what is the difference between a 1 4 and 1 2 router?
Greater Mass Router bits with 1/2-inch shanks have nearly four times the mass of 1/4-inch-shank bits, which translates into greater stability. The extra mass helps reduce what is known as "chatter," or vibrations caused by the high speed of the spinning bit. As you might expect, a more stable bit makes a cleaner cut.