Safety wiring bolt heads, Do's and Don'ts...
- Thread starter RichLo
- Start date
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Try to use Loctite on a aircraft propeller or almost anyplace on a aircraft.
After working on aircraft so long i can't hardly bring myself to use Loctite as none of it seems to do a satisfactory job, but it is better than nothing.
After working on aircraft so long i can't hardly bring myself to use Loctite as none of it seems to do a satisfactory job, but it is better than nothing.
I saw your other post about twist per inch and immediately knew that you were in the Aircraft industry. If you have any more advice, memories or experiences to share about this topic or any others, you are more than welcome to post up my friend
Good question! Normally, stainless steel is what is specified by the relevant T.O.
(Technical Order, which as the name implies, must be followed by the Airman)
Also, there are 3 sizes that I'm aware of, depending on strength required.
(.020", .032", & .041") By the way, the number of authorized twists per inch
is dependent upon the wire diameter. (See following screen snap.)
NOTE: In some special applications (ie: something that a human needs to
be able to break in the cockpit during an emergency) we would use a .020"
copper safety wire on a cover over a genuine 'no-oopsies-allowed' switch.
****
EDIT 18-Jul-2023: Link to T.O. deleted due to a possible gray area violation of the FOUO.
Also removed internet address from screen snap. Remaining info does not reveal
any operational capability, which is always verboten.
Again, good question -- I don't get to wallow around in this stuff like I used ta! :0)
(partial screen snap of general safety wire guidance)
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Funny you say that, for I am of the opinion that
well-executed safety wiring can transcend the
basic safety-of-flight function & become a little
bit of senseless beauty that few get to admire.
Q: Is safety-wire of any real relevance to the
modern car/truck hobby? Is there a place where
safety wire is demonstrably better than loctite?
A: Safety wire finally solved an old
conundrum for yours truly. You see, I really
wanted to take advantage of the increased
performance that a good set of tuned headers
offered, especially if the factory manifolds had become
the bottleneck due to VE (Volumetric Efficiency) improvements
upstream.
The dilemma? I *detest* the sound of leaky header
flange gaskets. To me, that sound is a motorhead buzzkill
that cannot be overstated. For literally years I would
hope/pray that finally this time around the headers would
stay quiet...but try as I might, no joy, they would
always burn out, especially after high duty cycle
usage sessions. :-(
I tried every brand of gasket, made sure and kept
tightening the header bolts after so many thermal
cycles...until of course, life would intervene, the
header fasteners would fall victim to benign neglect...and
then they would inevitably loosen up, and the gaskets
would burn out. Again. Fuuuuudge!
(This was always the moment where I'd ask myself
why did I pick this as a hobby instead of something
normal people do, like being a foodie tourist, or
even golf? :0)
But then, while trolling the interwebs for something
else, the following photo revealed the secret:
Ford Cammer 427 on factory dyno undergoing max output reliability testing
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This is one of my very favorite engine photos of all time --
turning old dinosaur juice > heat > twist!
(exiting sound of WOT daydream) If you look carefully at the
interface between the exhaust header and the cylinder head,
notice that the first 1" of each primary is not glowing orange-red.
Why? Thanks to the newly installed, yet-to-loosen exhaust bolts,
both the exhaust header and the exhaust gasket sandwiched in-between
is running much closer to the temp of the coolant inside the
cylinder head's water jacket as opposed to the blazing hot
exhaust gas temps.
And *that* is the secret to the long-term reliability of a header
gasket -- keeping it as close to the water jacket temp as possible
will prevent burn out > blow out. (!)
****
Since this epiphany, any header-equipped engine I build I always
safety-wire the exhaust bolts. (Of course, only after the mandatory
thermal cycling/re-tightening dance has been done.)
Check this out -- here's a 383ci SBC in a '70 Chevelle that I rebuilt
for a friend:
Safety-Wired exhaust header bolts on 383ci version of the old 350hp/327ci SBC
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NOTE: This has been in service since 2015...8 years later, still
Long live safety-wire -- in some critical hot spots it's still worth the extra effort!
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More info on unrelated stuff.
The engineers at my company specify 6/8 twists per inch.
The second pic is how we do the prop hub on a PT6A. 8 bolts in a circle with about a inch space.
The engineers at my company specify 6/8 twists per inch.
The second pic is how we do the prop hub on a PT6A. 8 bolts in a circle with about a inch space.
You must be registered for see images attach
You must be registered for see images attach
On the off chance that this discussion has given you the impetus to
add another skillset to your collection, here's the last place I bought
a spool of .032" safety wire:
Note1: This is what I used on the SBC headers above. Easy to work with!
Note2: The price-per-use is really low -- the spool above is a lifetime supply
for anyone working at the hobby level. Heck, even if you do all your buddies'
cars it's still a lifetime supply. :0)
Of course, there are a few purists that eschew the pliers below & install their
safety wire by hand (and they make it look nice) ...but out on the flightline we
mere mortals always reached for the safety-wire pliers -- not only was it
faster, but the more uniform the wrap the easier it would pass inspection
by the Inspectors/QA folks.
Top entry = Mil-Surplus pliers for those who want to invest in the good stuff
Middle entry = entry-level pliers if you just want to buy & try
NOTE: If you are a tool snob you can spend a lot more, but unless you are on
a production line the 11" military surplus safety wire pliers will definitely get you
from here to there.
Few things are more relaxing/satisfying than installing
some safety wire. BTW, I've used plenty of loctite with
mixed results, especially in high heat areas like the
aforementioned header bolts. But safety wire has *never*
let me down. (!)
Hope someone finds this helpful. I do know that any/all
aerospace types will always point out the safety wire
when the hood is open at the local show & shine. Fun stuff!
add another skillset to your collection, here's the last place I bought
a spool of .032" safety wire:
You must be registered for see images attach
Note1: This is what I used on the SBC headers above. Easy to work with!
Note2: The price-per-use is really low -- the spool above is a lifetime supply
for anyone working at the hobby level. Heck, even if you do all your buddies'
cars it's still a lifetime supply. :0)
Of course, there are a few purists that eschew the pliers below & install their
safety wire by hand (and they make it look nice) ...but out on the flightline we
mere mortals always reached for the safety-wire pliers -- not only was it
faster, but the more uniform the wrap the easier it would pass inspection
by the Inspectors/QA folks.
Top entry = Mil-Surplus pliers for those who want to invest in the good stuff
Middle entry = entry-level pliers if you just want to buy & try
You must be registered for see images attach
NOTE: If you are a tool snob you can spend a lot more, but unless you are on
a production line the 11" military surplus safety wire pliers will definitely get you
from here to there.
Few things are more relaxing/satisfying than installing
some safety wire. BTW, I've used plenty of loctite with
mixed results, especially in high heat areas like the
aforementioned header bolts. But safety wire has *never*
let me down. (!)
Hope someone finds this helpful. I do know that any/all
aerospace types will always point out the safety wire
when the hood is open at the local show & shine. Fun stuff!
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Ah, youth. I raced flat track in the '70s and '80s, and every fastener with fluid behind it had to be safety wired. So yeah, 2 dumb youts with a Craftsman plug-in drill, a pair of vice-grips, and a tiny drill bit borrowed from a friend's Dad's toolmaker box with a half-hour of instructions and a promise of a summer of mowing lawns with the old reel mower if we broke it. I think we went through 5 or 6 that first year.
We push-cut a lot of grass.
We push-cut a lot of grass.
In practical terms...NONE. Maybe Jesse James, or Orange County Choppers, or some other made-for-TV, Total FantasyLand bullspit production would care, but it's not done in the real world. The hole in the bolt ends up wherever it ends up. The wire is strung through the hole so that the bolt can't turn in the "loosen" direction. The wire is formed/routed to the bolt hole, not the bolt hole getting drilled to best fit the wire routing. In other words, part of the "art" of safety-wiring is learning how to route the wire so that it secures the bolt effectively, AND is routed to fit the hole no matter how the hole is oriented.
Working at the Bus Company, we used genuine stainless safety-wire to secure thermal blankets to turbos, exhaust manifolds, and exhaust pipes. This is best thought-of in terms of putting on a pair of boots, only instead of using leather or fabric laces from bottom to top, you're using safety wire pieces, pulled tight, twisted, and cut between each pair of eyes or hooks.
I was the only person in the plant that had safety-wire pliers. The handle never got "cold" because when the blankets were going on, those pliers were passed from one guy to the next until all the blankets were on. I HATED installing those blankets, the outside was grey silicone-coated...fiberglass? But the inside was a loose stainless steel mesh holding ceramic fibers kinda like fiberglass padding, but higher-temp material than fiberglass. The effect was the same, though--fookin' ceramic fibers in the skin, itching.
Being that we weren't securing threaded fasteners, our technique was not so precise. OTOH, it more-or-less looked like the aircraft/military safety wiring, because the pliers put such a wonderful uniform twist into the wire. And, of course, we tucked the clipped-off end of the twisted wire into the blanket. Kept us from lacerating ourselves later.
I've never, ever used genuine real-true safety wire on a fastener. Read about it. Imagined it. Never actually practiced it. The Bus Company wanted us to "safety wire" the bolts used on driveshaft flanges at the transmission output flange. What they specified was totally insane. The Grade 8 bolts had been drilled in-house, through the THREADED SECTION not the heads. Then we put nyloc nuts up the threads past the hole in the bolt, and torqued, so that the nylon insert was shredded by the jagged ends of the holes stupidly drilled through the threads. Then they gave us non-hardened, non-Stainless plain ol' dirt-cheap "Mechanic's Wire" to loop through the holes drilled into two bolts, without ever going through the nuts. We twisted the two strands of wire linking two bolts, from the middle with an awl or Allen wrench, or whatever we could find. It was worse than merely stupid and wasteful, it was actually counterproductive due to the damage done to the nylon insert in the nut.
But that's what our moron "engineers" wanted, and they had the college degrees, not me. So we all did what we were told, for years and years.
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