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  • Writer's pictureJustin Schaub


Safety is an important thing, but not everyone performing maintenance or modifications completely take this fully into consideration.  Over 10 years ago, I went to school for aircraft maintenance and learned many procedures to keep the aircraft safe.  Lets face it, an airplane is not a car, and you can’t just pull over to the side of the road in the sky.  Airplanes are exposed to many different stresses, and physical changes while flying.  Either from vibrations of the engine, to G forces placed upon the structure, to the expansion and contraction of metal as the temperature of the air changes with altitude.  Making sure the mechanical components don’t fall out of the sky, safety devices are imperative.  So how does this relate to cars?  Keep reading.

First lets define the word safetying.  The FAA advisory circular AC43.13-1B (Acceptable Methods, Techniques, and Practices) defines it as, “Securing by various means any nut, bolt, turnbuckle etc, on the aircraft so that vibration will not cause it to loosen during operation.”  This same principle can be applied to cars, in fact, the drag racing and NASCAR communities have been doing this for decades.  I will say that a normal street car does not see the amount of stress an airplane or top fuel drag car does, but there are certain components, especially if you track your car, you should safety.  How does the old expression go?  Better SAFE, than sorry?

There are three basic methods for safetying and one or two you may be doing already.

  1. Safety Wire

  2. Safety Cotter Pins

  3. Self Locking Nuts

I am assuming most of you know what cotter pins and self locking nuts are, so I will focus this article on safety wire.  Safety wire comes in many different types of metal from stainless, monel, carbon steel, aluminum and even copper.  For our automotive applications we will be concerned with stainless steel wire only. 

There are two methods of safety wiring.  The double twist method, which is the most common, and the single wire method used on screws, bolts, and nuts that are in a closely spaced pattern, such as a circle. Safety wire must be installed in a manner that will prevent the tendency of the part to loosen.  This means if two bolts are safetied together, and you loosen one bolt, the wire will actually pull the other bolt tighter.  This tug of war approach is what makes it virtually impossible for two bolts to loosen.

To help demonstrate this method, review the images above.  Note: most automotive bolts are not predrilled for safety wire, but safety holes can be added with a drill bit.

So you may ask, that’s pretty cool, but how is it even possible to make such pretty twists like that?  Ah ha, well with most things in life there is a tool for that.  Of course, you can do this by hand, but we aren’t peasants.  Safety wire pliers or wire twisters can be found at Harbor Freight for around 10 dollars or picked up by any of your major tool suppliers.  These work by threading the wire through the first bolt, and gripping both pieces of wire with the jaws of the pliers. Then slide the outer sleeve down with your thumb to lock the handles.  You can know pull the knob on the bottom of the tool which spins in a spiral motion, twisting the wire.  After you have achieved 6 to 8 twists per inch, squeeze the handles again to release the wire from the jaws.  You are now ready to thread the wire through the next bolt, and repeat.

Now that you have mastered that, what is all this good for?  Some common areas of concern on a car you could safety would be the oil drain plug, transmission oil drain plug, cv axle to differential bolts, axle nuts, oil pump nuts, or any other fastener that would be detrimental if it came loose.  Remember, better safe than sorry.

PS, don’t forget your torque stripe, and please wear safety glasses

Build It. Race It.

Click to Buy: Safety Wire Pliers

                                                                                                                                                               [Photos of drawings are taken directly from the FAA advisory circular AC43.13-1B

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