I'd recommend LocTite Red 272.

https://www.grainger.com/product/4KL51?gclid=EAIaIQobChMI_sXG-va46AIVCh6tBh3Y2QZcEAQYBSABEgLfd_D_BwE&cm_mmc=PPC:+Google+PLA&ef_id=EAIaIQobChMI_sXG-va46AIVCh6tBh3Y2QZcEAQYBSABEgLfd_D_BwE:G:s&s_kwcid=AL!2966!3!50916684477!!!g!91281356757!

 

Plenty of thread there to double nut as well if you're OK with the look of two nuts.

 

Plenty of thread there to double nut as well if you re OK with the look of two nuts.

- Foghorn

Cheaper, too! Good recommendation.

 

Double nut. Peen a thread. Lock washers, either splits or star never worked. Drill and cotter pin. Just hit the bold with a hammer and bend it.

 

Hot dipped fasteners are made with greater clearance between the male and female threads than the Grade 8 fastener referred in your link. This is to allow room for the molten zinc coating. Because the coating is uneven, the thread mating clearance must be quite loose. Therefore, a nyloc but would be destroyed against the rough zinc just by threading it onto the bolt. I doubt anyone makes a hot dipped nyloc nut ! A nyloc nut requires a higher quality closer fit thread class than what you are using. A galvanized fastener is slightly better than dipped, and zinc plating even better than that. Plated may be the best compromise between cost, durability and desire to use a nyloc nut. If you stay with hot dipped fasteners, double nutting or staking the nut by peaning the male thread with a center punch are your best options. Keep in mind, nyloc nuts loose their locking ability after initial use…
My $.02 The Kentucky Toolsmith!

 

Menards and possibly HD carry hit dipped galvanized. Double nut and you should be fine. I have installed hundreds of street light, parking lot light, and traffic signal poles with single nuts, some with lockwashers, ( never had a lockwasher fail) some without, with no problems, so double nutting should cover you just fine. The only poles that fell were struck by a vehicle.

 

Menards and possibly HD carry hit dipped galvanized. Double nut and you should be fine. I have installed hundreds of street light, parking lot light, and traffic signal poles with single nuts, some with lockwashers, ( never had a lockwasher fail) some without, with no problems, so double nutting should cover you just fine. The only poles that fell were struck by a vehicle.

- ibewjon

Well, that was caused by the wrong kind of nut! The big one behind the steering wheel.

 

or you could stake them

rj in Az

 

I use regular zinc coated stuff on red cedar all the time outside. Sure it only lasts 10 years or so but i find my wife usually wants stuff completely changed way before that. I usually paint it all or use the waterproof exterior stain over everything

 

All - thanks for the great replies and suggestions. It sounds like double nutting / jam nut will be the safest and most cost effective.

In hindsight I suppose I could have used regular zinc plated since this swing set will only have another 5-8 years or so of life.

KYtoolsmith - I appreciate the detailed explanation. I realized the thickness on hot dipped galvanized is different but I didn't think about the coating damaging the nylon. This must be why such a lock nut is impossible to find.

Knockonit - what's "staking it" mean?

Menards and possibly HD carry hit dipped galvanized. Double nut and you should be fine. I have installed hundreds of street light, parking lot light, and traffic signal poles with single nuts, some with lockwashers, ( never had a lockwasher fail) some without, with no problems, so double nutting should cover you just fine. The only poles that fell were struck by a vehicle.

- ibewjon

Well, that was caused by the wrong kind of nut! The big one behind the steering wheel.

- Dark_Lightning

haha, good one!

 

Update, I e-mailed these folks yesterday as a long shot and they offered to sell me a small batch of 1/2" hot dipped galvanized (13 thread) nylon lock nuts:

https://www.lok-mor.com/products/prevailing-torque/n-loc/

Minimum order was $25 so I ordered a few extra and am all set. It sounds like they sell them all the time so hopefully the nylon won't have issues with the galvanized finish.