To saw thin-walled metal pipe clutched in a vise — employment is not easy. Not only because the accompanying screeching grates on the ear. The work itself is difficult: in one direction the saw is more or less easy, but the other can’t get. Especially if the material is soft, e.g. aluminium. Put in place one of the saw blade two teeth towards each other. Cutting forces in both directions will be the same. Reduced and unpleasant sound cut metal.