3.  Insert the stripped wire into the terminal lug barrel  until the wire insulation butts flush against the end of  the barrel. 4.  Squeeze the tool handles until the ratchet releases. 5.  Remove the completed assembly and examine it for  proper crimp. 1.  Strip the wire insulation to proper length. 2.  Insert the terminal lug, tongue first, into the hand tool  barrel crimping jaws until the terminal lug barrel butts  flush against the tool stop. Figure 4-105.  Insulating sleeves. Figure 4-104.  Inserting terminal lug into hand tool. Figure 4-103.  Preinsulated terminal lug. Aluminum Wire Terminals Crimping Tools 4-60 Stop Barrel butts flush against tool stop Tongue is horizontal Locator 1" (approximate) Tight or shrunk sleeve Loose sleeve Lacing cord Barrel Wire insulation Stripped wire Tongue Color-coded insulation Insulation grip Some types of uninsulated terminal lugs are insulated after  assembly to a wire by means of pieces of transparent flexible  tubing called sleeves. The sleeve provides electrical and  mechanical protection at the connection. When the size of  the sleeves used is such that it fits tightly over the terminal  lug, the sleeves need not be tied; otherwise, it should be tied  with lacing cord  [Figure 4-105] Hand, portable power, and stationary power tools are  available for crimping terminal lugs. These tools crimp the  barrel of the terminal lug to the conductor and simultaneously  crimp the insulation grip to the wire insulation. Hand crimping tools all have a self-locking ratchet that  prevents opening the tool until the crimp is complete. Some  hand crimping tools are equipped with a nest of various size  inserts to fit different size terminal lugs. Others are used on  one terminal lug size only. All types of hand crimping tools  are checked by gauges for proper adjustment of crimping jaws. Figure 4-104  shows a terminal lug inserted into a hand tool.  The following general guidelines outline the crimping  procedure: Aluminum wire is being used increasingly in aircraft  systems because of its weight advantage over copper.  However, bending aluminum causes “work hardening”  of the metal, making it brittle. This results in failure or  breakage of strands much sooner than in a similar case with  copper wire. Aluminum also forms a high-resistant oxide  film immediately upon exposure to air. To compensate for  these disadvantages, it is important to use the most reliable  installation procedures. Only aluminum terminal lugs are  used to terminate aluminum wires. All aluminum terminals incorporate an inspection hole that  permits checking the depth of wire insertion.  [Figure 4-106] The barrel of aluminum terminal lugs is filled with a  petrolatum-zinc dust compound. This compound removes the  oxide film from the aluminum by a grinding process during  the crimping operation. The compound also minimizes later  oxidation of the completed connection by excluding moisture 