Page 228 - Demo

226 ISCAR DEEP HOLE DRILLINGCoolant HoleThere are two types of cooling drills that depend on the diameter of the drill (Figure 6.5.2.10).Kidney HoleStandard for drill diameter less than %u00d88mmTwo HolesStandard for drill diameter equal or larger than %u00d88mmTubular StemThe cross section of the tubular stem is V-shaped with an internal coolant channel. Gundrill tubular stems can be solid carbide or steel.In the first case, the cutting tip and tubular stem are made from a solid carbide rod, which is soldered to the steel shank (Figure 6.5.2.11). The advantages of this design are high strength and rigidity, which contributes to the ability of drilling at higher cutting conditions which has a positive effect on productivity.In the second case, the drills consist of a cutting tip soldered to a steel tubular stem that is soldered to the shank (Figure 6.5.2.12).The V-groove steel tubular stem is obtained by cold rolling of pipes.The outer diameters of the tubular stem should be less than the diameter of the drill in order to exclude contact with the drilled hole surface.Figure 6.5.2.11BBAACCsection A-A section B-B section C-CFigure 6.5.2.12BBAACCsection A-A section B-B section C-C