More Than You'll Ever Need to Know About Safety Wiring

By Chris Densmore

Safety wire is used to secure fasteners to prevent them from coming lose. It's used a lot in aviation and racing. To safety wire fasteners you will need safety wire, safety wire pliers, wire cutters (dykes), and needle nose pliers. In a pinch, you can make do with the wire and needle-nose pliers with a cutting edge. The hardest part of safety wiring is drilling the holes in the hardened fasteners. There are jigs available to hold nuts and bolts so they can be drilled more easily. You may also be able to purchase pre-drilled fasteners and save yourself some time. Safety wire comes in many types and sizes. You must first select the correct type and size of wire for the job. Annealed corrosion-resistant steel or stainless steel wire are used in race preparation. The following general rules apply to safety wiring: All safety wires must be tight after installation, but not under so much tension that normal handling or vibration will break the wire. The wire must be applied so that all pull exerted by the wire tends to tighten the nut. Twists should be tight and even, and the wire between nuts as taut as possible without over-twisting. Safety wire pliers can easily twist the wire too far, breaking or weakening it. For this reason, wire between nuts should be twisted with the hands. The use of pliers may damage the wire. Pliers should be used only for final end twist before cutting excess wire.
	Patterns All critical nuts except the self-locking types must be safetied; the method used depends upon the particular installation. The illustration at left shows various methods commonly used in safety wiring nuts, bolts, and screws. Examples 1, 2, and 7 show the proper method of safety wiring bolts, screws, square head plugs, and similar parts when wired in pairs. Examples 4 and 5 show a single threaded component wired to a housing or lug. Example 3 shows several components wired in series. Example 6 shows the proper method of wiring castellated nuts and studs. Note that there is no loop around the nut. Example 8 shows several components in a closely spaced, closed geometrical pattern, using the single-wire method.
Single Wire Safetying Insert the wire through each part consecutively in the direction that will prevent the part from loosening. Draw the wire tightly around each bend and twist the ends into a tight pigtail close to one of the safetied parts. Cut the pigtail square, leaving a minimum of three twists. Bend the pigtail over against the part being safetied to prevent snagging. You should not use safety wire longer than 24 inches for single wiring three or more parts as a group.
Double Wire Safety Wiring By Hand Pull the wire through the first bolt. Bend one end of the wire around the head of bolt #1 toward bolt #2, in a direction such that a pull on the twisted wire toward bolt #2 would cause bolt #1 to tighten. Twist the outer wire under the other wire close to bolt #1. Continue twisting the wire clockwise,keeping the strands wide apart to ensure a tight even twist. When the twisted pair reaches bolt #2 without slack, insert the wire in the the bolt hole in a direction so that bolt #2 cannot loosen without pulling bolt #1 tight. Bend the free wire around the head of bolt #2, and twist the wires counterclockwise. Continue twisting counterclockwise beyond the bolt to form a pigtail. Cut the pigtail square, leaving a minimum of three twists. Bend the pigtail over against the part being safetied, to prevent snagging.

Double Wire Safety Wiring Using Pliers Start by looping the wire through the fastener, using a little extra wire, because you don't want to be short at the end. Loop the wire coming out of the bottom hole around the bolt head clockwise and pull the wire tight with needle nose pliers in the direction of the second bolt. Start the twist by hand (two to three turns) then bring the two wires together and clip the safety wire pliers on the wires next to the hole it will go in on the second bolt, keep the two wires next to each other in the pliers jaws (no gap between them). Pull the safety wire pliers twist-knob to twist the wire, hold the pliers to keep it from twisting backwards and let the knob retract, then repeat until the desired twist is reached. Do not over-twist the wire, you can easily weaken or break it. Unclip the safety wire pliers, put one wire through the second bolt (using needle nose pliers helps), loop the other wire around the bolt head, start the twist by hand, clip on the safety wire pliers and twist. Now you're ready to cut the wire. Leave about 1/4 inch of a tail (about 3 twists) Tuck it around the last fastener so it doesn't snag.
Assorted Odd Bolt Heads and Nuts When various types of bolt heads and or nuts are safetied to stationary parts, you can use either right or left hand twists. Attach the safety wire in such a manner that if the bolt or nut should start to loosen then the wire would be in the direction of tightening the fastener.
	Alternatives Nyloc nuts are a good alternative, when applicable. The thing to remember is the nylon insert wears out after repeated use, and will not hold. Technically, they should only be used once. Also available are special washers as show. Torque the nut over these washers, bend the tabs up along the sides of the nut, and safety wire the perforated tab to something secure. Probably best to use these once, too.
Putting Holes in Your Nuts This need not be as painful as it sounds. You just need a drill with a very sharp bit, a vise to hold your nuts, a center punch, and a steady hand. Secure your nut, use the punch to mark where you want to drill, and carefully drill the nut. You'll want to lubricate the bit, to prevent overheating and premature failure. I've used DeWalt's 1/16" Cobalt bits with Lithium grease quite successfully. Bits aren't expensive, so you'll want to pick up two or three because they're very brittle, and break easily when bent. Apply light pressure, and coat the bit's cutting edge in grease occasionally. Be patient, and take your time. Ideally, the bit should not get hot. If it does, it's probably dull and should be replaced.	Click to view larger image.
	Suppliers of safety wire, pliers, and related items. You Favorite Scooter Racing Shop Progressive Suspension Lockhart Phillips USA
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© 2001-2002 Chris Densmore
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