Fastening Tools
Ring Fasteners
Retaining rings (or snap rings) are used to prevent end-movement of cylindrical parts in bores or parts mounted on shafts. External snap rings are installed in grooves on shafts, whereas internal snap rings install in grooves inside a bore. Snap rings are installed and removed using snap-ring pliers.
Soldering Tools
Soldering is a process that joins metals by bonding a metal alloy to their surfaces. It is a low-temperature process that can be performed with simple tools and inexpensive materials.
Most solder is an alloy of lead and tin. The percentages of each metal in the solder will vary depending on the desired properties of the solder; e.g., its melting point. Higher percentages of lead will result in a lower melting point.
The most critical part of soldering is the cleaning of the surfaces to be joined. Any oxides or other contaminants on the surface to be soldered will prevent a solid connection from being made. The best way to prepare a surface for soldering is to use a flux that will clean the surfaces with a chemical action. Electrical connections require a rosin flux, and solders made for this will have the flux contained in the core of the solder. This is known as rosin-core solder.
There are a number of tools that can be used to generate the necessary heat to melt the solder, but in most cases a soldering iron is used. Most soldering irons are electrically powered, and can draw anywhere from 25 to 100 watts. Low-power irons would be used to solder electrical connections, whereas higher powered ones would be used in sheet metal work.
A tool that is often used for soldering electrical connections is the soldering gun. A soldering gun has a two-step trigger that allows the technician to quickly select a low or high heat setting. The main advantage to a soldering gun is the very rapid warm-up cycle. A soldering gun also has a light built into it for illuminating the work.
When soldering, start by mechanically cleaning the materials to be joined. This may involve the use of a stainless steel brush or even sandpaper. Heat the surfaces gently while applying flux to them, and then add solder once the flux has thoroughly cleaned the material. Tin the surfaces by spreading the solder thinly over the surface, making sure to thoroughly heat any area that is to be tinned.
Before soldering an electrical connection, it is always a good idea to make a solid mechanical connection first. This will involve stripping insulation from wires and twisting them together. Keep in mind that the entire connection needs to be heated before applying solder to it. If only the solder is heated and it then is “melted” onto relatively cool wires, a “cold” solder joint is created that can exhibit unusual electrical properties.
Welding Tools
When joining metals, the best way to achieve a high-strength joint is to use a welding process. Welding is very different from soldering in that it involves melting the base metal of the objects to be joined, a process that requires very high temperatures.
There are two major types of welding processes: oxyacetylene welding and electric-arc welding. Oxyacetylene welding involves the use of a torch that is fueled with oxygen and acetylene. Burning these two gases together creates an extremely hot flame, hot enough to melt steel and other ferrous (iron-based) materials. Filler rod is melted along with the base metal to produce a finished weld.
There are many specialized processes that fall under the electric-arc welding classification. The simplest and most easily recognized type is known as stick welding. Stick welding involves the use of an electric-arc welding machine and two cables: one that attaches to the work being welded through a ground clamp, and the other going to an electrode that is sometimes referred to as a stinger. The stinger is held by the welder and is used to hold the welding rod.
When the welder touches the welding rod on the work piece, an electric arc is formed. This electric arc generates a tremendous amount of heat and accomplishes three things. First, the heat melts the base metal of the material being welded. Second, the heat melts the electrode and deposits this metal in the weld as filler. Lastly, the flux on the outside of the electrodes burns and the generated gases form a “shield” around the weld. This gaseous shield prevents air from reacting with the hot metal and therefore weakening the weld.
As the welder continues the weld, the electrode burns and becomes shorter. The means that the welder must continue moving the stinger closer to the work until the electrode has been consumed. Once the electrode is used up, the welder “breaks off” or stops the arc, and a new electrode is placed in the stinger to continue the weld.
If more heat is needed to perform the weld, the welder can increase the amount of electric current that is supplied by the welding machine. Generally speaking, the larger the pieces that are being welded or the larger the electrode that is being used, the greater the amount of current required to get the weld done.
The electric arc that is generated during this process gives off a very high intensity light. The ultraviolet light is so intense that it can “sunburn” exposed skin and burn the retinas of unprotected eyes. Welders must, therefore, cover all exposed skin with protective clothing (preferably leather) and wear face shields (helmets) with light filters. The filters are usually very dark, so the welder can view the welding process itself but nothing else.
Newer welding helmets have electronic filters that “sense” the ultraviolet light from an electric arc and switch from “clear” to “shaded” in a split second. This allows the welder to leave the helmet down while lining up the next weld, saving the time consumed by flipping the helmet up and down.
Another electric-arc welding process that continues to gain popularity is MIG (metal inert gas) welding. MIG welding is also known as wire-feed welding because the electrode used for the weld process is a wire that is automatically fed from a spool. MIG uses a bottled inert gas (such as argon) to shield the weld, and requires a relatively sophisticated welding machine.
Let’s look at an example of how the ASVAB might test your knowledge of joining metal:
| Question | Analysis |
| The purpose of flux in metal joining processes is to |
Step 1: This question asks what function flux serves when joining metal. Step 2: There is nothing to simplify. Step 3: Predict that flux prevents oxidation by cleaning metal surfaces. |
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Step 4: Choice (A) matches that prediction. Eliminate choice (B), because although flux is used in the metal joining process, it is not the actual bonding agent. Eliminate choices (C) and (D), because flux is not intended to transfer electricity. |
Try out another example about fasteners on your own:
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Using which of the following tools absolutely requires the use of a protective face mask? - electric drill
- stick welder
- ratchet
- hand saw
Explanation
Which tool requires the use of a face mask? That would be the stick welder (B), which produces high-intensity light that could burn the skin and retinas if a protective face mask is not used. While it might be a good idea to wear a protective mask with the other tools, depending on the particular job, it is not always necessary.