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Tools for “Threaded Fasteners”
PLIERS
Pliers are ideal for holding and turning round pieces. They should notbe used on the heads of bolts and nuts because they will damage the head shape. The following are some common types of pliers.

• 
  Slip joint. General purpose tool with good gripping power.
  
• 
  Side cutting. For use in electrical work whenever wire mustbe cut.
  
• 
  Long nose or needle. For holding very small parts, or for working in tight places.
  

SCREWDRIVERS
There are two types of screwdrivers.

• 
  Plain. For useon slotted - head screws.
  
• 
  Phillips head. For use on recessed-head screws.
  

The screwdriver is made to tighten and loosen screws. It neither should nor be used as a chisel, punch, or prybar.


WRENCHES
Wrenches are used to tighten nuts and bolts. They are also used to hold metal parts.


Cutting Threads
Threading is the cutting of a spiral groove around the outside of a bolts or shaft or on the inside of anut or of a hole in metal. A top is the tool used to cut internal or inside threads. A die is used for cutting external or outside threads.
Many kinds of threads are used in industry. The most common series are national Coarse (NC) and National Fine (NF). For the same diameter bolt or nut, IheNational Finehas more threads per inch than theNational Coarse.
For example, a ‘A” diameter National Coarse has twenty threads per inch, while a 14” National Fine has twenty-eight threads. Below the 14” size, machine-screw thread sizes are used. For example, an 8/32 machine screw is made from No.8 wire as measured by the American screw wire gauge. It has thirty-two threads per inch. Metric threads are also used. Most threaded fasteners on automobiles are metric.
The coarse thread is lhe most common metric series. These are shown in Table 40-B. Metric fine threads have special uses. They are used on lhe tiny screws on eyeglasses and telescopes.
The diameter of a thread is measured with a drill gauge, hole gauge, or micrometer. The reading will be in inches or millimeters, depending upon the instrumentused.
To measure the pitch of customary threads, place an inch rule along the threads. Count the number of grooves or threads in one inch. This will give the number of threads per inch, or the pitch. Metric pitch is the distance between threads.


Thread Cutting
Hand taps, for cutting internal threads, are made as taper, plug, or bottoming taps. For a whole extending through a piece of metal, a taper tap is used. When cutting threads to the bottom of a closed hole, a taper tap is used first. Then a plug tap and, finally, a bottoming tap are use. Tae are held in a tap wrench.
Dies are used for cutting external threads. Dies are held in a diestock. A complete set of the common taps and dies in a wooden carrying case is called a screwplate. The size of the tap is stamped on the shank. The die size is shown on the face side.
TAPPING
In tapping, follow these steps.

1. 
   Select the correct size of tap. Insert it in a tap wrench.
   
2. 
   Select the correct tap drill.
   
3. 
   Lay out and drill thehole for tapping.
   
4. 
   Hold the tap square with the work. Turn lhe tap until the thread catches. Then apply steady pressure and give the tap one more turn. Apply a few drops of cutting oil near the point of the tap. Only steady, even pressure should be applied because the thread pulls the tap into hole.
   
5. 
   When the threads have been cut, back the tap off and clean out lhe hole. Test the threaded hole by interesting ascrew or threaded rod.