Power tool

A power tool comprising:

• a housing having a rearward portion and a forward portion;
• a motor disposed in the rearward portion of the housing and having a motor output shaft;
• the motor being controlled to run at a speed of at least 15000 rotations per minute (rpm);
• an output spindle disposed at least partially in the forward portion of the housing;
• a rotary impact assembly disposed in the forward portion of the housing and including a cam shaft, a hammer received over the cam shaft and configured to move rotationally and axially relative to the cam shaft, an anvil coupled to the output spindle, and a spring biasing the hammer axially forward toward the anvil, the rotary impact assembly configured so that the hammer transmits rotational motion to the anvil without rotational impacts when a torque on the output spindle is less than a threshold torque and to apply intermittent rotational impacts to the anvil when the torque on the output spindle is at least the threshold torque;
• a transmission configured to transmit rotational motion from the motor output shaft to the cam shaft, the transmission having a gear reduction ratio of at least 14:1;
• wherein the power tool is configured to achieve a maximum fastening torque that is at least 1200 ft-lbs, and
• wherein a ratio of the maximum fastening torque to transmission diameter is at least 8.0 ft-lbs/mm, a ratio of the maximum fastening torque to transmission length is at least 30 ft -lbs/mm, and a ratio of the maximum fastening torque to transmission volume is at least 1.7 ft -lbs/cmΛ3.

A power tool comprising:

• a housing having a rearward portion and a forward portion;
• a motor disposed in the rearward portion of the housing and having a motor output shaft;
• the motor being controlled to run at a speed of at least 15000 rotations per minute (rpm);
• an output spindle disposed at least partially in the forward portion of the housing;
• a rotary impact assembly disposed in the forward portion of the housing and including a cam shaft, a hammer received over the cam shaft and configured to move rotationally and axially relative to the cam shaft, an anvil coupled to the output spindle, and a spring biasing the hammer axially forward toward the anvil, the rotary impact assembly configured so that the hammer transmits rotational motion to the anvil without rotational impacts when a torque on the output spindle is less than a threshold torque and to apply intermittent rotational impacts to the anvil when the torque on the output spindle is at least the threshold torque;
• a single stage compound planetary transmission configured to transmit rotational motion from the motor output shaft to the cam shaft, the transmission having a gear reduction ratio of at least 14:1;
• wherein the power tool is configured to achieve a maximum fastening torque that is at least 1200 ft-lbs with a ratio of fastening torque to tool length of at least 135 ft-lbs/inch and a breakaway torque that is at least 1700 ft-lbs with a ratio of breakaway torque to tool length of at least 200 ft-lbs/inch.