Is it really necessary to stake the castle nut?

[outrider58]

Staking is not thread locking. Not in any end-all-be-all sense.

 

[jkeys]

Can you give us a little idea of your backgound so we can judge the merit of your suggestion?

I am a mechanical engineer. Work in DoD / automotive / robotics world. We are also a FFL with Class 2 SOT for DoD related weapons work. Robotic military vehicles that sometimes have all kinds of weapons attached.

 

[John from MD]

I am a mechanical engineer. Work in DoD / automotive / robotics world.

Thank you.

 

[clandestine]

Thread classes are pertinent to TDP parts for an M4 (AR). Loose thread classes can/will result in an AR coming apart if you don't do something to hold it together. The weapon whips violently when fired and wants to fall apart. Proper dimensions on parts and correct assembly keeps it together.

Staking is one thing that can help prevent parts from loosening, and threadlockers can be another. With the proper thread classes and staking, the castle nut won't loosen from use and operation.

Thread lockers are not part of the M4 program or part of a PIP. They are not needed if the parts are made to proper dimensions and proper lubricants and torque is used.

KAC rifles don't have threadlockers or staking on the castle nut. They generally don't come apart because of the tight thread classes used and machined receiver end plate.

If you have to use a threadlockers for your castle nut, you are likely using parts that are not made right (loose) parts that don't allow staking (too hard or too soft), or are using bad assembly techniques and hoping the threadlocker hides bad assembly. If you have to use a threadlocker, VC-3 is the safest since high heat is not required to remove it. Temps over 300 degrees can weaken an AR lower and upper. Fortunately with VC-3 you don't have to use more than 200 degrees or acetone to loosen it.

AR Manufacturers send their people to my classes. Industry professionals from all over the country attend my courses. Serious AR enthusiasts are the ones I enjoy helping the most, thus my advice here.

If my experience, procedures, and data was lacking I wouldn't be known for what I do.

I post to help those who want to learn.

 

[jrumann59]

Bold statement, and I respectfully disagree.

With modern threadlocker, then why do we still stake the gas keys? Same principles apply, more or less, to the castle nut. It is a chemical free, simple solution to a simple problem.

You can find examples of staking in modern manufacturing across many different products. Why don't we just pour threadlocker in everything then?

If you use threadlocker than fine. I don't care if you use elmers glue to secure your castle nut. But let's not go making uninformed statements about "what's better". If threadlocker was indeed a superior solution than I can guarantee you many manufacturers would have moved that direction.

Also, when threadlocker is applied, you can easily over-torque screws well beyond their design tolerances (scope rings are a good example). In some cases it may not matter, but in cases where proper torque values are required (resulting in proper clamping force), it can get tricky.

People do not realize how thread locaker can change torque values from a dry mechanical union to what is no now a "lubed" mechanical union. IIRC torque values can go up by 50% with loctite on the threads. So somthing torqued to 25 in/lbs is actually closer to 40 in/lbs

 

[jrumann59]

Yeah. You can definitely re-use them. Torquing it is so stupid easy. If you are building AR’s, and don’t have a torque wrench, you are dumb.

i have a torx wrench does that count....

 

[jrumann59]

On the plus side there are a handful of companies that have stakeless castle nut end plate setups....