Shrink fit- the pin is a few thousandths (.005" or so) larger than the hole, heat the part with the hole, chill the pin with dry ice or liquid Nitrogen, then get them together fast. As the pin warms and the outer part cools, they grow together.
Press fit- Pin and hole are the same size, and you use a press to put them together.
Slip fit- Pin is several thousandth smaller than the hole, you can press it in and out with no problem, friction or trapped parts make them stay together.
Interference- the pin is slightly smaller than the hole, but has knurling, a bend, or a flattened spot on it that makes it fit tightly.
Of course, the first two require some good dimensional control abilities. Most guns use slip fit, interference, or roll pins (always fit tight because they can compress slightly). And occasionally you will see tapered pins, which only fit one way and get tighter as you drive them in.
Last edited by Scorch; September 14, 2012 at 11:01 AM.