NAS1149 Rev 7 'Washer, Flat' YAYYYYYYY... Major revision... EUREKA!!!

[WKTaylor]

In the 1990s NAS1149 washer-spec replaced AN960 washer-spec [NFND]... but NAS1149 retained original ID/OD/T dimensions and simply added different materials and finishes over-time.

About 10 Years ago... I, and probably many others... sent messages to the AIA [‘NAS spec owners’] begging for revision to NAS1149 to incorporate suitable 1OS & 2OS IDs ... to facilitate field repairs with NASXXXX OS bolts and pins. Otherwise... we-in-the-field/depot-maintenance would continue to modify existing NAS1149 washers by drilling the IDs oversized+ to accommodate X & Y OS bolt/pin shanks.

NAS1149-Rev7 now incorporates X, Y and Z [OS-IDs], suitable for 1-OS [+0.016], 2OS [+0.032] and 3OS [+0.048] Bolts/Pins... starting at #9 [0.188 Nom ID] up-to-2.500 [2.515 Nom ID]. These over-sizes are added-to the ID listed on the Nom ID table to accommodate fillet radii. This change appears to apply [in theory] to all thicknesses, materials and finishes in the noted ID ranges.

I hope these parts get stocklisted ASAP... our [corporate designated] oversized ID washers drive me nuts....

We need to get the word-out and get common sizes of NAS1149 washers stocklisted in X and Y [at least] OS-IDs... and maybe a few Z's... for-real!

Next on the agenda... get the AIA/NAS to incorporate zinc-nickel alloy plating [+post plating chromate treatment] to the washer allowed finishes... to get away from cadmium all-together...



Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[edmeister]

Congrats on the Amendment ..
But the battle is hardly over ! ..
These O/S washers will not be available until some OEM/Distributor orders sufficient quantities to make production viable.
Encountered various bolts in the past with X,Y,Z designations that only exist on paper .. Good luck!
BTW .. there is are Boeing washers with BAC designations that have been specifically mfr for O/S pins .. Fool not to have noted the P/N when i had the opportunity .. Anybody know what the P/N are ??

 

[Sparweb]

It would be WKT who gets excited for oversize washers... wow, what a subject for us all to take for granted.

I have no idea what spec to call for an oversize washer, but I can guess where to look one up. Firstly, even if ASSIST won't have a NAS spec for download, it may be the easiest site to search for at least the title. If anything matches you can get a spec number and go from there to the actual holder.
Another strategy would be to look up some OEM repair designs that are likely to require oversize bolts. Presumably if the repair calls for an oversize bolt it will also call for an oversize washer to match. Even if that doesn't work, there is at least the chance you will find a repair that calls for an oversize bolt and DOESN'T oversize the washer to fit - which would be worth a giggle or two, at the very least. If you're very desperate to know, you could scroll through the repair scheme to the serial number of the aircraft that needed that repair. Then call up the owners and ask them "so, what did you do?" That's probably taking it too far, though.

Wil,
What are your thoughts on using an oversize (presumably +1/32") washer for an oversize bolt, instead of (what most of us normally do) the next 1/16" size up washer?
I concede that the contact surface between the bolt head and the washer is reduced because the washer is a bit too big. But there is still an annular area of contact all around the bolt head.

Please remember: we're not all rednecks!

http://www.sparweb.ca

 

[WKTaylor]

There are only [2] spec for OS ID washers I've found... and they have limitations... thus...

MS14226 WASHERS, FLAT, FOR OVERSIZE FASTENERS AND FASTENER SLEEVES [MF 321,347 Annealed CRES sheet or 2024-T3 Clad aluminum sheet] [hasn't been updated since 1984]

MS27183 WASHER, FLAT (ROUND, STEEL, CADMIUM PLATED) GENERAL PURPOSE [MF Carbon steel sheet 'any temper', cd plated] [not for new design]

Anybody know of any others that are procurable and have published spec-data???

NAS1149 washers are sized for shear/shear-tension bolts and pins... that have relatively small fillet radii between the head and shank... so the ID is sized to barely clear bolt fillet radii. This 'sizing' remained true-to-purpose for the 1OS/2OS ID washer series... and provide optimum contact under the bolt head [which doesn't change as shank Dia is enlarged 1/64 or 2/64]. For this reason the washer OD doesn't change.

From experience, I have used 1/64 OS-ID [counter-bore] HL-collars for nominal or 1OS Dia bolts or HL-pins... due to simpler logistics... and because that combo was tested/approved [see most HL specs]. I tend to rarely use OS-ID washers for any nominal diameter bolts... because they are hard to find and needed elsewhere.. and have a poor-fit on installation... and bigger-gap that needs to be filled with sealant to be leak/moisture resistant.

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[NortheastAero]

Wil,

We would investigate putting a stocking program in on these.

In your experience what do repair manuals generally call out for regarding an appropriate washer when using oversize bolts? The above two you listed or are the manuals usually vague in that department calling for the AN960/NAS1149 in standard use, but then not being clear when it comes to oversize repair bolts?

Asking to try to get an understanding of how we would push them if they're not called out in a repair manual since the spec is newer than the book. I'm sure there are plenty of applications where it's fend for yourself in the field, but I would think the lions share of the potential of the oversize market is generally pretty well controlled with the book being God.

Maybe I'm overthinking it from a stocking perspective?

Frank Juarez

http://www.northeastaero.com