Lock washers don't work?

[bcp]

I was looking for some information on when to use which type of lock washer: split, internal tooth, and external tooth.

I found good material on the toothed ones (use internal with small heads).

On split washers, several comments showed up that they didn't work, such as this:
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From:
http://www.boltscience.com/pages/helicalspringwashers.htm

"Helical spring lock washers have been in use for well over 100 years. They are still used on many applications in the belief that they will will "lock" the nut/bolt to the joint and prevent loosening. The body of evidence, based upon both experience and experimental results, is that they do not prevent loosening and can be shown to actually speed up the rate of loosening in many cases. "

(Interesting videos linked at page)

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More searching found a NASA report:

http://gltrs.grc.nasa.gov/reports/1990/RP-1228.pdf

Recommendations are usually for using lock nuts or bolts of various types, and not lock washers.

I've been using mostly split lock washer on machinery most of my life, and some have loosened. Maybe I'll start using toothed ones more.

What do you think?

Bruce

 

[k0ua]

Well, its like a lot of things I was taught in school that later proved to be false. I have always wondered why sometimes fastners with spring washers came loose anyway, I knew they were not much good, but continued using them because they are cheap and I was always "told" to. I also knew that nylock or the kind of bolt head with the ridges that catch when it is loosened were very good, but rarely use them because of the cost/availability. Oh well live and LEARN! Thanks for the info.:thumbsup:
James K0UA

 

[doall]

I hate nylon nuts. but have always had good luck with split lock washers. If the nut loosens a fraction the edge should come up a touch and bite into the nut on one side and the base material on the other(but I don't believe that either). So for me I guess lock tite is the best option. or crown bolts and cotter pins. I know i will continue to use split lock washers though.

 

[ray66v]

My brother is an engineer at the same NASA facility, so I knew about this when it was researched, decades ago.

I have thrown them away since.

However, like many old traditions, using lock washers, still won't die.

 

[Baby Grand]

Weather or not they will work will depend on a lot of things:

Installation torque.
Coeffient of friction between the threaded parts.
Coeffient of friction between the materials contacting the helical washer.
The hardness of the materials contacting the helical washer.
The pitch of the thread.
The amplitude and frequency of the vibration.
If the bolt loses proload due to reaction loads or thermal loads.
Probably a few I have overlooked.

In the case of space vehicles (what NASA does best) they are a poor choice. In the case of an adjusting bolt on a rear blade, they seem to work fine for me. Pick your poison carefully.

-Jim

 

[Mickey_Fx]

Interesting topic. I see that someone mentioned Loc-Tite. I'm a fan of these types of thread lockers. They do come in various strengths and one should be knowledgeable in which is the correct one for the application.

One area where they are especially good is in applications where rust/corrosion is an issue. Properly applied the thread locker will seal the threaded area between the nut and bolt. Corrosion then can't form so you don't end up fasteners that can't be disassembled.

 

[SPYDERLK]

Split lock washers can be very effective when the split point is designed so that it bites in. I have had just snugly tightened temporary fastenings bite both sides scoring the metal surfaces as the nut is removed. I have seen them bite enuf in a long term joint that the washer is unwound and destroyed during disassembly. A lock washer under both heads is totally effective if they bite. Still, when I service a joint I take them off and replace with high strength flat washers and tighten the joint to the top limit of torque or a little more. The larger flat washer spreads the intense clamp point a little, stabilizing the assembly and reducing the crack potential. A truly stable joint wont loosen.
larry

 

[BHD]

this is my take and understanding on Lock washers,

If one torques the bolt properly and the bolt is properly sized, is the best way to keep the nut on tight,

the reason why a bolt looses it because it moves, to torque a bolt properly, one tightens the bolt to where it has all the stretch removed yet not stretching it to a point of failure,

if it tightened to less than torque specification the bolt will stretch and move thus giving it opportunity to loosen,

about the only location where lock washers are used in abundance is in agriculture,

and I think the reason is that bolts are not torqued the majority of the time, and in many applications in flexing frames and to hold on tillage tools and so on is that there is frame flex, and there is dirt and wear, that keeps one from properly torquing the bolt correctly, and so many bolts in Ag related situations the bolts would not work for the designed purpose if they were torqued to proper specifications,
the lock washers are springs and have edges to bite the face, and the bolt or nut,

and I am under the impression that some lock washers actually hinder the proper torquing of the bolt,

(we have a old fork lift, and we could not keep the bolts on the frame to the axle tight about ever few weeks tighten them up, I finally bought a planetary gear head torque multiplier Torque Multiplier | Torque Wrenches | Northern Tool + Equipment and then used the 3/4 torque wrench to tighten them to estimated requirements, and they have not loosened since),

 

[SPYDERLK]

Interesting topic. I see that someone mentioned Loc-Tite. I'm a fan of these types of thread lockers. They do come in various strengths and one should be knowledgeable in which is the correct one for the application.

One area where they are especially good is in applications where rust/corrosion is an issue. Properly applied the thread locker will seal the threaded area between the nut and bolt. Corrosion then can't form so you don't end up fasteners that can't be disassembled.

Very good points. I use them too. #638 is my favorite for hi strength bolting. Very strong, but loses enuf strength at 200-300F to be readily removed without damage to rubber or other heat susceptible stuff.
larry

 

[brandoro]

I'm a fan of chemical locking as well. Loc-tite 242 is my most used. One advantage I like is that I always have the right size.
I occasionally use Ny-lock nuts as well but don't always have the right size. Generally use those on things I don't expect to need to disassemble.