A "blind" hole is one that is drilled, bored, or cast to a specific depth without breaking through to the other side of the workpiece. Unless you are Superman, daylight will not be visible when looking into a blind hole.
If you search the Web for solutions to problems experienced while tapping blind-holes, you will find more suggestions than you can shake a tap at. Perhaps it's simpler to start with the basics, and formulate options from there.
The first challenge when tapping blind holes is "chip evacuation". There is only one