Abstract: A slotter provided with simultaneously two-way rotary saw blades comprises: an input shaft connected to a gear box by a power source, wherein a driving gear is disposed at the end of the input shaft of the gear box, a first driven gear engages with said driving gear and connects with a first driving shaft of which one end extends out of the gear box and retains a first saw blade. Furthermore, a second driven gear engages with the driving gear and connects with a transmitting gear at a second driving shaft, wherein said transmitting gear further engages with a third driven gear which mounted at the outer portion of first driving shaft by using a bearing, a second saw blade is disposed at a bearing seat of third driven gear such that the first saw blade and the second saw blade can simultaneously rotate in the deferent directions, thereby the reaction forces of the first saw blade and the second saw blade can be offset by each other so as to have a stable operation while in use.

Abstract: The present invention relates to a two-way rotary multi-function polisher, which comprises an input shaft driven to rotate by a power resource, a first spur gear and a second spur gear engagably transmitted by the end of input shaft; wherein the first spur gear is in response to the second spur gear and fixed to an output shaft having an inner polishing disc at the end thereof, so as to rotate the inner polishing disc in the first direction, while the second spur gear is coupled to a sleeve having an outer polishing disc at the end thereof and disposed to the exterior of output shaft by a bearing, so as to rotate the outer polishing disc in the second direction; hence, while the input shaft rotating, the inner and the outer polishing disc can respectively rotate in the opposite direction, enabling the two-way polishing and grinding to be achieved.

Abstract: A bicycle headset. The bicycle headset includes an upper bearing cover and a tapered ring that are made integrally in the form of a hollow arcuate circular ring capable of being fastened with precision.