Tapping machine and tap die, and method of detecting overstroke of tap

An adapter for tapping used in a turret punch press, comprising:

• a ring gear provided with a columnar through-hole at a central part of the ring gear;
• and
• a gear holder in which the ring gear is rotatably disposed and the gear holder is mountable on a turret of the turret punch press so as to locate the disposed ring gear at a position corresponding to a punch mounting section formed in advance in the turret of the turret punch press, wherein
• when a tapping tool is inserted into the columnar through-hole of the ring gear, the tapping tool is slidably moved in a longitudinal direction of the tapping tool in the columnar through-hole of the ring gear, wherein
• at least two ring gears are disposed, each of the ring gears is formed with a tooth portion at a peripheral portion of the each of the ring gears so that the tooth portion surrounds the columnar through-hole of the ring gear,
• each of the tooth portions of the ring gears are separated from each other in an extending direction of central axes of rotation of the respective ring,
• the tooth portion of one ring gear among the ring gears partially overlaps with the other tooth portion of the other one ring gear among ring gears when viewed in the extending direction of the central axes of rotation of the ring gears, and
• the gear holder is provided with an intermediate gear meshed with the ring gears.