Disks 1 and 2 rotate about fixed axes A and B. Knives a and b are mounted on bar 3 and slide 4 which are connected by turning pairs to pins c and d of disks 1 and 2. Disks 1 and 2 rotate in opposite directions. Knives a and b are always parallel to each other. By varying the speeds of rotation of driving disks 1 and 2 , the time when the knives meet may be changed, thereby regulating the cutting process.
$1451$LG,FD$