Stainless fasteners

[milotron]

Hey, i have noticed some rust marks around several of the bolts at the elevator hinges and some other locations. The parts catalog notes these as cad plated, but stainless is available.

Any reason that I can't have these changed to stainless to prevent this in the future?

Also, what is the lubrication requirements for these hinges? One of the most stained ones definitely has some movement in it.

 

Thanks!

[carusoam]

Control surface hardware?

Definitely want to get proper strength ratings, SS would be an improvement... as long as the ratings go with it...

Got any pics or part numbers/diagrams of the hardware in question?  We have some good resources at MS to put these in front of...

Best regards,

-a-

[milotron]

Part numbers are attached.

It looks like tensile strength is the same for cad and stainless. I was actually more concerned that the harder stainless would wear out the hinge blocks instead of the bolt.

I have TKS and fly in the rain regularly. I suspect there is not much lube in there, whatever it is supposed to be.

[carusoam]

See if @M20Doc has some input for SS hardware used for flight controls.... Corrosion concern and hardware...

Best regards,

-a-

[Guest]

There is some concern of galvanic corrosion with stainless steel in contact with aluminum.  Your hinge fittings are aluminum.  I would replace the hardware with fresh new parts then paint the hardware if there is a concern.

Clarence

[milotron]

1 hour ago, M20Doc said:

There is some concern of galvanic corrosion with stainless steel in contact with aluminum.  Your hinge fittings are aluminum.  I would replace the hardware with fresh new parts then paint the hardware if there is a concern.

Clarence

Thanks for the advice. I knew there would be a reason for the cad plated hardware.  

Much appreciated @M20Doc  .

[PT20J]

I did some research on the bearings recently for another thread. They are PN3A needle bearings. They are not sealed and the Mooney maintenance manual calls for oil. 3-in-1 or similar will work. 

 

[Guest]

If you happen to have the flight controls off, you can attempt to re-greased them with one of these from Spruce.

Also if you have the elevators off, take note that Mooney often slipped thin #10 washers between the hinge fitting and the bearings.  These often go missing when unknowing maintainers remove flight controls.

Clarence

[Bartman]

How about a spray of TriFlow or LPS-2 every oil change ?

[Releew]

If you are going to switch from "Steel" to "Stainless Steel" there are a few things you need to do.....

• Re-tap with the appropriate thread size 8-32 on most (NOTE there is a slight difference between the diameter of the Steel and SS machine screw).  Failure to do this will increase your chances of binding the SS screw.  If you don't do this step you will understand what I mean on the next inspection!
• Use corrosion X to blow out the hole and coat with a lubricant
• Use plastic washers to eliminate galvanic action where the face of the machine screw can contact the aluminum sheet metal

Rick

[jaylw314]

2 hours ago, Releew said:

If you are going to switch from "Steel" to "Stainless Steel" there are a few things you need to do.....

• Re-tap with the appropriate thread size 8-32 on most (NOTE there is a slight difference between the diameter of the Steel and SS machine screw).  Failure to do this will increase your chances of binding the SS screw.  If you don't do this step you will understand what I mean on the next inspection!
• Use corrosion X to blow out the hole and coat with a lubricant
• Use plastic washers to eliminate galvanic action where the face of the machine screw can contact the aluminum sheet metal

Rick

I haven't heard this before?  Do you have a reference?

FWIW, I wouldn't use SS hardware on any aluminum structure or base just out of worries of dissimilar metal corrosion.  Fiberglass and plastic bases would be perfectly fine, though, and certainly use them in the cowling, for example.

[Releew]

Off the web...

The reason your stainless bolts are binding up is because of the composition of the steel. it is very strong due to the way the particles are arranged. when you tighten stainless steel bolts and nuts the stainless sometimes grabs and creates burrs inside the thread.

Note the receiver end (not plate) is steel, so by using a SS machine screws we are creating three metals.  I'll look for a chart on the shaft diameters but I can tell you from experience if you do not tap the holes the SS screws will gall and bind.  SS replacement screws kits for aircraft have been available for years.  

Try running a 8-32 SS screw in a steel nut plate and remove the screw instantly.  Feel the heat....  Now tap it and do the same test.  Really makes a difference...

I'm offering advice....not a mechanic.  I work with very good experienced licensed mechanics who turned me on to these tid bits.  I only offer up what I've proven myself.

Rick

 

[jetdriven]

If you tap the nuplate then it loses the locking function. 

[Releew]

OK..... I can only provide feedback to what I validated myself.  

[MB65E]

That’s because the stainless galls. Unless you use the nice structural stainless ones. Normal an526c screws are pretty weak. I kinda like the an525 screws myself. Not as pretty, but a much better screw. 

-Matt

[thinwing]

As pointed out ,nutplates contain standard threading but are crimped at the end to resist the screw backing out.Also they are high carbon steel and harder than stainless.That heating you’ve noticed is simple friction after the screw end has entered the crimped region.

[jetdriven]

I use a lot of stainless screws but I am very careful tightening them down. You snap off a stainless steel screw and it is pure hell to drill out. 

[PT20J]

I like SS screws and use them on the belly inspection plates. When I remove a plate, I put the screws in a zip lock bag and tape it to the plate - saves a lot of time searching for missing screws. I spray a little WD-40 in the bag so the screws are lubed when I put everything back together. Never had a galling or corrosion problem and they come out next year with no hassle. 

Skip

[RLCarter]

Like @PT20J I have SS screws on all the inspection plates and other places and never had any issues other than the occasional rounding of the screw head, maybe 4 or 5 out of over 1000. Replaced all the cowl sheet metal screws on the 172 which constantly loosen up with SS machine screws and steel nut plates, no issue there either (3 yrs). I've heard SS bolts are equivalent to grade 5 steal bolts, not sure I would use SS for any structual 

[Guest]

7 hours ago, PT20J said:

I like SS screws and use them on the belly inspection plates. When I remove a plate, I put the screws in a zip lock bag and tape it to the plate - saves a lot of time searching for missing screws. I spray a little WD-40 in the bag so the screws are lubed when I put everything back together. Never had a galling or corrosion problem and they come out next year with no hassle. 

Skip

Where is José? He’d be so proud that you’re using WD40 for something other than neutralizing uric acid.

Clarence

[PT20J]

2 hours ago, M20Doc said:

Where is José? He’d be so proud that you’re using WD40 for something other than neutralizing uric acid.

Clarence

I’ve actually found 2 other uses for it. I spray it on circular saw blades when I store them to keep them from rusting and it removes adhesive residue.

[Andy95W]

It's also an excellent degreaser for the belly.

[bradp]

I use it as a cutting lubricant when drilling sheet metal in a pinch.