Nearly all wire and cable used as electrical conductors are covered with some type of insulation. In order to make electrical connections with the wire, a part of this insulation must be removed to expose the bare conductor. Copper wire can be stripped in a number of ways depending on the size and insulation. Figure 4-100 lists some types of stripping tools recommended for various wire sizes and types of insulation. Aluminum wire must be stripped using extreme care, since individual strands break very easily after being nicked.
The following general precautions are recommended when stripping any type of wire:
- When using any type of wire stripper, hold the wire so that it is perpendicular to the cutting blades.
- Adjust automatic stripping tools carefully; follow the manufacturer’s instructions to avoid nicking, cutting, or otherwise damaging strands. This is especially important for aluminum wires and for copper wires smaller than No. 10. Examine stripped wires for damage. Cut off and restrip, if length is sufficient, or reject and replace any wires with more than the allowable number of nicked or broken strands listed in the manufacturer’s instructions.
- Make sure insulation is clean cut with no frayed or ragged edges. Trim, if necessary.
- Make sure all insulation is removed from stripped area. Some types of wires are supplied with a transparent layer of insulation between the conductor and the primary insulation. If this is present, remove it.
- When using hand wire strippers to remove lengths of insulation longer than 3⁄4 inch, it is easier to accomplish in two or more operations.
- Retwist copper strands by hand or with pliers, if necessary, to restore natural lay and tightness of strands.
A pair of hand wire strippers is shown in Figure 4-101.
This tool is commonly used to strip most types of wire. The following general procedures describe the steps for stripping wire with a hand stripper. [Figure 4-102]
- Insert wire into exact center of correct cutting slot for wire size to be stripped. Each slot is marked with wire size.
- Close handles together as far as they will go.
- Release handles allowing wire holder to return to the open position.
- Remove stripped wire.
Solderless Terminals and Splices
Splicing of electrical cable should be kept to a minimum and avoided entirely in locations subject to extreme vibrations. Individual wires in a group or bundle can usually be spliced if the completed splice is located where it can be inspected periodically. The splices should be staggered so that the bundle does not become excessively enlarged. Many types of aircraft splice connectors are available for splicing individual wires. Self-insulated splice connectors are usually preferred; however, a noninsulated splice connector can be used if the splice is covered with plastic sleeving secured at both ends. Solder splices may be used, but they are particularly brittle and not recommended.
continuous runs. Solderless terminal lugs and splices are made of copper or aluminum and are preinsulated or uninsulated, depending on the desired application.
Terminal lugs are generally available in three types for use in different space conditions. These are the flag, straight, and right-angle lugs. Terminal lugs are crimped, sometimes called staked or swaged, to the wires by means of hand or power crimping tools.