Patent ID: 8496534

Claim:
A group of taps with prepared hole cutting tools, each of the taps including, the prepared hole cutting tool having drilling edges for cutting a prepared hole; and a tap portion provided with a male thread corresponding to a female thread to be formed and thread cutting edges formed along chip discharging flutes provided to divide the male thread, wherein the tap portion is provided for cutting the female thread by the thread cutting edges on the prepared hole formed by the prepared hole cutting tool, wherein the prepared hole cutting tool and the tap portion are coaxially and integrally formed, wherein each of the taps has a diameter Dd of the drilling edges of the prepared hole cutting tool selected smaller than a valley diameter d 1 of the male thread of the tap portion, and an inner diameter D 1 of the female thread being determined depending on the valley diameter d 1 of the male thread, and wherein, when one tap among the group of taps has a larger protruding dimension from the tap portion to a top end of the prepared hole cutting tool than another of the group of taps, the one tap has a larger difference between the diameter Dd of the drilling edges of the prepared hole cutting tool and the valley diameter d 1 of the male thread of the tap portion than the another tap, and the drilling edges of the prepared hole cutting tool of the one tap have the diameter Dd smaller than the e diameter Dd of the another tap.