Collet bush and tool driving device

A collet bush to be inserted into a concentric collet that is attached to a handheld tool driving device in order to position the tool driving device to a workpiece, the tool driving device holding, rotating and feeding a tool, the tool driving device having a holder for holding the tool, and a motor for rotating the holder, the tool driving device having a function to suck chips, the collet bush having:

• a tapered cylindrical outer surface for expanding the concentric collet;
• a cylindrical inner surface having:
• a first inner surface formed on a forward, distal side of the collet bush, the first inner surface forming a first through hole for slidingly fitting the tool;
• and
• a second inner surface formed on a rear, proximal side of the collet bush compared to the first inner surface, the second inner surface having a diameter larger than a diameter of the first inner surface;
• and
• a flow path for taking in air used for sucking the chips inside the collet bush, and
• wherein the flow path includes at least one second through hole formed between the outer surface and the first inner surface for taking in air used for sucking the chips, and wherein one end of the at least one second through hole opens at an end face on the distal side of the collet bush, while another end of the at least one second through hole opens at an annular face formed as a level difference between the first inner surface and the second inner surface.