Abstract: A single point adjusting means for a rotary slotter used to transform sheets into box blanks is constructed so that each head is constructed of two sections normally locked together by a spring clutch. Each section carries a slotter blade and one section is keyed directly to the main drive shaft. The other section is selectively operable by a pneumatic power means between a cutting position wherein the spring clutch is engaged and an adjusting position wherein it is locked to the machine frame at an angular indexing position. At this time rotation of the main shaft will move the head section keyed thereto while the other section remains fixed thereby adjusting the relative angular positions of the slotter blades.Blade changing is facilitated by providing spring clamp means and a pneumatic actuated means for releasing the blade clamp.