washer selection
washer selection
(OP)
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.
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.





RE: washer selection
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
RE: washer selection
rmw
RE: washer selection
RE: washer selection
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.
RE: washer selection
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
RE: washer selection
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!
RE: washer selection
Flat washers should be used under both the head of the bolt and under the nut.
RE: washer selection
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).
RE: washer selection
RE: washer selection
RE: washer selection
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.
RE: washer selection
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".
RE: washer selection
Larry
RE: washer selection
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?
RE: washer selection
Larry
RE: washer selection
htt
only specifies min and max thickness. Any chamfering that falls within the spec range would presumably be compliant.
TTFN
RE: washer selection
RE: washer selection
Larry
RE: washer selection
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
RE: washer selection
Larry
RE: washer selection
http://ww
RE: washer selection
RE: washer selection
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
RE: washer selection
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.
RE: washer selection
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 :)
RE: washer selection
I agree with you, its just a good idea. It may have no engineering basis but makes sense.
Nick
I love materials science!
RE: washer selection
RE: washer selection
Larry
RE: washer selection
RE: washer selection
It is a three axis HDR (High Data Rate) Submarine Satcom Antenna.
Larry
RE: washer selection
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
RE: washer selection
Nick
I love materials science!
RE: washer selection
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
RE: washer selection
RE: washer selection
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
RE: washer selection
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.