Horizontal versus vertical pushbuttons
There seems to be a pretty major design flaw in all the vertical microswitch designs. A pushbutton is made of two pieces of plastic, barrel and plunger (these are just my descriptions of the parts, don't go asking an arcade operator for a replacement plunger, you'll look like a fool.) The barrel clips inside the plunger and has two plastic prongs sticking out the bottom. One of these prongs is in contact with the actuator on the microswitch. When you push the pushbutton the barrel moves down and closes the switch, here is where the difference between the two switch orientations comes in.
For a horizontally placed microswitch the prong on the bottom of the plunger pushes straight down on top of it. One of the central arguments for using vertical pushbuttons is that their configuration won't cause damage to the microswitch. Only extreme abuse can cause damage to the microswitch below the plunger in this configuration, so worry about damage is generally uncalled for.
In the case of a vertical microswitch the prong on the bottom of the plunger is cut off at an angle (narrow at the bottom and wide at the top), when the top of the plunger is pressed the prong slides past the microswitch and activates it that way. This is susposed to be a good thing as no matter how hard you press the button you cannot damage the microswitch. What usualy happens is:
- The prong on the bottom of the plunger slowly wears away and pushes outward, the button becomes less responsive (you really have to hit it to get a response. )
- The pushbutton was so badly made in the first place that there is room for the plunger to move side to side in the barrel rather than just up and down, if you don't hit the button dead centre the prong goes right past the actuator without closing the switch, causing errors during play.
One of the primary remaining reasons to use a vertical switch rather than a horizontal one is in cases where spacing is so tight in a control panel that you may have difficulty using a horizonal microswitch. Instances of this problem tend to be very rare, however.
(excerpted from main BYOAC site, originally described by Matt V.)