A sheet feeder especially designed for use in the food and pharmaceutical industries is constructed in a hygienic manner and with suitable materials to permit rapid and effective cleaning and sanitizing thereof. Flexible, liquid impermeable bellows are mounted to the feeder housings in surrounding relation to the apertures through which the machine's several rotary shafts enter the housings. The bellows support bearing isolators that not only seal the housings from fluid entry, but because the bellows can flex, they also permit shaft spacings to be adjusted to adapt the machine to sheets of differing thicknesses and to set infeed belt tension. The sheet feeder's product input hopper and its discharge conveyor are designed to be easily detachable for cleaning in a dipping mode.