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Safety Wiring

Ever wondered about how to use safety wire?  Here are two articles to help explain the technique involved.  The first article is by an unknown author and from an unknown source (unfortunately), and the second is by the late Bill Phy who was a member of the Vintage MG Club of Southern California.  The articles were provided by Dave DuBois, Washington, USA.


Article #1

Author and source unknown.

Threaded fasteners are Safety Wired by the single-wire or double-twist method.  While the Single-Wire method may be used in a closely spaced closed geometrical pattern, on parts in electrical systems and in places difficult to reach, Double-Twist is the most common method of Safety Wiring.

 Figure 1 illustrates various methods commonly used in Safety Wiring nuts, bolts and screws. Observing this illustration, it will be noted that:

A.  Examples 1, 2 and 5 show the proper method of Safety Wiring bolts, screws, square-head plugs and similar parts when wired in pairs.

B.  Example 3 shows components wired in series.

C.  Example 4 shows the proper method of wiring castellated nuts and studs. (Note that there is no loop around the nut.)

D.  Examples 6 and 7 show a single-threaded component wired to a housing or lug.

E.  Example 8 shows several components in a closely spaced closed geometrical pattern, using the Single-Wire method.


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Article #2, Bill Phy.

On Tying It All Together Safety Wiring 101
by Bill Phy

The theory of safety wiring is simple!  The wire becomes tighter as the fastener tries to un-screw.  A&E or A&P practice spells out very specific details mandating wire size (always type 302 stainless steel) for each size fastener.  Our cars do not always permit such choices, particularly on external oil plumbing. These preclude the use of aircraft specs due to clearance constraints.  It really doesn't matter for lightly stressed engines like the XPAG.

The accompanying sketches show the proper wiring format for one and two fastener courses. More than two courses is discouraged.

N.B. Wire is always twisted clockwise and termination is bent back on itself to minimize occurrence of punctured fingers.  Note that fastener loosening is resisted by twisted portion of safety wire.

Tools for wiring depend on the mechanic's preference. I have (3) favorites.

  1. 8" Duck-bill pliers-jaws shortened by 1/2" and serrations stoned smooth.  These are great for clinching the initial lock.  I also grind the jaws thinner.
  2. Mini safety wire twister (U.S. Industrial Tool & Supply,* No. TP68-6 $58.95) Where space permits, this tool will produce the neatest span.
  3. E.Z. Wire Twister (U.S. Industrial Tool & Supply,* No. TP277 $11.75) Absolutely the best in tight quarters.

*U.S. Industrial Tool & Supply, 15101 Cleat St., Plymouth, MI 48170-6098 +1 800 521-7394



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