TM 1-1500-204-23-9 Change 4          7-11 (1)   Keep soldering irons away from flammable objects. (2)   In order to avoid burns, always assume that the tip is hot. (3)   Never rest a heated iron anywhere but on a metal surface or on a rack provided for this purpose. (4)   Never swing an iron to remove solder. (5)   When cleaning an iron, use a cleaning cloth or damp sponge . (6)   Hold small soldering jobs with your pliers or a suitable clamping device. c. Tinning.  If a soldering iron is new or the tip coat- ing is deteriorated, it must be tinned (coated with solder). To accomplish this procedure, proceed as follows: (1)   Hold the iron in a vise and file the point to its correct shape. (2)   Heat iron tip. (3)   While hot, file lightly to remove scale and old solder. (4)   Dip the point into a flux and apply solder, Federal Specification QQ-S-571, to the tip of the iron. The coating of solder will be bright and shiny and very thin. This aids in the rapid transfer of heat to the work. d. Soldering Procedure.  The following procedures must be performed in order to ensure a firmly soldered joint. (1)   Ensure  that  the  parts  to  be  soldered  are absolutely clean. While cleaning these parts, take care not to produce cuts or nicks which greatly reduce the mechanical strength of the wire, especially under vibra- tion. NOTE The joint should be prepared just prior to soldering. (2)   Securely join the parts to be soldered before any soldering is done. (3)   As shown in figure 7-23, hold the soldering iron  beneath  the  splice  being  soldered  with  as  much mechanical contact as possible to permit maximum heat transfer. (4)   Apply   the   solder,   Federal   Specification QQ-S-571, to the splice. NOTE Before the solder itself melts, the rosin core will have melted and run out over the splice to flux the area. (5)   When the solder has coated the splice com- pletely, the job is finished. A good, well-bonded connec- tion is clean, shiny, smooth, and round. It approximately outlines the terminal and the wire. e. Care.  The following paragraphs describe proce- dures for the care and upkeep of the different types of soldering tools. (1) Soldering  gun.  The  tip  of  a  soldering  gun should be removed occasionally to permit cleaning away the oxide scale. If for any reason the tip does become damaged, replacement tips are available. (2) Soldering iron.  Observe the following prac- tices for the care of soldering irons: (a)     Ensure     that     removable     tips     are securely fastened into the heater unit. (b)     Keep the tips clean and free from cop- per oxide. (c)      After completing a job, disconnect the powercord and, when the iron has cooled off, stow it in its proper storage area. (d)     When storing irons for long periods of time, coat the shaft and all metal parts with rust-preven- tive compound and store in a dry place.