A rotary cutter (74) is rotated by a motor (76) through a drive and a belt (326) inside of a combination guard and belt tensioner assembly (260). The rotary cutter (74) includes a cutter head (82) having integral blade holders (92) which slideably receive knives (90) in a channel (230) each having a detent (236) which is received in an aperture (91) in the knife (90) so that no fasteners or moveable parts are provided for holding the knives (90) and adjustment of the knives (90) is not needed or allowed. Guard quarters (266, 314) and a guard half (268) are held in a closed position by a single latch (325). The guard half (268) includes an idler (300) which tensions the belt (326) in the closed position. The second guard quarter (314) mounted upon a pivotable cover (306) together with the mount (262) for the motor (76) defines an enclosure for the rotary cutter (74) and abuts with the guard half (268) in their closed positions.