Safety Wire vs Loctite vs Castle Nut

[vhol5]

Can anyone explain the different uses, and pros and cons of each?

 

[ddawg16]

Long conversation.....

Safety wire....think aerospace, or any application where you can not take a chance of something coming loose.

Castle Nut - Used with a cotter pin....most common use is suspension components.

Loctite....cheap easy way to secure nuts and bolts

 

[jkeyser14]

Safety wire is used where a bolt loosening would be completely, 100% unacceptable. It also requires a pattern of bolts to tie the wire to, you can't have just a single bolt. It may also involve high temperature applications or many thermal cycles. Think nuclear missiles and reactors, or billion dollar space programs.


Castle nuts and cotter pins are used where failure is unacceptable and you cannot safety wire the bolt/nut to multiple other bolts or nuts, and weight isn't super critical. It os also used for high temperature applications that may have thermal cycling.

Loctite is used wherever a low cost solution is needed AND the operating temperatures are not very high. It also has the highest failure rate due to misapplication because it relies on someone to apply the correct type of loctite, in the correct amount, and also requires the system to sit for the appropriate curing time before being put into service.

 

[Diesel Dan]

We used safety wire on bolts that when they did break the bolt heads didn't fall into bad places. These could exceed 1" diameter grade 8, socket head cap screws etc.

Look up nord lock washers, another option.

 

[JimNC]

Safety wire = functional art
Castle nut = functional
Loctite = generally gets it done.

 

[cvairwerks]

Safety wire = functional art
Castle nut = functional
Loctite = generally gets it done.

High temp and/or vibration: Loctite is a fail. We safety wire/safety cable stuff that runs 500F and hotter, and the wire survives and the hardware doesn't turn, sometimes even at overhaul.

Safety wire or cable can be used on single bolts, screws or fittings, as it is often secured to drilled bosses, or around or thru structure, or to riveted or bolted tabs.

The only place we use Loctite is in small diameter hardware, on removable assemblies that live in closed compartments where a loose piece of hardware is not a flight hazard.

 

[elvee]

Safety wire also acts as a visual check - if the wire is in place then the hardware has been installed and tightened (generally). Loctite doesn't give you a visual check. We use a lot of safety wire on race bikes for this reason.

Functional safety wire pulls the bolt in the direction of tightening, and has to be kept tight for it to actually work.

 

[Innovate1]

Used to have a homebuilt airplane - long ago... As was stated safety wire needs something else to tie to, could be another bolt or some other thing nearby. As I recall it was used for oil pan bolts for example. Castle nuts with cotter pins might be used for prop bolts. They also make nuts with a section of plastic that creates friction with the threads for applications that aren't high temp. This type can be found in hardware stores and is fairly common for various uses. There are also nuts somewhat like castle nuts but the slots are just thin slits and the tips spring inward to grip the bolt threads. These can be used for high temp. Not sure how common they are for industrial uses but I am guessing they exist for other than airplanes.

https://www.aircraftspruce.com/catalog/hapages/an363.php?

 

[matt_i]

Also keep in mind that when using any screw into a tapped hole you can't use the castle nut.

It is a big pain drilling thru the external threads for a castle nut, a drill guide is better but that takes time to setup. Spot drill can also work. Drilling the hex heads or socket heads for safety wire and chamfering takes more time as well.

A lot of fasteners on industrial overhead lifting & hoisting equipment are safety wired due to a failure that could cause something to drop.

There was an oil-side baffle under the intake-lower on my BBC that I had to drill out the rivets to clean it up for the new longblock it was going on. I went back with #10-24 screws. Red loctite but safety wired the screws as a loose one was going right into the lifter valley not to mention a potential loose heatshield and having to tear the engine apart. So far all is calm

Just got an OTC safety wire twisting pliers for Christmas I have one spool of annealed stainless steel wire, they are sold at mcMaster Carr.

 

[ddawg16]

Nuts, bolts, fastening is a whole subject/engineering field just on it's own. Kinda like a doctor who specializes....

Don't forget, Nylock.

And think about this....

Crankshaft bolts....no lock washer....no Loctite....no safety wire....but yet they are subjected to tremendous vibration and temp changes.

 

[Bretny]

We dont know enough about the application to suggest a use.
We wouldnt go useing safety wire to hold a pin in the bucket of an excavator.

You can use thread locker on bolts. Its a bit harder to do that with castle nuts.

 

[vhol5]

Thank you for the comments! The knowledge on this forum always seems to amaze me. So my take on this so far, is that safety wire is not very common for uses other than aerospace or race vehicles, where failure would be catastrophic.

One reason I asked this question was because I own a pair of safety wire pliers that I have never used. I was wondering if I would ever have a use for them. I don't race or fly, so...

 

[ddawg16]

Thank you for the comments! The knowledge on this forum always seems to amaze me. So my take on this so far, is that safety wire is not very common for uses other than aerospace or race vehicles, where failure would be catastrophic.

One reason I asked this question was because I own a pair of safety wire pliers that I have never used. I was wondering if I would ever have a use for them. I don't race or fly, so...

What? You are contemplating getting rid of a tool?

One does not get rid of a tool just because he/she does not think they will ever have a use for it.

Just think, years from now, your children can take that tool and post a "What is it?" on GJ to continue the great tradition.

 

[rlitman]

Safety wire...
Castle nuts...
Loctite ...

Everything in your thread is excellent. I just have one thing to add regarding Loctite (anaerobic adhesive). It works well on ordinary steel bolts, but does not work as well on other materials. On stainless, for example, it requires a primer to activate, and even then, it isn't as strong. So, if your application is in stainless, then safety wire may make more sense.

 

[Diesel Dan]

Good video:Nord-lock

 

[ddawg16]

Good video:Nord-lock

Thank you.......that was a really cool video....I'm sharing that one with some guys

 

[iagsxr]

I don't safety wire a lot but would never get rid of my pliers or not have a roll of safety wire in my tool box.

Where it's really good out in the normal world is to retain things you can't with any other method. The oil fill cap on my race car engine is wired for instance. When we had our shop we sold and serviced grain augers. I wired tons of things on them that would otherwise vibrate loose over time.

 

[cvairwerks]

Safety wire and a set of pliers have enabled many emergency repairs and allowed one to limp home under their own power rather than coming home on a hook.

 

[unslow1]

That was a neat video. I had seen the Nord-lock but didn't know what they were called.

 

[gtae07]

Castle nuts on things that would be subject to rotation--hinge pins, landing gear joints, axle nuts, pushrod end connections, etc.

Safety wire on bolts/screws that must not come out but go into blind holes. Also used on jam nuts etc. that can't be locking.

 

[rburke65]

I didn’t think about the blind hole situation. Thx

 

[L5wolvesf]

High temp and/or vibration: Loctite is a fail. We safety wire/safety cable stuff that runs 500F and hotter, and the wire survives and the hardware doesn't turn, sometimes even at overhaul.

Safety wire or cable can be used on single bolts, screws or fittings, as it is often secured to drilled bosses, or around or thru structure, or to riveted or bolted tabs.

The only place we use Loctite is in small diameter hardware, on removable assemblies that live in closed compartments where a loose piece of hardware is not a flight hazard.

This is how I understand the differences.

A good read is the Carroll Smith book on fasteners (loosely referred to as 'Screw To Win' http://www.carrollsmith.com/books/

 

[cvairwerks]

Safety wire or cable is also one way to mechanically secure bulkhead nuts and electrical plugs in high vibration areas., or highly critical safety systems.

Almost forgot.... .020" copper is used as witness wire on certain switch guards and control handles...Move the guard or handle and the wire breaks...no question as to if it's been moved.

 

[JimNC]

High temp and/or vibration: Loctite is a fail. We safety wire/safety cable stuff that runs 500F and hotter, and the wire survives and the hardware doesn't turn, sometimes even at overhaul.

Safety wire or cable can be used on single bolts, screws or fittings, as it is often secured to drilled bosses, or around or thru structure, or to riveted or bolted tabs.

The only place we use Loctite is in small diameter hardware, on removable assemblies that live in closed compartments where a loose piece of hardware is not a flight hazard.

Agree, I was being a bit flippant. There was once a thread showing safety wire implementations, worth looking up if someone hasn’t seen it.

 

[Caboverbob]

Great thread - couple of comments on thread locking compounds -

•fasteners should be cleaned and primer applied prior to applying compound.
•if the fastener is turned AFTER the compound has cured, you need to start over - clean and apply fresh compound (I know lots of guys on Harley stunt bikes that simply retourque their chain sprocket bolts as a pre ride exercise not realizing that they've defeated the purpose of the compound they applied).
•be sure to use the correct type for your application (aluminum casting + steel bolt + red compound = damaged threads)

Nord Lok washers are pretty awesome IMO.

 

[shedfullatools]

Safety wire or cable can be used on single bolts, screws or fittings, as it is often secured to drilled bosses, or around or thru structure, or to riveted or bolted tabs.

Wait Wait Wait, do you safety wire the bolt, holding the tab, holding the safety wire for the original bolt?

 

[cvairwerks]

Lol, sorry Shed, didn’t mean to create a WTF moment there. In the aerospace world, we have fasteners that are known generically as “bolts”, but when installed, are permanently locked together. Some specific ones are Eddy bolts, Jo bolts, NAS4450 pins, et al. To remove them, the locking feature has to be destroyed, rendering the fastener unusable.

 

[poppakap]

Only a mention or two of nylock. I’ve always had good luck with them. Are they frowned upon?

 

[matt_i]

You'd think the structural steel in buildings would be safety wired but its ASTM A325 hex heads and torque-prevailing (deformed thread) hex lock nuts. I think the track record is pretty well proven by now.

 

[cvairwerks]

Only a mention or two of nylock. I’ve always had good luck with them. Are they frowned upon?

Nyloc’s have their place, but they are limited to an installation that stays below 250F. There are all metal locking nuts that are approved for temps to 500F and higher, but the increased cost might not justify the use of them.

 

[Bagherra]

That Nord-Lock vid was pretty good....

Being a helicopter mech..I'm quite handy with safety wire...

 

[kbs2244]

My 1953 Studebaker flathead six had the crankshaft bearing caps safety wired.
Heavy wire, like a coat hanger.

My dad, who fixed Navy fighters during WW II was impressed.

 

[Diesel Dan]

Have used these on big stuff and never had one loosen up.
Super bolt

 

[Diesel Dan]

Also used these to lock gears/hubs/rolls etc to shafts.
Ringfeder

 

[nadogail]

Safety wire can be used as a temporary repair or fastener.

I've used it as an alternative to plastic wire ties at times.