What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Guide to Interpreting MS and NAS screws

blueflyer

blueflyer

Well Known Member
Can anyone point me to a table that will decode the MS and NAS screw descriptions? In this particular case, I am looking for a structural #6 machine screw, 1.5 inches in length, with a 100 degree countersunk head. For example, what does this mean: MS24694C10?
 
blueflyer said:
Can anyone point me to a table that will decode the MS and NAS screw descriptions? In this particular case, I am looking for a structural #6 machine screw, 1.5 inches in length, with a 100 degree countersunk head. For example, what does this mean: MS24694C10?
Click to expand...
corrosion resistant steel, length: 27/32", grip: 13/32", thread: 8-32, countersunk, flat head, machine screw, structural

I go to Aircraft Spruce and look at the catalog
#6 machine screw (#6 only in non structural screws) 1.5 long is a MS24693S36 in CAD plated Steel, or a MS24693C36 in stainless steel.
 
Aircraft Spruce is a good source to decode the various AN/MS part numbers. Their online or printed catalog is a great reference.

Another good one I have used is Genuine Aircraft Hardware Company:

Genuine Aircraft Hardware Co.

Genuine Aircraft Hardware stocks new traceable aircraft fasteners.
www.gen-aircraft-hardware.com

In addition to all the usual items, they carry some of the less common hardware. Best of all, they publish an AN/MS hardware reference book...well worth the $8 (with an order). Find it in the online catalog / Literature/Manuals / Tech Info icon. Or, just click here: https://www.gen-aircraft-hardware.com/amelia/details.asp?store=&id=106&TName_HID=maincat
 
plehrke said:
corrosion resistant steel, length: 27/32", grip: 13/32", thread: 8-32, countersunk, flat head, machine screw, structural

I go to Aircraft Spruce and look at the catalog
#6 machine screw (#6 only in non structural screws) 1.5 long is a MS24693S36 in CAD plated Steel, or a MS24693C36 in stainless steel.
Click to expand...
I think you are saying MS24694C10 = 27/32 length, 13/32 grip, 8-32 thread, countersunk, flat head, machine screw structural.
How does one interprets that from reading MS24694C10.

Bob-thanks for the confirmation about the #6 non-structural screw....I couldn't find a structural #6 either...
 
If you identify the mil spec you want info on, you can do a google search. Everyspec.com has them for free. NAS specs are harder to get.
 
If you're military the 1-1A-8 is usually easy to get your hands on and it's got the most comprehensive breakdown of bolts, screws, and other hardware you can imagine.
 
Do yourself (and everyone who works on the plane after you) and no NOT use stainless screws on your RV. The best ones are Cadmium plated steel screws. The corrosion resistant (stainless) screws are more brittle (the heads strip out) they tend to seize in the nut plates, they often then snap off in the nut plate, and stainless touching aluminum causes corrosion on the aluminum. It’s a lose/lose situation, they are also more expensive! Cad plating acts like a lubricant in the nut plate, and if corrosion wants to start, it’ll manifest itself on the Cad plating and not on the aluminum. Then you throw away and use new screws. (The cad plating is sacraficial)
 
GAHC used to have a neat little book covering many specifics of the hardware, its super handy. Not sure if they still make it but I know they pop into the forums now and again and maybe can chime in.
 
Taltruda said:
Do yourself (and everyone who works on the plane after you) and no NOT use stainless screws on your RV. The best ones are Cadmium plated steel screws. The corrosion resistant (stainless) screws are more brittle (the heads strip out) they tend to seize in the nut plates, they often then snap off in the nut plate,
Click to expand...
If you just simply must use stainless, a dab of beeswax on the threads will prevent galling in the plate nuts. Works for cad plated also.
 
Genuine Aircraft Hardware Co. www.genhardware.com also known as GAHco makes a really nice desk reference. I use it regularly.

I had not seen the 1-1A-8 document before. It is quite comprehensive!
 
The Aviation Mechanic Handbook is a great reference and is tool box sized for hardware reference.
 
OKAV8r said:
Thanks, I'll admit I'm not tech-savvy enough to understand it, but about 200 files were PDFs 10 minutes before I downloaded this one, and now they are all showing as HTMLs with broken links. Oh well...
Click to expand...
Sites uploading a document with a distribution outside government channels prohibited notice on page 1 don't tend to be the most trustworthy. Same kind of thing the War Thunder forums kept getting in trouble for.
 
Taltruda said:
Do yourself (and everyone who works on the plane after you) and no NOT use stainless screws on your RV. The best ones are Cadmium plated steel screws. The corrosion resistant (stainless) screws are more brittle (the heads strip out) they tend to seize in the nut plates, they often then snap off in the nut plate, and stainless touching aluminum causes corrosion on the aluminum. It’s a lose/lose situation, they are also more expensive! Cad plating acts like a lubricant in the nut plate, and if corrosion wants to start, it’ll manifest itself on the Cad plating and not on the aluminum. Then you throw away and use new screws. (The cad plating is sacraficial)
Click to expand...
Yah know, I've been watching an A&P friend do an annual and repairs on a Skyhawk. Everywhere a skin is secured by a SS Screw the screw head is surrounded by bubbling paint and corrosion. He is removing the parts to treat the corrosion and touchup the paint. Obviously he is not a fan and strongly recommends cad-plated screws for securing aluminum.
 
DaveWelch said:
Yah know, I've been watching an A&P friend do an annual and repairs on a Skyhawk. Everywhere a skin is secured by a SS Screw the screw head is surrounded by bubbling paint and corrosion. He is removing the parts to treat the corrosion and touchup the paint. Obviously he is not a fan and strongly recommends cad-plated screws for securing aluminum.
Click to expand...
Yup… bingo! Some people think SS is an upgrade.. I don’t!
 
DaveWelch said:
Yah know, I've been watching an A&P friend do an annual and repairs on a Skyhawk. Everywhere a skin is secured by a SS Screw the screw head is surrounded by bubbling paint and corrosion. He is removing the parts to treat the corrosion and touchup the paint. Obviously he is not a fan and strongly recommends cad-plated screws for securing aluminum.
Click to expand...
Just make sure to replace those cad plates screws after use. Once the thin cad layer is scratched the underlying steel fastener will start the corrosion process.

As for the bubbling paint, that can also be caused by poor surface prep prior to paint.
 
Taltruda said:
Do yourself (and everyone who works on the plane after you) and no NOT use stainless screws on your RV. The best ones are Cadmium plated steel screws. The corrosion resistant (stainless) screws are more brittle (the heads strip out) they tend to seize in the nut plates, they often then snap off in the nut plate, and stainless touching aluminum causes corrosion on the aluminum. It’s a lose/lose situation, they are also more expensive! Cad plating acts like a lubricant in the nut plate, and if corrosion wants to start, it’ll manifest itself on the Cad plating and not on the aluminum. Then you throw away and use new screws. (The cad plating is sacraficial)
Click to expand...
DaveWelch said:
Yah know, I've been watching an A&P friend do an annual and repairs on a Skyhawk. Everywhere a skin is secured by a SS Screw the screw head is surrounded by bubbling paint and corrosion. He is removing the parts to treat the corrosion and touchup the paint. Obviously he is not a fan and strongly recommends cad-plated screws for securing aluminum.
Click to expand...
rocketman1988 said:
Just make sure to replace those cad plates screws after use. Once the thin cad layer is scratched the underlying steel fastener will start the corrosion process.

As for the bubbling paint, that can also be caused by poor surface prep prior to paint.
Click to expand...

This is a bit of a "pick your poison" scenario. There is no universal best way or there would be no discussion.

SS screws were the answer to not having screws corrosively fuse to steel tinnerman nuts/nutplates and subsequently have their heads strip; but, SS causes galvanic corrosion to aluminum. Bees wax (as someone has mentioned) or Boelube paste on the screw threads helps the steel apps. If stainless hardware is necessary, nylon washers under the SS heads also goes a long way. Never a stuck panel screw after applying this approach and there were hundreds of access screws on them

Anybody remember Candlepower? They used to make were super thin and protected the paint/aluminum. Anyway, pick your poison then mitigate as needed.
 
Ive found you can’t interpret anything from a MS part number. Sometimes it feels like they just made the shortest one -1 and counted up from there.

I pretty much always have to refer to a table.

This is the most concise catalogue I’ve used - I have a printed copy which makes it even easier to wade through. It cross references the AN part numbers too.

Hardware Catalogue - AAE eStore

www.aaestore.com.au www.aaestore.com.au
 
You must log in or register to reply here.
Back
Top