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  #11  
Old 09-29-2022, 09:15 PM
Walt's Avatar
Walt Walt is offline
 
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Stainless is soft, I only use when needed for cosmetic reasons
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  #12  
Old 09-29-2022, 09:51 PM
rocketman1988 rocketman1988 is offline
 
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Location: Sunman, IN
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Default Not All

Quote:
Originally Posted by Walt View Post
Stainless is soft, I only use when needed for cosmetic reasons
No, SOME Stainless is soft. There are alloys that approach or exceed the strength of the carbon steel used for AN507 screws.
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  #13  
Old 09-29-2022, 10:23 PM
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Quote:
Originally Posted by rocketman1988 View Post
No, SOME Stainless is soft. There are alloys that approach or exceed the strength of the carbon steel used for AN507 screws.
You have a PN handy?
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags, MTV-9 prop
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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  #14  
Old 09-29-2022, 10:34 PM
dmn056 dmn056 is offline
 
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ASTM A286 is a fairly widely used spec, 105ksi from my very fallible memory. Most of the usual fastener suppliers have them.
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  #15  
Old 09-29-2022, 10:49 PM
PilotjohnS PilotjohnS is offline
 
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Location: Southwest, USA
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Default do not recommend stainless

I thought I would be smart and use stainless screws firewall forward. That was a mistake.
Stainless screws have a nasty habit of seizing up. I am told it has to do with the way the screws are cut. Just out of A&P school, I got a job working on rocket stuff that used hydrazine fuel. We had stainless steel housing with cut threads and stainless steel screws. Every few months when we disassemble a part and we would get a screw seized in the housing.
On my firewall forward stuff, I had an Adel clamp screw seize. I had to cut the clamp. Then I remembered my past experience.

I do have a few stainless steel button heads in the cockpit that go into nutplates, These are for the tunnel covers where a allen head would rub against the passengers feet. Every where else they are now banned and get changed when I have to unscrew them.
YMMV
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  #16  
Old 09-30-2022, 04:17 AM
flysrv10 flysrv10 is offline
 
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I sharpen the blades and flatten the tip of the screw driver on my polishing wheel and it seems to help a lot in addition to using the right size screw driver bit.
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  #17  
Old 09-30-2022, 08:46 AM
raabs raabs is offline
 
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Stainless will stretch under too much torque And the threads deform with the stretch which is what makes it seize up. We have the same experience with Stainless bolts up to a quarter inch - it will seize from stretching and we have to cut them off. This is on non-aviation applications.

Low torque applications work OK but there’s a fine line when you hit too much torque.
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  #18  
Old 09-30-2022, 09:29 AM
David Paule David Paule is offline
 
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A286 stainless at 160 ksi is a very good material - hard to find and not cheap.

Here's a good hardware reference that you can download. It's free and shows what the hardware looks like and enough information to order it. But for a full description of the individual hardware, download the specification and look for it. Often a letter in the spec number can make a huge difference. I like everyspec.com for specifications when it shows up on a search.

Here is the spec for NAS517 flush screws. These aren't A286 but they are 160 ksi and will stand up to some abuse.

Click image for larger version

Name:	NAS517 Flush Screw.pdf
Views:	98
Size:	156.9 KB
ID:	31672

Aircraft Spruce has these at reasonable prices.

Dave
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  #19  
Old 09-30-2022, 09:30 AM
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Low Pass Low Pass is offline
 
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Location: Texas
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Been using stainless Torx now for ~20 years on access covers, fairings, tank skin/wing, wingtips/wing skin attachments, etc. The heads will strip, but only if you don't fully engage the bit. But nothing nearly as sensitive as the Phillips. Make sure the nutplate threads are loose and free. They will gall. If it's more than finger tight, run a tap though it once and all will be good.
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Last edited by Low Pass : 09-30-2022 at 09:32 AM.
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  #20  
Old 09-30-2022, 09:35 AM
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Walt Walt is offline
 
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Quote:
Originally Posted by Low Pass View Post
Make sure the nutplate threads are loose and free. They will gall. If it's more than finger tight, run a tap though it once and all will be good.
Hmmm...That pretty much negates the vibration resistant (locking) feature of the nutplate.
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags, MTV-9 prop
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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