Threaded member tightening tool and counting apparatus

A counting apparatus for use in combination with a threaded member tightening tool having an engaging element fitting unit to which a threaded member engaging element is to be fitted, an electric motor capable of driving the engaging element fitting unit in either of a forward direction and a reverse direction, and a signal output unit, the counting apparatus being configured to be communicatively connected to the signal output unit, the counting apparatus comprising:

• a computing unit switchable between a counting mode in which the computing unit counts a number of tightened threaded members by receiving from the signal output unit a tightening completion signal indicating that the threaded member tightening tool has completed tightening of a threaded member and holds the counted number as a count value and a count return mode for returning the count value to a one-preceding count value;
• and
• a mode switching unit for switching the computing unit from the counting mode to the count return mode;
• wherein the computing unit returns the count value to a one-preceding count value in response to the computing unit having received from the signal output unit a drive signal indicating driving of the electric motor in the reverse direction with the computing unit having been switched to the count return mode, and the computing unit does not change the count value in response to the computing unit having received from the signal output unit the drive signal indicating driving of the electric motor in the reverse direction with the computing unit remaining in the counting mode and not having been switched to the count return mode.