Fastener driving tool

A fastener driving tool comprising:

• a housing;
• a cylinder including a first cylinder fixed to the housing and a second cylinder fixed to the housing;
• a combustion chamber frame movable in the housing and defining a combustion chamber in cooperation with the cylinder;
• a first piston slidably reciprocally movable relative to the first cylinder and displaced upon expansion of air/fuel mixture in the combustion chamber;
• a second piston slidably reciprocally movable relative to the second cylinder and displaced upon expansion of air/fuel mixture in the combustion chamber;
• a bit extending from the first piston and having a base end portion supported to the first piston and rotatable about its axis, and having a free end portion engageable with a fastener, the bit being linearly movable in accordance with the movement of the first piston;
• a rod extending from the second piston and having a rack, the rod being linearly movable in accordance with the movement of the second piston;
• and
• a motion conversion mechanism having a first part engageable with the rack, and a second part engaged with the bit for converting the linear movement of the rod into a rotational movement of the bit.