Abstract: A chain of a chain saw whose teeth are to be sharpened is mounted in a track (4) of a support table so that it can be indexed to a central cutting station whereupon a ram (12) will be acuated to reduce the width of the track (4) and grip the chain. A cutting device will then be lowered into contact with a tooth on the chain so as to sharpen that tooth. When the ram (12) is moved to the open condition the chain is indexed forward again by rotating a pusher arm (8) about a pin (9) while the pin carried on its own arm is driven in a forward direction. This causes an angled forked plate (10) to engage behind a tooth facing in one direction only (of the two possible directions). As the pusher (8) is moved back again a pin (29) rides up over a latch (30) onto the top face of the cam (31) so that the plate (10) can ride over the top of subsequent teeth carried by the chain.