Abstract: A band saw wherein one of the pulleys for an endless band-like blade is movable toward and away from the other pulley to relax the tension upon or to tension the blade. The one pulley is permanently biased away from the other pulley by a relatively weak spring whose bias can be overcome by hand to facilitate the removal of a blade or the application of a fresh blade. In addition, the one pulley is normally biased away from the other pulley with a pronounced force by a package of dished springs whose bias upon the one pulley can be interrupted by a single-acting cylinder and piston unit whose piston is installed between the dished springs and a reciprocable carriage for the one pulley. The dished springs react against a support for the pulleys and bear against the piston.