BruceMe

BruceMe

Well Known Member
We all know, love and swear at these good old -8 screws. Does anyone know of any better alternative? My RV-4 came with these crazy tri-wing screws. I used them and I kinda liked them, but they stripped just as easily (maybe easier). Has anyone tried Torx, hex or square head alternatives? What do you think? Are they structural (graded/certified) or non-structural (box store)?

Thanks,

-Bruce
 
Careful!

The AN509 screws are structural strength screws, 125,000 -- 145,000 psi material. They are used in specific locations where that strength is important (like the gas tank attachment screws, which carry a lot of shear).

The Microfastener 6-lobe screws are great for places where structural strength is not important, like holding wing root fairings on, removable floor panels, inspection panels. Typically these locations would use AN507. But I would not recommend deviating from the plans in a place where AN509 screws are called for.
 
Torx

ChiefPilot said:
These were recommended to me by a local builder but I found they galled, stripped, and even broke at a far greater rate than the AN509 screws. I ended up throwing them out and replacing them with AN hardware.
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I have not (yet) had any of those problems, and I only plan to use them in non-structural applications. It would be great to get some real AN/MS hardware with the torx head - I find torx much less likely to strip than phillips or even allen heads. I also would prefer if they were cad plated.
 
BruceMe said:
We all know, love and swear at these good old -8 screws. Does anyone know of any better alternative? My RV-4 came with these crazy tri-wing screws. I used them and I kinda liked them, but they stripped just as easily (maybe easier). Has anyone tried Torx, hex or square head alternatives? What do you think? Are they structural (graded/certified) or non-structural (box store)?

Thanks,

-Bruce
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Try GAHCo--They are a aviation hardware supplier and, I think, advertiser here. They've in the past offered AN/structural strength torx versions. They may even have some in stock. Usually they just need to know there is a demand. In any case, they are a great company to work with.
 
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As far as I could determine, the AN509 is the same as the MS24694 which superseded it. These are 125 ksi flat head screws.

You might try the NAS1202 screws for the #8 size, and NAS1203 for the #10 size. I couldn't find a spec on them but Aircraft Spruce carries them and advertises them as 160 ksi. That will make them stronger and the heads less likely to get messed up.

Dave
 
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