Fatal - AutoGyro MTOSport D-MTMZ, near Hildesheim airfield, Germany

Uncle Willie

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If you are reusing a Ny-Loc Nut and you can turn it with your fingers, it needs to be replaced.
If it needs to be wrenched on the whole way and feels like new, it is OK to be reused.
Use common sense.

Loctite 242 and its close cousins are Not recommended for use with "Plastics". Read the package.
It may be called a "Nylon" Locking Nut, but do you truly know what plastic really is used?

Loctite 425 is intended for use on Plastic parts. Not Cheap!!! ~$25 per half-ounce.
It is labeled as "Low Strength", But don't assume that means you won't need tools.
It is more like Super Glue Strength than Red Loctite Strength.
 

fara

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I read (or was told), Loctite is not good for Nyloc nuts - use either Loctite or use Nyloc nuts.

Was it wrong advice?

No. Not bad advice. You should only use it on deformed metal lock nuts (which also should not be used if they cannot hold prevailing torque) or on multi used nylock nuts if you cannot or somehow are not able to get new ones for the moment and they are not holding prevailing torque. Usually a nylock nut will hold minimum prevailing torque for 5 to 10 times of reuse.
At the end of the day Loctite or Permatex are anaerobic compounds with their base being saccharin. They will play havoc on thermoplastics. Nylon 66 should not be effected by them but if you are looking at metric nuts or SAE nuts (not something like AN365, 364 nylock nut), you probably don't have Nylon 66 alone lining the nut for locking. Most likely use Zytel resin inserts which is based on Nylon 66. Anyway, better to be safe.
 
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JETLAG03

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@fara Whilst I accept your comments re nyloc can be re-used on the same bolts, for the cost, I will continue to use only once.

thanks

phil
 

fara

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No. Not bad advice. You should only use it on deformed metal lock nuts (which also should not be used if they cannot hold prevailing torque) or on multi used nylock nuts if you cannot or somehow are not able to get new ones for the moment and they are not holding prevailing torque. Usually a nylock nut will hold minimum prevailing torque for 5 to 10 times of reuse.
At the end of the day Loctite or Permatex are anaerobic compounds with their base being saccharin. They will play havoc on thermoplastics. Nylon 66 should not be effected by them but if you are looking at metric nuts or SAE nuts (not something like AN365, 364 nylock nut), you probably don't have Nylon 66 alone lining the nut for locking. Most likely use Zytel resin inserts which is based on Nylon 66. Anyway, better to be safe.


Here is the official engineering advice on Loctite 242 from Loctite team

Question asked:
"Hi
I wanted to know if Loctite 242 will dissolve or make brittle nylon insert in a Nylock locking nut or not?
Thanks"

Answer by Loctite:

"Thank you for contacting us.

LOCTITE Threadlocker 242 is a medium strength threadlocking adhesive offering general
purpose qualities. The product provides quick fixture times on steel, brass and stainless steel
of 5, 15 and 20 minutes respectively.

Please refer the link for more product details and description :
https://www.tryloctite.in/estore/threadlockers-loctite-242-AD.TH.333219/

Hence the above Loctite Threadlocker 242 will not dissolve or brittle the nylon insert in the
nylock locking nut , it will simply secures and seals bolts, nuts and studs to prevent loosening
due to vibration."
 

Uncle Willie

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It doesn't look like the Loctite rep reads their own literature ...
- - -
Directly from the Loctite 242 FAQs ...

Can I use anaerobics where one or both parts are made of plastic?
Anaerobics are generally not recommended for use with plastics as they might result in stress cracking or softening.
In such cases, cyanoacrylates are recommended.
- - -

The Loctite 425 I mentioned earlier is a Cyanoacrylate Thread Locker for use on Plastics.
242 may be OK if the Locknut is truly Nylon and not something else.
The wise man would test for compatibility before committing the whole assembly.
 

fara

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It doesn't look like the Loctite rep reads their own literature ...
- - -
Directly from the Loctite 242 FAQs ...

Can I use anaerobics where one or both parts are made of plastic?
Anaerobics are generally not recommended for use with plastics as they might result in stress cracking or softening.
In such cases, cyanoacrylates are recommended.
- - -

The Loctite 425 I mentioned earlier is a Cyanoacrylate Thread Locker for use on Plastics.
242 may be OK if the Locknut is truly Nylon and not something else.
The wise man would test for compatibility before committing the whole assembly.


This wasn't a Loctite Rep. It was Loctite technical support from Henkel.
Plastics is a large wide thing. The stress cracks and brittleness would happen in certain thermoplastics like Plexiglass/acrylics, polycarbonate/lexan etc.
Nylon should be ok. If we are using cheap Chinese nuts, God help us because no telling what exactly was used. But generally good quality industrial nylock nuts (including those made to spec in China or Taiwan) and MS or AN nuts will use Nylon resin to make the locking mechanism. Easy enough test though to do
 
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