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.

 

[CESSNA1]

49078:

If you are using lock washers they should go above the flat washer and below the bolt head (or nut) Usually the wrenching surface (bolt head or nut) with the washer is held and the nut ot bolt head is tightened. The flat washer always goes against the surface to prevent damage by the lock washer.

Regards
Dave

 

[rmw]

The flat washer also spreads the clamping load.

rmw

 

[49078]

Should I ever need to use two flat washers? One on both sides for anything other than fixing possible spacing problems?

 

[pauljohn]

I have never had much luck with the spring loaded lock washer.

If the torque of the nut and bolt doesn't hold the fastener together, then how can the spring of the washer (which must be less than the torque of the bolt) do anything?

In my experience the nylock nut works better. I would be interested in hearing what anyone else thinks.

 

[mrMikee]

49078,

You only put a flat washer under the turning element, either the nut or the bolt head, depending on how it is being tightened. For some interesting discussions on split lockwashers try the following threads. There's some good advice there.

thread725-145968
thread108-114051

Regards,
-Mike

 

[intentsly]

I was wondering what the consensus is on whether or not washers that have a rounded and a flat side should always be put on the flat side down to the mating surface?
I'm trying to convince some co-workers that the above is a good idea and therefore increase consistency and reliability in our assemblies.
Some say that there is no difference and that its just a piece of metal. I feel that there is more surface area in contact with the mating surface with the flat side down and therefore a stronger connection.
Thank you!

 

[MintJulep]

Don't use split lock washers, they don't do anything.

Flat washers should be used under both the head of the bolt and under the nut.

 

[greatleo]

Spring Lockwashers become flat and have NO grip when the hardware is properly torqued. I agree with people who say they are somewhat worthless in keeping a nut or screw from "coming loose". My opinion is that they may (may) help the nut from falling off after it becomes loose, but I don't like them all-in-all. Proper torque is your answer for assemblies to stay together.

Flat washers always, and on both sides, if bolting thru "slots" as opposed to holes.

Many other types of lockwashers (other than one-split spring-type) are available and do work on small screws. People who have said "place the lockwasher next to the nut or bolt-head" have my agreement (if you must use them due to Assemblers not willing to do it differently, or bosses who require them).

 

[greatleo]

Oh yeah...to respond to intentsly: The cross sectional shape of the flat washer is more likely a result of the way it's manufactured not design-intent. I don't believe it makes any difference which side is up. Think about using a fender washer if you want to cover more surface under the screw-head.

 

[greatleo]

intentsly: Flatwasher really doesn't matter which side is down (except maybe appearance). If you want more contact-area use a larger washer. I don't think the shape of the washer is a design-intent, but a result of fabricating the washer itself.

 

[diamondjim]

intentsly,
The rounded side goes toward the bolt
head to help assure clearance at the
elliptical radii on the bolt under
the head. So you are right in that
the flat side is designed to go
on the structure side. Some washers
have a chamfer instead of a radius
on the id of the washer for the same
purpose and only on one side.

 

[MintJulep]

ASME B18.22.1 "Plain Washers" does not discuss flatness or a radius or chamfer on the ID. The dimensional tables and associated illustrations do not show a radius or chamfer.

ASTM F844 "Unhardened Steel Washers" allows (not requires) washers to be out of flat within limits, and perscribes a method of measurement. It refers back to B18.22.1 for dimensions.

ASTM F436 "Hardened Steel Washers" allows (not requires) washers to be out of flat within limits, but does not perscribes a method of measurement. There is no radius or chamfer indicated in the dimensional tables and figures.

From this I conclude that washers manufactured to any of these standards are not intended to be "sided".

 

[intentsly]

Thank you for your replies. I do understand that the washers we use are manufactured by stamping causing a rounded side and we have no choice in the type we use, as we are building to a customer's drawing specification (gov't work ). I think that the round shape would work better on the bolt side mating surface as our bolts tend to have a radius where the washer's id would mate. I'll put your replies into the ears of my coworkers. Thank you!

Larry

 

[MintJulep]

I would love to overhear the conversation between the assembly technicians and the engineer where the engineer explains that the orientation of every freakin flat washer needs to be ascertained so that the washers can be installed in the correct orientation.

I would also love to be there when the government inspector comes in, reads the process instruction explaining washer orientation, and starts checking for correct orientation and starts rejecting stuff for incorrect washer orientation.

Do you people ever get out on the shop floor?

 

[intentsly]

I do assembly on the floor and find that work ethics are always at different levels. This seems to correspond to certain age groups as well. Being ex-Navy myself, I seem to feel a bit more responsible for the quality of the assemblies that are being made, since they are deployed on military crafts. So, its not so much a question of it being a requirement, but a feeling of doing the right thing. If all washers are put on in the same orientation at all times, then how could the assembly not be consistent time after time? A sense of team spirit/comaraderie goes a long way as well, and if it can enhance the quality of the assemblies I will keep pushing in that direction. Thank you!

Larry

 

[IRstuff]

MS16212B WASHERS, FLAT, METAL, ROUND, MEDIUM SERIES, NONMAGNETIC:

http://assistdocs.com/search/docume...tle=WASHERS&status_all=ON&search_method=BASIC

only specifies min and max thickness. Any chamfering that falls within the spec range would presumably be compliant.

TTFN

 

[ewh]

Is the clearance so tight that this is necessary? Or is this another $300.00 hammer situation?

 

[intentsly]

In my case, its not a requirement to put a washer on one side or the other specifically. I'm just trying to get ammo for my opinion and see if I can get the reluctant/non-caring to consider doing the assemblies all the same way. Cohesion is the goal, not just the occasional adhesion. Thank you.

Larry

 

[MikeHalloran]

The clearance between the bolt shank and the washer i.d. allows room for the fillet under the bolt head. Even if that were not true, bolt heads are hard relative to flat washers, and can easily form the washer to a shape complementary to their own fillet. Hardened washers are an obvious exception, and are nearly always chamfered on the i.d. for obvious reasons.

In my own personal work, where assembly time is not an issue, I prefer to put the radiused face of the washer under the bolt head, not because of anything to do with the bolt, but because the o.d. of the washer is usually radiused on the same face, and a washer installed with the radiused face out is less likely to slice flesh that comes into accidental contact with it.

Similarly fussy individuals might wish to install washers the exact opposite way, so as to not cut through whatever paint film or wood lies under the washer.

Really fussy individuals just buy better washers with less of a die break burr.



Mike Halloran
Pembroke Pines, FL, USA