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Pins that won't quite go through castle nuts

inktomi

inktomi

Well Known Member
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Forgive my very chapped fingers :LOL:

I'm having a really tough time getting the cotter pins through these castle nuts on my rudder pedals. This is NOT a case of the bolt not being long enough, in fact I could probably use another washer to take up space. The issue is that the nut won't go on far enough to fully expose the hole. I've tried different nuts, different bolts - same deal - the hole is about 80% exposed when the nut bottoms out and therefore the pin won't go through.

What should be done in this case? I did try asking Van's support, but they don't understand that the bolt IS long enough - the nut just won't go on far enough before bottoming out to get the hole exposed. You can see in my photo the hole is not round.. but these nuts are already on as far as they'll go.

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So to be clear? The nut is bottoming out on the threads? So washers and scraping powder coating is not the solution...... You will have to chase the threads like Full Throttle suggested.
Take the bolt and nut out and thread the nut on with no washers present away from your rudder assembly and see whats going on. If you still can't install a cotter pin than you need to thread more. Make sure you are using the correct size cotter pin as well. Measure the length of your bolt so we can compare it to others lengths.
A

Edit: Pauls solution above would work as well.
 
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Ironflight said:
Try a thinner AN320 castle nut. Plenty strong in this application, and probably short enough to clear the hole in the bolt.
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I was going to mention this. The AN320 nuts are normally used with clevis pins instead of bolts (shear instead of bearing strength). They have a lower profile.
 
Here's a better photo - the nut is bottoming out on the threads, it's not a case of needing a longer bolt or needing to remove some powder coat.

I bet the AN320 nuts would work. I'll get a pack - thank you! I actually need to use a normal size washer there anyway - with the thin washer it's very loose. I only tried this to see if it would help - but it didn't and I just haven't put the full size washer back on yet.

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There can be all kinds of reasons that the manufacturer's QC department didn't catch (what appears to be) an error in "specs". If the threads are long enough, and the cross hole is in the specified position, then (if the nut is in spec) the nut should "take up" so that the correct size (another variable) cotter pin an be installed. It would seem like all these variables should be looked at in order to find the difficulty.

I would also agree with an earlier post reply, that since AN threads are of a "rolled" nature as opposed to cut threads, you would be ill advised to cut additional length to facilitate installation - bad juju for a stress riser (exactly where you don't want one ...).

YMMV - But there is a "mechanical" answer in there somewhere.

HFS

What is the bolt size & cotterpin you are using - thank you.
 
Norman CYYJ said:
As Paul said use a thinner nut, it is not wise to be cutting threads on bolts with rolled threads, it does cause stress risers. Let the wars begin.
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There's no war if only those skilled in such art reply; in fact, it is indisputable. This is another example where "xxx hours with no issues" replies mean basically nothing and potentially invite some serious harm.
 
Your picture tells the story. The nut is threaded to the bottom of the threads and it barely sticks out past the nut. The threads were not cut long enough. On a proper AN or NAS bolt, the nut will get to the bottom of the threads and it has gone past the cotter hole and there are 2--3 threads extending beyond the nut.

As Paul and others suggested, you might get by with a thin AN320 castle nut.

Or.

Just get another bolt. If you are really jonesin' to get it assembled, you could extend the threads with a threading die. The transition thread(s) on the die go a long way to reducing stress risers. And after all, this is a shear application with a bolt that is not even pre-loaded. So it would probably be "ok". But better to just throw it away and get another bolt.
 
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I am totally willing to use the proper bolts. I did buy a second set of bolts from Aircraft Spruce already, here's a photo. They all seem to be the same size on the threads. These are AN24-31 bolts and they matched what Vans sent with my kit.
 

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inktomi said:
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I am totally willing to use the proper bolts. I did buy a second set of bolts from Aircraft Spruce already, here's a photo. They all seem to be the same size on the threads. These are AN24-31 bolts and they matched what Vans sent with my kit.
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Clevis Bolts...Ah!

So you're going to need an AN320 shear nut...Screenshot 2025-03-27 at 1.03.57 PM.png
 
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I agree they’re more like screws than bolts, the slot head is super annoying to hold with a screwdriver. I already drew blood once with the screwdriver slipping trying to see if I could tighten the bolt to get the hole aligned (this resulted in me ordering a replacement set from spruce..).

They’re called AN24-31 Clevis bolts in the kit inventory.
 
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inktomi said:
I agree they’re more like screws than bolts, the slot head is super annoying to hold with a screwdriver. I already drew blood once with the screwdriver slipping trying to see if I could tighten the bolt to get the hole aligned (this resulted in me ordering a replacement set from spruce..).

They’re called AN24-31 Clevis bolts in the kit inventory.
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I wouldn't use them, EXCEPT catching clothing, ankle skin & bones on the bolt head is annoying :)
Since these used in a shear application, you don't need to torque them down.
 
So there's you're problem. It's a clevis bolt, not a bolt. Here's what I found, note the difference in thread lengths.

AN24-31: Thread Length: 0.324 inches minimum and 0.364 inches maximum
AN4 bolts: Thread Length: Between 0.438 inches and 0.515 inches (nominally 0.469, from what I can tell)

So no, a regular washer and nut are never going to work there. What part is this for, anyway?
 
Need an extra thread (in this application only)..... Just countersink the nut with the same size drill as the bolt.
 
Screenshot 2025-03-27 at 1.31.47 PM.png

It's specced as:

AN24-31
AN960-416L (Under nut)
AN960-416
AN310-4 nut
MS24665-208 pin

This is the bolt we're talking about.
 
From the 'Spruce website -- emphasis mine; sorry about the earlier misdirection...

Overview
Fabricated from steel and cadmium plated per QQ-P-416A, Type II, Class 3. AN310 castle nuts are used with drilled-shank bolts, clevis bolts, eye bolts and studs. The slots in the nut accommodate a cotter pin for safety purposes. The thinner AN320 castellated shear nut, with half the tensile rating of the AN310 nut, is used with clevis bolts and threaded taper pins which are subject to shearing stress only.
 
I just had the same problem. Didn't know about the shorter castle nuts. Since this is on the rudder pedals and not likely to shear off I went with the smaller cotter pin, the -132. It fit without any trouble and I had a bunch on hand.
 
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