Tool driving device and method of producing machined product

A tool driving device for cutting, the tool driving device being configured to be carried by hand, the tool driving device comprising:

• a spindle having a holder for holding a tool for the cutting, the holder being disposed at a distal portion of the spindle;
• and
• an electric motor for rotating the spindle,
• wherein a thrust bearing is attached to a housing of the electric motor, the spindle being contacted to the thrust bearing so that cutting resistance in a rotation axis direction of the spindle, transmitted from the tool to the spindle, is applied to the thrust bearing,
• further comprising:
• an annular pedestal disposed between the thrust bearing and the housing of the electric motor in the rotation axis direction of the spindle, the annular pedestal being disposed outside an output shaft of the electric motor, projected from the housing, at least a part of a thrust washer, on a spindle side, of the thrust bearing being projected, toward the spindle side, from an end face, on the spindle side, of the output shaft, by disposing the annular pedestal;
• and
• an adapter coupled to an end portion, on an electric motor side, of the spindle, the adapter having an annular flange contacted to the thrust washer, the annular flange being fixed to the output shaft and a gap being formed between the annular flange and the end face of the output shaft so that torque is transmitted from the output shaft to the spindle while the cutting resistance is transmitted from the spindle to the housing through the thrust bearing and the annular pedestal.