The length of the metal threads at the end of a spark plug is called the "reach".
The metal section at the bottom of a spark plug is called the shell. The components of a spark plug are the center electrode, an insulator, a metal shell, and side electrodes.
it must have threads and create spark
use just a little anti-seize on threads
Purchase the proper tap for the spark plug threads and use it to refresh the threads in the head. If the damage is more than slight then a heli-coil may be necessary. Remember to vacuum out the metal from the cylinder when you are done, a magnetic pick up tool may also work as will compressed air.
valve stem seals
Put JB Weld on the sparkplug threads.Screw it in to the non-fouler.Then it should come out.IN THE FIRST PLACE,PUT ANTI-SEIZE COUMPOUND ON THE MALE THREADS OF THE NON-FOULER,NEVER ON THE SPARK PLUG MALE THREADS.
no
sounds like you have stripped the threads, if so you need a " heli coil " thread repair..and follow directions. those threads will need to be repaired or retapped,and always start the threads on your spark plugs by hand and not with a wrench.
The threads in the head may be dirty. Try cleaning them out with a round wire brush. If that does not work, try a different plug. If another spark plug will not tighten, then the threads in the head are damaged and you need them professionally repaired.
If this happens, usually you crossed the threads on the head.
If your spark plug doesn't screw in your threads might be messed up. Run down to your local Part store and ask for a Thread Chasser($arround 10$) and screw that in to your spark plug housing just as you where screwing in a spark plug. What this does is it replaces the threads. Take out the chasser, Lubricate your spark plug and you should be good to go.
With a spark plug socket, a wrench, and a small piece of hose so you dont strip out the threads upon insertion....