washer selection 2

[49078]

I'm wondering when should lock washers be used? Do they always have to be used with a flat washer? Does it matter what order they go in?

As well, in the past I had been using washers on the bolthead side of a connection. On this current project they are stating to always put them on the nut side of the connection. Does it matter?

I have no idea about any of the factors to determine when to use what and when. Any help would be appreciated.

 

[intentsly]

I agree also that the radiused side would prevent damaging other things that might come in contact with it, such as cabling/wire insulation etc.. This, in my case, is not so relevent due to the way they are made, but a good thought none the less! Nothing wrong with adding value to a product by making it safer for use

Larry

 

[bob1371]

About 10 years ago we recieved some machinery from Spain that had a locking washer I had not seen before. I have since used them almost daily without problems.

http://www.stanleyind.com/product/washer/nordlock/nord.html

 

[unclesyd]

There is an industry standard for a better quality flat washer. If you callout a "Finished Washer" in a particular size you can get much better quality product. There is a slight premium on small lots, but this differential diminishes quickly with quantities.

 

[Screwman]

Intense,
It will not matter one iota in how your assemblies perform how the flat washers are oriented. The differences caused by your use of "lockwashers" will far outweigh any influence from the orientation of the flat washers.
If you are using unhardened washers your loads must be relativley low so you won't see significant embement.

You need to worry about the level of hydrogen relief in those lockwashers if you want to assure good product for the troops. They are notorious for stress corrosion cracking. That is one of many reasons why I won't use them. Make absolutley sure that those lock washers have been baked way more than the minimum spec if you don't want to have broken washers all over the deck when they see salt water.

Dick

 

[greatleo]

I hope that "49078" is still reading this thread. There has been much more discussion on washers than was originally asked.
If we are now talking about "value added" and "quality", neither is a result of orienting a flat washer a certain way. If the Assembler must inspect and be aware, (and in worst case disassemble and reassemble) because someone wants a washer-radius out instead of in this does NOT add value to the mechanism/assembly. Functionally it is the same...appearance is negligible. Why beat this anymore? Just call for the components on the BOM and your job is done. If you want to use just a flat washer...call for it, if you want lock washer first then flat...say so, IF YOU WANT FOUR WASHERS STACKED UNDER THE NUT...OK! There are situations for any scenario. But, do you specify a torque on your assembly drawing? That's at least as important.
I like the nylon-lock nuts (ESNA) and flat washers. My opinion. Less problem with vibration-caused loosening, and they are readily available in plated or stainless.

 

[intentsly]

We don't have a say as to what goes on the BOM. I wish it were as simple as getting the parts we wanted or assembling something a different way. We build to print and don't have much say unless something is obviously causing a problem.
I think, if something is assembled the same way each time, that it does add value. Repeatability and attention to detail that goes into complex assemblies adds tons of value in not having to do rework.
Our assemblies are thermal tested and vibration tested as well. The thermals are brutal and vibe is no lightweight either. We also use larger washers where appearance tends to make all want them to go the same way. Why not just do it for all of them? End of Rant

 

[NickE]

"I think, if something is assembled the same way each time, that it does add value. Repeatability and attention to detail that goes into complex assemblies adds tons of value in not having to do rework."

I agree with you, its just a good idea. It may have no engineering basis but makes sense.

Nick
I love materials science!

 

[49078]

Well I never thought this would be such a popular thread. It was interesting to keep up with it.

 

[intentsly]

Thank you, for putting up with my additional question of washer orientation!

Larry

 

[NickE]

Larry- is that povray?

 

[intentsly]

NickE-
It is a three axis HDR (High Data Rate) Submarine Satcom Antenna.

Larry

 

[Tunalover]

IRStuff-
FYI MS16212 is inactive for new design. I use MS15795, NAS620, and AN960. These seem to offer everything I've ever needed except a reduced diameter washer for No. 1 screws.


Tunalover

 

[NickE]

larry- povray is a raytrace/rendering software, I thought the image might have been created using it. Thanks


Nick
I love materials science!

 

[intentsly]

NickE-
I thought thats what it was, lol, but just wasn't sure exactly what you meant. Its just a standard realtime pic in jpeg format. I think the cad/rendering software our company uses is solidworks.

Larry

 

[CVN78]

Tunalover, you might want to review SAE J2655. We on the SAE Ships Systems Technical Committee-Fasteners Subcommittee wrote it to replace the numerous Mil and Fed specs for washers. The Mil and Fed Specs are out of date. For example no one really manufactures to the dimensions for flat washers specified in Mil Standards unless they're ASME. J2655 gives us an up to date industry standard and will promote standardization and reduce costs. It's now been invoked for the new generation aircraft carrier being designed. I'm presently working on some minor updates for a new revision which we hope to publish by the end of the year.

 

[Tunalover]

CVN78-
Unless J2655 issues part numbers that are recognized by fastener distributors I'm afraid we can't buy to it. Even if the spec issues part numbers our buyers (not being very resourceful) would refuse to make multiple phone calls to find a source. What about that new ASME spec that has a part numbering system for most common US standard fasteners? I can't recall the number.


Tunalover

 

[CVN78]

Tunalover-
The great thing about J2655 is it's simplified PIN system. Five fields at most to fill out. ASME system horrible, it's too long and complicated. If you wanted Series 300 Cres (without the free-machining garbage) with J2655 you can put in one designator whereas with ASME you can only list one alloy which would you force you to list multiple PINs. RevCar Fasteners in Roanoke Va. who is our primary supplier is versed in J2655. They sell to the Navy and industry.