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Replacement screws-stainless or other?

R

RNB

Well Known Member
Patron
New to me RV, I think from the plans that the screws that hold things like access panels and wheel pants are stainless steel. I think I have read that these can strip easier, I see some evidence of this on mine. I am going through the plans, getting a list of screws by part numbers, seems like the easiest thing to do is order from Vans.

I'd come across a discussion about getting screws made of different materials, perhaps so they are not subject to this stripping while still not rusting.

What do most people do for this and why? If you advocate for a different product, which one?

If I order, it seems like searching a part number gives an equivalent part number in different terminology. I need to decipher the hidden meanings...

AN507C832R8
AN507C632R8
AN526C832R8
AN507-6R6
AN509-8R8


Thank you.
 
Personally, I have just stayed with stainless, and replace them when they start to look sketchy (which is not that often). I do use JIS bits to alleviate the stripping problem.

Before ordering replacements based on the plans, double check your builder did not go off schedule and use something different.
 
Vans specs their screws out way too long. The standard in the industry is 1-3 threads showing past the fastener.

I’m looking at replacing stainless with titanium.
 
RNB said:
New to me RV, I think from the plans that the screws that hold things like access panels and wheel pants are stainless steel. I think I have read that these can strip easier, I see some evidence of this on mine. I am going through the plans, getting a list of screws by part numbers, seems like the easiest thing to do is order from Vans.

I'd come across a discussion about getting screws made of different materials, perhaps so they are not subject to this stripping while still not rusting.

What do most people do for this and why? If you advocate for a different product, which one?

If I order, it seems like searching a part number gives an equivalent part number in different terminology. I need to decipher the hidden meanings...

AN507C832R8
AN507C632R8
AN526C832R8
AN507-6R6
AN509-8R8


Thank you.
Click to expand...
AN - Meets Army-Navy hardware specifications (milspec)
507 - non-structural screw, countersunk head - threads go all the way to the head
509 - structural screw, countersunk head - the top end of the shank is not threaded - makes it stronger to hold parts together
C - corrosion-resistant (stainless steel)
832 - size 8, 32 threads per inch
R - Phillips head
8 - length in 16ths of an inch (1/2”)

For the AN509, size 8 defaults to 32 threads per inch and it’s not specified in the model number.

If there is no C, then it defaults to cadmium-plated carbon steel.

That’s just a very minor intro. And then there’s the newer, current MS system (Military Standard). Download this catalog, which has cross references for all of the items with multiple designations.

 
I transitioned to stainless torx head screw for all of my #6 screws and have stuck to cad plated for all of the #8’s. i tend to use my drill to speed up the process and that’s an easy way to strip a #6 Philips. Torx reduces but does not eliminate the potential. If I feel any resistance I use a regular screwdriver but I have to save I’ve become quite adept at using screw removal tools over the years.
 
RDB: If you go to everyspec.com and select the Library tab, then select AN in the pulldown box and then select the range for the spec, you can pull up the entire spec and decode it within a short time. The spec will give you all the dimensions, grip lengths (if applicable), material type and finishes. IT will also tell you if the spec has been superseded or cancelled. Don't fret about cancellations, as it is always for new military designs after a specific date. Lots of good data can be found there and is worth getting familiar with it, how to find the spec and how to read the specs as well.
 
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Stay away from Stainless Steel Fasteners on aluminum if you live near a salt water environment. The screws will stay in good shape as your aluminum gets eaten away.
 
Auburntsts said:
I transitioned to stainless torx head screw for all of my #6 screws and have stuck to cad plated for all of the #8’s. i tend to use my drill to speed up the process and that’s an easy way to strip a #6 Philips. Torx reduces but does not eliminate the potential. If I feel any resistance I use a regular screwdriver but I have to save I’ve become quite adept at using screw removal tools over the years.
Click to expand...
What’s your source for #6 SS torx 100* screws?
 
Use nylon washers to prevent corrosion between the stainless steel and aluminum.

www.aircraftspruce.com

Nylon Washers | Aircraft Spruce

Nylon Washers Nylon Washers
www.aircraftspruce.com www.aircraftspruce.com

Cad and SS screws are also available at Spruce.

www.aircraftspruce.com

AN526 Machine Screws | Aircraft Spruce

AN526 Machine Screws Truss-head non-structural machine screws made of carbon steel, cadmium plated. Minimum tensile strength 55,000 PSI. Available in slot head or Phillips recessed head. Part Length...
www.aircraftspruce.com www.aircraftspruce.com
 
Last edited:
I changed all of these to AN stainless Steel screws at the time my plane was painted. This eliminates the need to constantly paint the heads of new screws to match the paint job. When installing, I always place a drop of Hoppe's #9 gun oil on the threads. It comes in a needle point applicator. Stops galling and allows slightly easier installation in the nutplate. I buy all of the screws by the 100 from Spruce and change then about every second or third time they are removed.

It is a bit more costly, but then again, so is the hobby of flying!
 
jmra72a said:
I changed all of these to AN stainless Steel screws at the time my plane was painted. This eliminates the need to constantly paint the heads of new screws to match the paint job. When installing, I always place a drop of Hoppe's #9 gun oil on the threads. It comes in a needle point applicator. Stops galling and allows slightly easier installation in the nutplate. I buy all of the screws by the 100 from Spruce and change then about every second or third time they are removed.

It is a bit more costly, but then again, so is the hobby of flying!
Click to expand...
I think that most of the wear and tear on the threaded fasteners comes from the screw being too damm long!

My aircraft builder followed the plans and the aircraft came with half inch long screws everyplace. That has about 6 threads showing on the other side of the fastener. Removing those extra threads causes extra heat and galling. Remove the extra threads and reduce the problem.

When my project came apart for transport, they said the same thing. They recommended all new fasteners. I’m going with titanium of the minimally acceptable length.

25+ years A&P mechanic
 
I've read through most of this, but I see no reference to the structural nature of a lot of these screws vs. the suitability of "random" stainless. It might be shiny, but it isn't the same.

I built, flew and maintained the RV9 for 15yrs with a few torx screws in various places that seemed like a good idea when I thought I knew better. I'm not doing that again. I always have the right size phillips at hand.
 
scard said:
I've read through most of this, but I see no reference to the structural nature of a lot of these screws vs. the suitability of "random" stainless. It might be shiny, but it isn't the same.
Click to expand...
SS is ok for fairings and stuff but as you noted it isn’t a structural fastener.
 
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