This is a cross section view of a through hole that is threaded from two sides. In this case, the hole depth is too long to reach from one side only. However, it can be reached past the center from either side.

If this hole is selected to be threaded from both sides, there will be a discontinuity in the middle of the hole. This means that a bolt can only be threaded to roughly half the depth of the hole.

A designer may add a point at the bottom of a blind hole. In most cases, this represents the point left if a pilot hole is drilled with a drill bit. It may also serve a function to their design, or provide an area for chips that are generated during the threading process to fall.

If this point is added to the model, the threading will stop roughly 0.010" above the start of the point angle. Pilot holes are machined with end mills, not drills, so this feature is not required to be added to the model.

If a point at the bottom of a hole is present in a model, then the closest possible replication will be attempted based on the geometry and reach of the end mills used.