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Effect of Spring Pin thru Heavy Hex Nut
5

Effect of Spring Pin thru Heavy Hex Nut

Effect of Spring Pin thru Heavy Hex Nut

(OP)
We are installing a monorail system with track switches. The switches will be hung with rods and braced against lateral movement. A hanger fitting will be used at each mounting point, with the rod and nuts as shown. Is there any problem with drilling thru the nut and inserting a pin?

Thanks.

RE: Effect of Spring Pin thru Heavy Hex Nut

Yes, there are.

But, why would you want to do that in the first place when there are so many better faster easier cheaper ways to prevent a nut from "backing off", whatever that may mean to you.

RE: Effect of Spring Pin thru Heavy Hex Nut

(OP)
I would rather use a slotted hex nut but others wanted the spring pin method. Is there something other than a slotted hex nut that you can recommend?

Thanks.

RE: Effect of Spring Pin thru Heavy Hex Nut

Prevailing torque nut, either Nylon or all-metallic.
Loctite.

RE: Effect of Spring Pin thru Heavy Hex Nut

2
All the textbook calculation stuff aside...

Drilling a nice, straight, and centered hole in the end of a springy rod, up in the air, may be a "big ask".

Removing that pin after a few years in the weather might turn into a party...seized pin in the end of a springy rod, up in the air.

RE: Effect of Spring Pin thru Heavy Hex Nut

I'll second MJ, prevailing torque nuts are the way to go.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Effect of Spring Pin thru Heavy Hex Nut

Quote (Nescius)


Drilling a nice, straight, and centered hole in the end of a springy rod, up in the air, may be a "big ask".

Exactly.

RE: Effect of Spring Pin thru Heavy Hex Nut

2
Whoever 'wanted' to field drill and install spring pins have clearly never tried anything similar with their own hands.

Those persons should be removed from the design decision process immediately.

Mike Halloran
Pembroke Pines, FL, USA

RE: Effect of Spring Pin thru Heavy Hex Nut

Consider bend tab washers.

Ted

RE: Effect of Spring Pin thru Heavy Hex Nut

The safest are "lock wire nuts" they are used on aircraft machine guns against the worst vibration possible. Google for "lock wire nuts" you will find pictures. The nuts can be purchased already drilled for the use of lock wire.

RE: Effect of Spring Pin thru Heavy Hex Nut

You could also consider Nord Lock washers. A sales guy told us they used these on the rail industry.

RE: Effect of Spring Pin thru Heavy Hex Nut

Israelkk has the correct approach; safety wire on castellated nuts. Such work can be seen on aircraft propellers and engine mounts. It is time consuming to install and people doing the work have to be adept at such task.

RE: Effect of Spring Pin thru Heavy Hex Nut

I'm struggling to remember seeing lockwire used on anything quite as big as 3/4" UNF.

A.

RE: Effect of Spring Pin thru Heavy Hex Nut

Castle nuts and lockwire-ready bolts do exist in those sizes, but they are very expensive. Several dollars per nut, without even considering the bolt that is required to match.

The spring pin method will likely be equally expensive when you have to hand drill every single nut and bolt in your assembly, assuming your assembly crew makes more than a few dollars per hour.

Tab washers, liquid threadlocking compound, and other methods will solve your problem. If it were me, stainless steel (or high strength, depending on loading conditions) prevailing torque nuts would get the nod.

RE: Effect of Spring Pin thru Heavy Hex Nut

I worked on a job for a French tire manufacturer. They were standardized on nord locks. If you go with a drilling the nuts, I'd pilot drill them in the shop.

http://www.nord-lock.com/nord-lock/wedge-locking/

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