When to use Loctite

[ebeowulf17]

I just got my first RC vehicle (Axial F100) and within less than two weeks I had a screw fall out. It was the screw that holds the steering link to the servo horn, so it made for an interesting field repair and a cautious drive home!

I checked some fasteners before I drove it for the first time, but I don't remember if I checked them all, so perhaps this was loose from the factory, or maybe it just worked its way loose in a very short order. Is it normal for things to come loose so quickly?

When I go to install a replacement screw, should I use Loctite? More broadly, are there general rules for when you should or shouldn't use Loctite in RC crawlers?

I design and build commercial espresso machines, and we use a lot of Loctite, but only on metal. The few plastics we work with are all acrylic, and Loctite does amazingly nasty things to acrylic, so I've just gotten used to the idea that you never use Loctite near plastic... but I realize not all plastics are the same.

Any advice on Loctite dos and don'ts would be much appreciated. Thanks!

[Panther6834]

Simply rule to follow:
ALWAYS use Loctite (always blue, NEVER red) whenever you have a metal screw going into metal. NEVER use Loctite when dealing with metal into plastic. Note that NOT all nuts are all h metal. If the screw is going into an all-metal nut, use Loctite...and, if the screw is going into a locknut, sick as a Nylock nut, NEVER use Loctite.

~ More peace, love, laughter & kindness would make the world a MUCH better place

[meatmonkey]

You've got the right idea using threadlock on metal to metal connections, and not using it in plastic threads. These trucks see alot of stress/flex when in use, so it's not uncommon for hardware to slowly loosen. Occasionally torque checking (which is not the same as simply "tightening") your wheel nuts, shock and link bolts, driveshaft through pins, and all steering hardware will go a long way towards keeping your truck reliable.

[nightcrawler48]

As you are familiar with Loctite you may know about purple loctite. This is the blue loctite equivalent for fasteners smaller than 1/4" dia. I've been promoting this for a couple of years now and I haven't had any issues using it on the small fasteners we use on our RCs.

Don't know if anyone else does it this way but I put a buttonhead screw through from the back side of the servo horn and long enough to be able to use a narrow nylon locknut to hold the steering arm in place. Works well for me.

[ebeowulf17]

Originally Posted by Panther6834

Simply rule to follow:
ALWAYS use Loctite (always blue, NEVER red) whenever you have a metal screw going into metal. NEVER use Loctite when dealing with metal into plastic. Note that NOT all nuts are all h metal. If the screw is going into an all-metal nut, use Loctite...and, if the screw is going into a locknut, sick as a Nylock nut, NEVER use Loctite.

~ More peace, love, laughter & kindness would make the world a MUCH better place

Excellent! That's simple advice that makes perfect sense to me. I'm glad there's a logical pattern to this. Reading some other threads here somehow gave me the impression that people were advocating Loctite in plastic. In retrospect, I bet I just misunderstood them because they had metal parts in some spots where mine are plastic.

Originally Posted by meatmonkey

You've got the right idea using threadlock on metal to metal connections, and not using it in plastic threads. These trucks see alot of stress/flex when in use, so it's not uncommon for hardware to slowly loosen. Occasionally torque checking (which is not the same as simply "tightening") your wheel nuts, shock and link bolts, driveshaft through pins, and all steering hardware will go a long way towards keeping your truck reliable.

Thanks! Do you have any advice on proper torque checking? Are there tiny torque wrenches suitable for this scale of work? Are there good rule of thumb numbers to target? Or is torque checking at this scale a totally different process than what I'm familiar with on larger fasteners?

Originally Posted by nightcrawler48

As you are familiar with Loctite you may know about purple loctite. This is the blue loctite equivalent for fasteners smaller than 1/4" dia. I've been promoting this for a couple of years now and I haven't had any issues using it on the small fasteners we use on our RCs.

Don't know if anyone else does it this way but I put a buttonhead screw through from the back side of the servo horn and long enough to be able to use a narrow nylon locknut to hold the steering arm in place. Works well for me.

Thanks for the tips! I've vaguely heard of purple Loctite, but never used it. Sounds like it's perfect for this application. The locknut scheme for steering sounds good too - I'll have to take a look and see how that would fit in my rig. Thanks!

[HumboldtEF]

Originally Posted by ebeowulf17

Thanks! Do you have any advice on proper torque checking? Are there tiny torque wrenches suitable for this scale of work? Are there good rule of thumb numbers to target? Or is torque checking at this scale a totally different process than what I'm familiar with on larger fasteners?

There are no specs, these fasteners are so small you dont get the typical bolt stretch that occurs on large fasteners and you dont need or probably want to use a torque wrench. It would likely just break things.
Just snug it up on plastic and give another 1/2 turn or so. Just remember you dont need to kill it just snug it up.
If metal to metal you can go pretty tight just remember these are small fasteners so again you dont need to kill it.

Also worth noting when screwing into plastic alone having the screw nice and snug will act like a lock nut by compressing the plastic. Sometimes when passing a fastener through a plastic hole but going into metal I will forgo the loctite so I'm not melting the plasic it passes through and I count on compressing the plastic to do the "holding".

[ebeowulf17]

Originally Posted by HumboldtEF

There are no specs, these fasteners are so small you dont get the typical bolt stretch that occurs on large fasteners and you dont need or probably want to use a torque wrench. It would likely just break things.
Just snug it up on plastic and give another 1/2 turn or so. Just remember you dont need to kill it just snug it up.
If metal to metal you can go pretty tight just remember these are small fasteners so again you dont need to kill it.

Also worth noting when screwing into plastic alone having the screw nice and snug will act like a lock nut by compressing the plastic. Sometimes when passing a fastener through a plastic hole but going into metal I will forgo the loctite so I'm not melting the plasic it passes through and I count on compressing the plastic to do the "holding".

Excellent! I feel like I'm learning a lot very quickly in this forum. Thanks for your help!

[Timmahh]

Torque spect? Make it snug, turn it a bit more till its tight. Leave it be.

Locktite will soften Plastic. It has a slight chemical reaction and over the span of a week or 3, the plastic will soften and the screws will be loose.

That is the main reason we don't use locktite in plastics. Also a reason why we clean any surfaces that have excess locktite on them, as even on the surface of a plastic piece like a Rod End where you may locktite the screw into the link ends, you want to keep it clean where it meets the plastic rod end, or it can soften the rod end, leading to a failure of the screw being pulled out of the now soft plastic end.


Never, Ever, Never, use a Stainless Steel Screw in an Aluminum Part. Trust me. The Stainless Screw threads will gnaw the Aluminum treads and that will cause them to bind up, making it very hard to remove without damaging the aluminum piece with needing at least new threads and a bigger bolt for them.

So locktite any OTHER Metal to metal connection, but because you will never put a Stainless Steel Bolt into an Aluminum piece, there is no need to locktite them. heh


But as far as "Torque Spects, if its in Plastic, if its Tight with finger strength, its probably tight enough. If I am tightening a bolt into aluminum, I make it finger tight, then give it JUST an Smidge more. With the locktite, it wont come loose so long as you allow the locktite to cure.

Only time you may want to use RED is in High Heat Situations. IE something that is metal with a bolt and is in the 225*f or hotter range. Ie Exhaust bolts on Nitros and 1/5 scale assets. Nothing we use gets that hot unless a lipo goes critical, so there shouldn't really be a need for red.

Keep the excess locktite cleaned up and not on the plastic parts or threads, and don't Over tighten. If if feels finger (not weak fingers) tight, it is tight enough.

Always good to go over the rig every 2 or 3 runs checking bearings, bolts etc anyways. And that gives a time to maintain, clean, and hopefully not find any gremlins.

[TRX4ME]

Will just add, use sparingly! Most use too much - more does not hold better. Just a light coat on the threads - should not drip off the screw.

[Timmahh]

Originally Posted by TRX4ME

Just a light coat on the threads - should not drip off the screw.

Easier said than done. lol

[Panther6834]

Originally Posted by Timmahh

Easier said than done. lol

Actually, very easy to do. Start by squeezing a few drops onto a piece of plastic (never paper...it will absorb the Loctite). Then, for each screw needing Loctite, I place the screw onto the hex driver, hold it in place with a finger (or nail) from the other hand, and then lightly 'dip' the lower edge of the screw into the Loctite...perfect amount (almost) every time. The only real exception would be the really tiny M2 & M2.5 screws...but, with practice, even those become easier.

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[high plains drifter]

Few tips not sure if mentioned-

> Use a toothpick, a Q-tip, or a folded square of toilet paper to keep things from getting messy. Sometimes locktite wants to seep out of the tube before, during, or after use. Don't squeeze the tube too hard. I just shake it a little to get the fluid to the tip. If too much comes out, just wipe it up before it drips everywhere.

> Also if you're worried about using too much on a certain screw, then you can just drip the locktite onto a toothpick or paperclip. Then touch that to the screw or even into the hole that the screw is going to go into.

> Some precision jobs are much easier ( especially with really small screws or with screws that are going into hard to access areas) if you first put the screw onto the tip of the hex-driver.. then [gently] apply the locktite to the screw. This way your fingers never touch the threads and everything stays clean.

*** If you ever apply too much loctite, just briefly/ delicately touch a Q-tip to the screw to wick away the excess. With a little practice you can easily control exactly how much loctite you want on the screw. And always always... SHAKE WELL before use.

[Khofman]

Originally Posted by Timmahh

Never, Ever, Never, use a Stainless Steel Screw in an Aluminum Part. Trust me. The Stainless Screw threads will gnaw the Aluminum treads and that will cause them to bind up, making it very hard to remove without damaging the aluminum piece with needing at least new threads and a bigger bolt for them.

So locktite any OTHER Metal to metal connection, but because you will never put a Stainless Steel Bolt into an Aluminum piece, there is no need to locktite them. heh

Wasn’t aware of this - I just ordered a Team KNK stainless steel screw kit from my Yeti Score. There’s a bunch of aluminum upgrades (VP, SSD, etc) so should I keep stock steel hardware in stuff like the VP yeti aluminum front gearbox?


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[durok]

Speaking of Loctite dripping from screws...

I ordered this for my next build:

"Loctite 506166 All-Purpose Medium Strength Anaerobic Threadlocker Stick, Blue, 9-Gram"

Perfect for use on smaller screws, it's a waxy Chapstick-like product. Just touch the end of your screws and bolts to it and then thread them in.

[Khofman]

Wow never seen that thread locker stick before! Definitely ordering some ASAP


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[Benp]

Originally Posted by durok

Speaking of Loctite dripping from screws...

I ordered this for my next build:

"Loctite 506166 All-Purpose Medium Strength Anaerobic Threadlocker Stick, Blue, 9-Gram"

Perfect for use on smaller screws, it's a waxy Chapstick-like product. Just touch the end of your screws and bolts to it and then thread them in.

Thank you Durok!

Just ordered some

ETA - apparently I live under a rock. I just asked my coworker if he was aware of this. He said he’s been using it for a little while.

[durok]

Yeah, I've always hated the tiny bottles of the fluid, so hard to get it out in the proper amount, and always wasting some of it...

This stuff is MUCH better!

[Panther6834]

Thank for the stick info...gonna have to order some.


~ More peace, love, laughter, & kindness would make the world a MUCH better place

[Panther6834]

Originally Posted by Timmahh

The other never do, is never use Stainless Steel in Aluminum pieces, and NEVER Locktite it if you do.

The Stainless gnalls Aluminum and either locks the stainless into the aluminum breaking the bolt, or stripping the treads in the aluminum.

That's "interesting" considering many kits include SS screws. What about Ti screws into aluminum?



~ More peace, love, laughter, & kindness would make the world a MUCH better place

[Timmahh]

Originally Posted by Khofman

Wasn’t aware of this - I just ordered a Team KNK stainless steel screw kit from my Yeti Score. There’s a bunch of aluminum upgrades (VP, SSD, etc) so should I keep stock steel hardware in stuff like the VP yeti aluminum front gearbox?


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They may be great for 10 times. but the one time they lock up, 1st or 20th, is a mess to deal with.

Ask me how I know. lol