The term double crimp is derived from the process of crimping the same tube used for the single flute gundrill, only crimping it twice, 180 degrees apart. Therefore, with the ﬂute channels on this type of tool being somewhat shallower then the single flute, they limit the type of materials to be drilled by the chip size generated. The most common materials drilled are cast irons and cast aluminum. The double crimp has advantages. First, the coolant holes in the gundrill body are formed by the crimping action; therefore, minimizing the coolant turbulence at the head/body transition.
Second, the flutes being equally swaged 180 degrees apart allow for much greater rigidity. The double crimp gundrill can obtain feed rates twice that of its single flute partner. This is obtained by two cutting edges opposed to one another, and geometry angles ground to precise dimensions. With the combinations of geometry, clearances and backtaper, the chip load is reduced by 50% and higher penetration rates are obtained, making the double crimp gundrill the tool of choice for applications with free chipping materials.
Star SU double crimp gundrill can be used for high penetration in softer materials. Diameters available from .1875" - .5625". Lengths are available up to 72."