Combination of shorter drills and longer drills for deep hole processing

For hole depths greater than 40 diameters, we recommend using a combination of a shorter drill bit and a longer drill bit, so that the hole of the short bit can support the long groove of the longer bit. On a lathe or milling machine, it is generally not practical to start a single-bit flute gun drill with a drilling bushing.

Drilling supports, chip boxes, etc. are also unnecessary. Start drilling, drilling, reaming or boring to drill diameter plus .0005 ( plus .001 large), to 1 diameter deep, the shape of the bottom of the pilot hole is not important. Use oil or oil-based high "EP" water-soluble coolant with a concentration of 10-12 percent . Do not use synthetic coolants as they will not provide lubrication.

Insert the drill bit into the bushing or pilot hole dead spindle so that it starts from the bottom. Turn on the oil, coolant or mist in the spray system, start the spindle, and drill the hole to a continuous depth. When deepening, if there is a blind hole, return slightly to the bottom, stop everything and take off the drill bit. NEVER rotate the gun drill outside the hole. Pay attention to the outer corners and sides of the wear tip to establish a regrind interval. The proper tool life will depend on the material type, hardness, correct coolant type, pressure, speed and feed. The special nose grinding/contour combination is suitable for very deep holes, cross holes, intermittent cuts, special shapes, steps.