6. Using the blade speed adjustment knob you can set the blade strokes per minute. The EX-21 is capable of producing 400 to 1550 strokes per minute. Normally harder/thicker material will require a slower blade speed. Set the blade around 800 to start with. If you notice burn marks slow down the speed. | 6. Using the blade speed adjustment knob you can set the blade strokes per minute. The EX-21 is capable of producing 400 to 1550 strokes per minute. Normally harder/thicker material will require a slower blade speed. Set the blade around 800 to start with. If you notice burn marks slow down the speed. |