couple of hours but maybe I can post a picture of the motor mounting (with the slotted holes) that was behind this question later tonight or tomorrow.
 
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