School me on proper use of lock (split) washers

[Angelfish]

I buy split washers by the hundred and I put them on things that I think make sense to have split washers, mostly things that I don't want to come apart on their own.

 

 I assume there's a right and wrong place for them.

 

On an engine for example.  Assorted generator brackets, starters, fuel pumps, oil pump housings, transmission bell housings, engine mounts, exhaust manifolds, carburetors.

 

Assembling the frame there's all sorts of little brackets and bits and pieces. 

 

Is there a predictable criteria when they are desirable and when not?

 

Edited January 23, 2023 by Angelfish (see edit history)

[Andy J]

I use them on all the examples you have listed.I don't put them on sheet metal fasteners or molding fasteners for fear of tightening them too much,possibly causing them damage.

 

My rule of thumb is if in doubt,use one. I'm not an expert by any means,but that's how I roll.

[dl456]

There's also the discussion about the proper lock washer for application. Internal star, external star or split.

Common sense but worth mentioning.

 

[31Buick96S]

The fastener representatives that serviced a shop I managed were fans of locking nuts or chemical thread locker. The Bowman rep gave me an engineering report that pointed out that a split washer effectively becomes a flat washer after it is tightened. They also pointed out that you had to be careful of the material that the washer was against to prevent fretting. Just some things to consider.

[Gary_Ash]

Check out boltscience.com. They quote results of vibration testing on bolted joints with and without split lockwashers. They conclude we are better without split lock washers, especially for joints subject to vibration.  This is a dilemma when we restore old cars that did use split lockwashers and we try to be original.  I have mostly given up using split lockwashers  and just torque the bolts to 90% of yield. This is easier on modern bolts, difficult on old bolts of unknown strength. Note that modern specs for head bolts call for torquing bolts beyond yield to produce permanent stretch but very high clamping forces.  Such bolts cannot be reused. 

[John E. Guitar]

This old NASA document gives a good outline on fasteners starting on page 6. Page 9 covers lockwashers.

 

https://ntrs.nasa.gov/api/citations/19900009424/downloads/19900009424.pdf

[hddennis]

This brings up a question I've always wondered about. When did lockwashers first appear on automobiles?

 

Howard Dennis

[37_Roadmaster_C]

5 hours ago, dl456 said:

There's also the discussion about the proper lock washer for application. Internal star, external star or split.

Common sense but worth mentioning.

 

This is one area I would like more information on.  I really like the star lock washers, but I do not know if I am using them properly.

 

Ok, I looked at the NASA document that @John E. Guitar linked to.  It has an amazing amount of information.  Well worth the read and saving as reference material.  The part on split lock washers is an eye opener!!!

Edited January 23, 2023 by 37_Roadmaster_C
better Info (see edit history)

[Angelfish]

To summarize the NASA document, it states that split (helical spring) washers are "useless for locking."  Well, talk about the earth shifting under my feet.  They didn't seem very impressed with star washers either, implying that they may be slightly better than nothing, but that is a step up from "useless."

 

On the plus side, I never did like the appearance of split washers, so I guess I'll skip them from now on.

[Nailbitten]

Quite interesting for sure. There isn't a doubt in my mind they know way more than i do but,my lawnmower blade has hit concrete,moles,voles,baby rabbits,rocks,stones and tree stumps and has never fell off,so i am going to keep using  lock washers when i sharpen the blades and reinstall them! Not broke,don't fix it.

[Andy J]

Come to think of it,after reading all these posts,I've had many things bolted together without lock washers and don't remember anything getting loose or coming apart. I believe if something got loose,it just wasn't tightened enough.

[Buick35]

cross threading is better than lock washers.

[R Walling]

 Quoted from the bible of Google,

 

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.

Helical Spring Washers (boltscience.com)

 

 Well, that solves it! I will no longer use lock washers, saving me a lot of money on my projects! 😊

[Angelfish]

33 minutes ago, Buick35 said:

cross threading is better than lock washers.

It works great for people who can't leave things alone, knowing it will never go back together if you touch it one more time is a good incentive to leave it alone,

[JFranklin]

I use split washers on applications that had them, but also add a drop of blue locktite for peace of mind!

[hddennis]

So nobody knows when lockwashers use started on automobiles?

 

Howard Dennis

[1912Staver]

I can't provide an exact date. But it must have been quite early.  Every machine I have worked on from the mid teens uses at least some. There is probably a patent showing when the first came to market. But researching the topic would probably be quite time consuming. They possibly pre date automobiles.

[1912Staver]

Another thing I have noticed, most of the currently available split washers seem to crack easily.  I expect the vast majority are produced offshore with little quality control.

[dodge28]

A split washer will flatten out when used. Effectively making it a flat washer. I think all depends on where they are used. I came across split washers completely flat after removing bolts. The split washers removed from my 28 DB was in good condition when I removed them. I cleaned in Vapo rust and reused. I think all depends on quality. I will use only flat washers on head bolts. Buying fasteners these days is like trading horses. unless you know precisely they are made in US or Canada.

In y working days the company had a tractor powered by a Detroit Diesel bolted to a Spicer 13 speed. Every 1000 miles or so it was in the shop. The transmission bolts became loose . The manager bought aircraft washers. They worked much better . If you know tractor engines you will know how the Detroit Diesel was famous for vibrations.    

[Nailbitten]

No positive manufactured date yet although the first patent 1922.Ford started using them in 1924.I'm sure they were around long before that.Early years they were blued steel,and a lot thicker.I found this article...A lock washer is 'Handed'...

A ring split at one point and bent into a helical shape. This causes the washer to exert a spring force between the fastener's head and the substrate, which maintains the washer hard against the substrate and the bolt thread hard against the nut or substrate thread, creating more friction and resistance to rotation. Applicable standards are ASME B18.21.1, DIN 127 B, and United States Military Standard NASM 35338 (formerly MS 35338 and AN-935).[10] Spring washers are a left hand helix and allow the thread to be tightened in a right hand direction only, i.e. a clockwise direction. When a left hand turning motion is applied, the raised edge bites into the underside of the bolt or nut and the part that it is bolted to, thus resisting turning. Therefore, spring washers are ineffective on left hand threads and hardened surfaces[citation needed]. Also, they are not to be used in conjunction with a flat washer under the spring washer, as this isolates the spring washer from biting into the component that will resist turning. The use and effectiveness of spring lock washers has been debated, with some publications[11][who?] advising against their use on the grounds that, when tight, the washer is flat against the substrate and gives no more resistance to rotation than a normal washer at the same torque. A 1990 NASA manual states "In summary, a lockwasher of this type is useless for locking."[7][12] However, a spring washer will continue to hold the bolt against the substrate and maintain friction when loosened slightly, whereas a plain washer will not.[a] The benefit of spring lock washers lies in the trapezoidal shape of the washer. When compressed to loads near the proof strength of the bolt, it will twist and flatten. This reduces the spring rate of the bolted joint which allows it to maintain more force under the same vibration le

[dodge28]

Naimbitten thank you Your explanation is well taken.  I know one place a copper flat washer is used and that is on Continental Flat head. The bolt between #2 and 3 pistons. The head bolt passes through the water jacket.

There are flat washers with rubber inserts on the inside . I used it on the water jacket of my 28 DB. I think it is useful where ever there are droplets hanging on the head of bolts, like used on oil pans.