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avt007
Topic Author
Posts: 1989
Joined: Mon Jul 10, 2000 4:51 am

Triwing Screws

Fri Feb 23, 2001 7:24 am

Has anyone else had the misfortune of having to work with these things? I've always suspected they were the work of the devil, but apparently, the Phillips screw company, not content with ruining the lives of every aircraft mechanic, decided to go one step further with this 3 sided fastener from hell. For some unknown reason, they are made so you can apply more torque installing them, than you can removing them! Please tell me I'm not suffering alone!
 
crjmech
Posts: 257
Joined: Wed Jun 07, 2000 6:31 am

RE: Triwing Screws

Fri Feb 23, 2001 8:00 am

Yeah, about half the CRJ is held together with the four-notched version of this screw. We call them Nazi screws since they resemble a swastika and are patently evil. They go in slicker than Hell, but are only good for a couple of removals before they round out. Any time we change a windsheild (held in exclusively by Nazis) or remove a panel, it's a given that about half the fasteners will have to be replaced. Not a good thing if you're on a road trip. I guess they're good if you're on the factory floor, but they're for sucks for those of us in the field.
 
VC-10
Posts: 3552
Joined: Tue Oct 26, 1999 11:34 am

RE: Triwing Screws

Fri Feb 23, 2001 8:11 am

Yes, I've used them on the DC-10, but I think you have it arse about face, the intention is more torque is applied to undo them. The ACW face has a larger surface area than the CW face. The problem they are made from titanium that is more brittle than steel.
 
avt007
Topic Author
Posts: 1989
Joined: Mon Jul 10, 2000 4:51 am

RE: Triwing Screws

Fri Feb 23, 2001 11:29 am

Luckily, the ones I battle with are not titanium (thank God!). The Dash 8 uses them all over, and my complaint is that the ACW face is angled, whereas the CW face is vertical. The result is the bittends to camout quite badly. Thankfully, Bombardier has provided alternate part numbers to use Phillips heads for the windshields. I`ve had share of fun with titanium,too. I spent an entire day trying to remove those half-moon, "hi torque" screws from a windshield. Why does the industry go out of the way to design such poor fasteners?
 
NKP S2
Posts: 1665
Joined: Mon Dec 20, 1999 3:16 am

RE: Triwing Screws

Fri Feb 23, 2001 2:15 pm

Thankfully, I haven't had to suffer tri-wings in years, with their patented "strip-o-matic" head design. Funny CRJ, I thought the term "nazi" screws was a term excusively used by us locally...didn't know it was such an industry standard term Smile F100's are infested with them. It wouldn't be so bad if the right tips were used, but what drives me nuts is to see them all distrorted from some yo-yo using a philips bit on them.
 
boomer
Posts: 108
Joined: Thu May 27, 1999 2:59 am

RE: Triwing Screws

Sat Feb 24, 2001 10:01 pm

I don't know how credible it is, but I recall hearing that the development of the tri-wing screw was intended to reduce the tendency for the head to get stripped during assembly processes where high-speed screw guns were used. The angles of the ACW face was to facilitate the automatic feeding of the magazine loaded tooling. I guess the consideration for the need to remove the screw was deemed unimportant.

I think most aircraft manufacturer's data provide for alternative replacements. Some, like the DC10, have restrictions regarding the use of cadmium-plated steel fasteners where titanium fasteners are later reinstalled. The cadmuim plating that rubs off in the threads of the nut or nutplate can later lead to corrosion and embrittlement of the titanium.
 
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DL_Mech
Posts: 2710
Joined: Fri Feb 18, 2000 7:48 am

RE: Triwing Screws

Sun Feb 25, 2001 8:56 am

I'll never forget the upgrade that Delta made to the multiplex system on the L-1011......We had to change every overhead decoder unit (above the PSU's) that control the reading lights, call lights and air valves. Lockheed had installed the original Telephonics units with round headed tri-wings and then covered them with some sort of shellac. It was almost impossible to access some of the fasteners, and the shellac made them even harder to remove. I used vice grips to remove most of them, and the spark that came off of them when your pliers slipped off was actually quite beautiful...........We did not have any kind words for any of the mechanics caught putting those "fasteners from hell" back in the airplane.
 
TurbineBeaver
Posts: 1511
Joined: Fri Jan 11, 2002 1:50 am

RE: Triwing Screws

Tue Feb 27, 2001 11:22 pm

I do not understand exactly what these look like/are! I do understand that they are screws/fasteners, but "triwing" and "three sided" doesn't help me any. Anyone have a picture or could provide a good description for me? I am VERY interested!!!


TB
 
L-188
Posts: 29881
Joined: Wed Jul 07, 1999 11:27 am

RE: Triwing Screws

Wed Feb 28, 2001 5:29 am

Who other then Snap-on makes a screwdriver that fits them??????
 
dash8tech
Posts: 708
Joined: Mon Jul 05, 1999 8:40 pm

RE: Triwing Screws

Thu Mar 01, 2001 7:27 pm

Oh yeah, on the Dash 8 100's and 200's (probably the 300 too, but I don't work on them). Luckily the Q400 doesn't have them.

Cheers.
 
tom2katie
Posts: 79
Joined: Sat Nov 11, 2000 8:58 pm

RE: Triwing Screws

Thu Mar 01, 2001 11:04 pm

L-188.. I buy a bunch of tri-wing bits at Boeing surplus everytime I am there. Much easier to get them that way.
 
Buzz
Posts: 694
Joined: Sun Nov 21, 1999 11:44 pm

RE: Triwing Screws

Fri Mar 02, 2001 2:49 am

Hi all, Buzz here. Take heart! the Boeings do not use them anymore, they use titainium screws/bolts with a #3 phillips head.
L-188 : i get tri-wing apex tips from the stockroom at work, no need to buy a special screwdriver.
I've noticed that you have to be -exactly- square on the screw head to keep it from slipping out. Not fun when the slots are torn up. We got 'em with the first of the DC-10's
Turbine Beaver: The accursed tri-wing has a Y-shaped slot instead of a phillips. The theory was there are twice as much area to unscrew as to screw it in. And there's a "handy" spot in the middle so you can start a drill/e-z out. Sort of like they knew ahead of time ther would be problems.
And they're made of A286 stainless steel, so if you drill it out and don't go V-E-R-Y slowly you over heat the A286 and it hardens instantly. Since it's Stainless steel, it's non-magnetic and doesn't corrode.
Take heart! the Airbus uses a 4 sided high torque screw heads. DON'T use a phillips on them, it tears up the head.
g'day
 
cdfmxtech
Posts: 1319
Joined: Wed Jul 05, 2000 11:37 am

RE: Triwing Screws

Fri Mar 02, 2001 9:01 pm

That is reason #527563 they I hate working on the DC10!!!!
 
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777wt
Posts: 828
Joined: Wed Jan 19, 2005 7:45 am

RE: Triwing Screws

Wed Jan 19, 2005 4:01 pm

TurbineBeaver, they look like this:
 
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HAWK21M
Posts: 30175
Joined: Fri Jan 05, 2001 10:05 pm

RE: Triwing Screws

Wed Jan 19, 2005 5:54 pm

777WT......What you doing in the Achives Today  Smile

TryWing.......Yeah I enjoy Installing them ONLY.
regds
MEL
 
320tech
Posts: 489
Joined: Mon May 17, 2004 11:38 am

RE: Triwing Screws

Wed Jan 19, 2005 11:41 pm

Tri-wings are a curse. The guy who designed them went straight to Hell, where he has to remove endless rows of stripped tri-wings.

At least I hope that's what happened. But why on earth does anyone think Phillips are better? They're trash screws, once in, once out. The screws Airbus uses (called Apex in a previous reply, but their proper name is Torq-set) are much better. The main problem there is that guys use too small a driver, and round them out.

The screws we should be using are Robertsons. God's screw.
 
amtrosie
Posts: 273
Joined: Thu Jan 06, 2005 6:44 am

RE: Triwing Screws

Thu Jan 20, 2005 4:13 am

LOL!!! I am rolling on the floor! The Dash-7's I worked on were the hell I lived with daily. We used valve grinding compound to help cut down on stripping of the heads. The "nazi" screws were far worse!! ATR's and Airbus have them and I hated them with a passion. Find a screw-knocker. They are the very best, If you have an air source. If not, my impact driver came out, and god knows they were in my toolbox when I had a road trip.
 
MD11Engineer
Posts: 13899
Joined: Sun Oct 26, 2003 5:25 am

RE: Triwing Screws

Thu Jan 20, 2005 6:25 am

Ever tried removing painted over Nazi screws? Also, use exactly the right size of bit (and there are several sizes, which look almost identical) to remove them, or else you´ll round them. When I was working on A320 overhauls, I bought myself a small air driven impact screw gun to get them out. Of course, afterwards the screws were trash, but it was better than a screwdriver or a speed handle if you´ve had to remove hundreds of the bastards during floor board removal.

Jan
 
User avatar
777wt
Posts: 828
Joined: Wed Jan 19, 2005 7:45 am

RE: Triwing Screws

Thu Jan 20, 2005 6:34 am

HAWK21M, still trying to find that GE90-115B blade making image  Nuts
 
G4Doc2004
Posts: 120
Joined: Thu Feb 19, 2004 7:49 am

RE: Triwing Screws

Thu Jan 20, 2005 10:13 am

The bits to remove the triwing and nazi bits are Apex bits. I buy them in bulk from Brown Tool or Cooper Tools. They are abugger to get out when they strip, esp the SS or titanium ones.......... Big grin
 
MD11Engineer
Posts: 13899
Joined: Sun Oct 26, 2003 5:25 am

RE: Triwing Screws

Thu Jan 20, 2005 10:34 am

What I´ve seen is that most people don´t know how to drill out screws, especially stainless steel or titanium, properly.
They use too much speed and don´t lubricate / coll enough, causing the drill bits to become soft (especially cobalt bits). In my experience go slow, use a lot of pressure and use some stuff like Boelube or Adrox lube sticks to keep the bit cool. Also interupt from time to time to let the bit cool down.

Jan
 
G4Doc2004
Posts: 120
Joined: Thu Feb 19, 2004 7:49 am

RE: Triwing Screws

Thu Jan 20, 2005 10:43 am

MD11Engineer, I know what you mean. Even some machinist cutting oil will do the trick to keep the bit cool, and a little Clover valve grinding compound on the end of the Apex bit on a worn out Torq-set or Triwing will do the trick to increase the "bite"
 
T prop
Posts: 979
Joined: Tue Apr 03, 2001 4:33 pm

RE: Triwing Screws

Thu Jan 20, 2005 9:15 pm

Phillips suck, I'll take Tri wings over them any day. If you use the correct size tool bit, are square on the screw and the joker before you who put the screw in didn't booger it up, there's no problem with Tri wings.

I've R&R'd a gazillion fuel tank panels, leading edges and other pieces on Dash 8's and when armed with a woodpecker or Johnson bar, I rarely have to drill any.


T prop.
 
UAL Bagsmasher
Posts: 1839
Joined: Wed Sep 08, 1999 12:52 pm

RE: Triwing Screws

Thu Jan 20, 2005 11:10 pm

Nazi bits...the scourge of the earth. The CRJ is loaded with the damned things. Most of those screw heads end up round as tires before you are done, if they aren't already roached out. It's no wonder I just bought a tub of Clover compound last week Big grin
 
User avatar
HAWK21M
Posts: 30175
Joined: Fri Jan 05, 2001 10:05 pm

RE: Triwing Screws

Thu Jan 20, 2005 11:56 pm

HAWK21M, still trying to find that GE90-115B blade making image
No probs.It'll be found.
regds
MEL
 
amtrosie
Posts: 273
Joined: Thu Jan 06, 2005 6:44 am

RE: Triwing Screws

Fri Feb 04, 2005 12:53 am

MD11Engineer;
Very true. One thing that helped alot with removing those screws (10-32's)was a 7/64 cobalt drill bit, run slowly. Followed by a #2 easy-out. The harder the material the slower the drill speed. ALWAYS USE A COOLANT!! This is machinist 101.
 
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HAWK21M
Posts: 30175
Joined: Fri Jan 05, 2001 10:05 pm

RE: Triwing Screws

Fri Feb 04, 2005 1:13 am

One thing that helped alot with removing those screws (10-32's)was a 7/64 cobalt drill bit
Only one time Installation.Very Expensive bolts  Smile
regds
MEL
 
LMP737
Posts: 6253
Joined: Wed May 08, 2002 4:06 pm

RE: Triwing Screws

Fri Feb 04, 2005 4:15 am

My only explanation for the existence of triwings was that an engineer caught his wife in bed with an airline mechanic and out of spite invented triwings.

Once I was working on an MD-11 up on the #2 engine area taking panels off forward of the fan cowl. Well all the panels were triwings, big ones to. After having to drill about a couple dozen out we decided that we would replace them all with standard Phillips so as not to "screw" the next guy who had to take the panels off.
 
MD11Engineer
Posts: 13899
Joined: Sun Oct 26, 2003 5:25 am

RE: Triwing Screws

Fri Feb 04, 2005 4:50 am

I had once the missfortune to have an easyout broken off in a drilled out screw.

Since then I use a cobalt bit 1/10 of a mm smaller than the shank diameter and drill / break off the screw head. Afterwards i´ll use the 7/64 bit and drill into the shank to get it out with an easyout, or I simply remove the panel and grab the shank with a small visegrips and remove it.

Jan
 
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HAWK21M
Posts: 30175
Joined: Fri Jan 05, 2001 10:05 pm

RE: Triwing Screws

Sat Feb 05, 2005 4:39 pm

Any Idea Why this type of bolt was considered to be used,Was it not foreseen that panels held by this bolt would require removal at some point in time.
regds
MEL
 
airplay
Posts: 3369
Joined: Sat Oct 25, 2003 1:58 am

RE: Triwing Screws

Sun Feb 06, 2005 1:23 am

Don't blame the designer of these fasteners. Blame the last guy who installed worn out screws. Many are too lazy to get some new ones from stores.

As mentioned before, as long as you use the right tool and technique, none of these fasteners are a problem.

Painted over screws need to cleaned before removal. Again, its not the designer's fault that people try to remove screws when they are obviously fouled with debris.

 
avt007
Topic Author
Posts: 1989
Joined: Mon Jul 10, 2000 4:51 am

RE: Triwing Screws

Sun Feb 06, 2005 7:19 am

No, I'll stick with blaming the designer, thanks! Definitely there is an issue with people using the wrong size bits, but even a brand new triwing is no great shakes. Does anyone make a triwing bit with the anti-camout ribs (ACR)?
 
amtrosie
Posts: 273
Joined: Thu Jan 06, 2005 6:44 am

RE: Triwing Screws

Sun Feb 06, 2005 8:43 am

Airplay;
Do you have stock in these style fastening heads? I never swore at anything til I encountered those buggers. Now I spout profanities while brushing my teeth!! And yes, I know how to brush, and floss too!! Take a close look at those [email protected]#&* tri-wings, the forward face (when tightening) has a 90 degree face while the backside is rounded out slightly. Truely, LMP737 is right. Someone has a very strong vendeta against A&P's.

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