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-   -   Self locking nutplate question (https://vansairforce.net/community/showthread.php?t=115843)

az_gila 07-30-2014 12:24 PM

Quote:

Originally Posted by bhassel (Post 902383)
Try Boelube if it's really tight to get the screw into the nutplate.

Bob

That's a good technique every time for the first use of a screw into a new nutplate.

rzbill 07-30-2014 07:44 PM

Washer stacks work and I used that technique sometimes but I also had a supply of 1/4 inch long phillips head #8 screws. I preferred them over the washer stacks.

BobTurner 07-30-2014 08:19 PM

Quote:

Originally Posted by rzbill (Post 902517)
Washer stacks work and I used that technique sometimes but I also had a supply of 1/4 inch long phillips head #8 screws. I preferred them over the washer stacks.

This is okay but you should paint all the heads orange so you don't leave them there by mistake. Otoh a stack of washers is hard to miss.

Toobuilder 07-30-2014 08:53 PM

Quote:

Originally Posted by az_gila (Post 902357)
The prevailing torque is the only requirement I found in several Mil Specs I checked. I could find no use limit numbers...

It is a material specification. Just as the surface finish, hole diameter, material, rivet hole dimension, etc.

The product must "meet or exceed" X cycles and retain run on torque....

Similar to the TBO on a Lycoming, if you can get more out of it, that's great!

BillL 07-30-2014 09:18 PM

By accident I found that the nut plate AND the screw wear in with cycles. I noticed that the hardware store stainless #6, #8 screws wear in pretty quickly. Then using a proper aviation screw the install friction torque jumps significantly.

You might experiment with this to get a better feel for it.

az_gila 07-30-2014 10:44 PM

Quote:

Originally Posted by Toobuilder (Post 902538)
It is a material specification. Just as the surface finish, hole diameter, material, rivet hole dimension, etc.

The product must "meet or exceed" X cycles and retain run on torque....

Similar to the TBO on a Lycoming, if you can get more out of it, that's great!

The older MS21047 specs do not seem to have any usage requirements -

http://www.everyspec.com/MS-Specs/MS...47F.034285.pdf

Did they add them when they became SAE specs?

Or are you referring to later, fancier, more expensive nutplates than we typically use?

The MS21047 -

http://aircraftfast.com/thumb.php?im...IF&w=300&h=300

rzbill 07-31-2014 04:28 AM

Quote:

Originally Posted by BobTurner (Post 902528)
This is okay but you should paint all the heads orange so you don't leave them there by mistake. Otoh a stack of washers is hard to miss.

Thats true. In my case they were commercial grade. Not sure what finish (possibly black oxide) but they were easily different than cad plated screws.

jarhead 07-31-2014 08:21 PM

I've never seen any reference to nutplate replacement after x cycles, in 20 years of both .civ and .mil helicopter maintenance, on multiple models from every "major" helicopter OEM (except the Russian OEMs). Plenty of references to loss of run-on torque, prevailing torque, and locking ability... but never "replace nutplates after x remove/install cycles".

Nutplates are an "on-condition" item, just like common panel hardware.

paul mosher 07-31-2014 08:31 PM

fiber
 
I think they are confusing fiber lock nuts with metal nutplates.

Toobuilder 08-01-2014 09:26 AM

Yes, they are "on condition"...

Yes, there is a material specification that states the nut plate must meet or exceed xx cycles. Don't confuse this "minimum specification" with a "recommended replacement schedule". If they meet run on torque, they are serviceable.

...but the point remains they do wear out eventually. We replace them by the thousands in depot.


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