Cutting by use of rotating axially moving tool – With means to apply transient – fluent medium to work or product – Including tool with duct
Patent
1995-07-05
1997-06-03
Rachuba, M.
Cutting by use of rotating axially moving tool
With means to apply transient, fluent medium to work or product
Including tool with duct
408 57, 408224, 761086, B23B 5102
Patent
active
056347472
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to spiral drills with indexable inserts.
2. Discussion of related art
Spiral drills comprise a spiral part with cutting edges at a tip end, and a shank part which to at least some extent is bounded by cylindrical surfaces. With spiral drills for metal drilling it is of great importance that no chips are packed in the spiral flutes, since even a small counter pressure from adhering chips will seriously disturb the chip formation and lead to greatly increased feed and cutting forces, as well as slower feed rate.
To facilitate the chip flow through the spiral flutes these should be made with a spacious cross section shaped to avoid pressing the chips against the wall of the hole. It is also suitable to supply liquid through coolant channels to openings near the cutting edges, which facilitates chip formation and lowers friction in the flutes. In order not to lower the torsion stiffness or give an undesirable coupling between axial force and torsion angle, the drill can be made with two spiral coolant channels as shown in the patents SE 335 111 and DE 33 04 277, located between the flutes in the ribs where they are least detrimental to the strength and stiffness. Those patents show how a drill can be made from a such a spiral part joined to a separately made shank part with different location of coolant channels.
It is also known through patent SE 194 706 to make drills with indexable carbide inserts in pockets on a steel body, where it has been made possible to utilize a limited number of insert sizes for a large number of drill diameters by using two or more unsymmetrically located inserts, one of which is a center insert close to the center line of the drill and one of which is a peripheral insert close to the periphery of the drill.
SUMMARY AND OBJECTS
The invention concerns a spiral drill with coolant channels which for the larger part of their length are placed where they detract as little as possible from the strength and stiffness of the drill, and to a smaller part near the cutting edges are located in relation to the location of drill inserts to give an optimal cooling and lubricating effect.
Previously known drills with spiral coolant channels have had channels continuing through the whole spiral part with constant position relative to the cross-section, whether they were made by twisting of a milled blank, forging or extrusion. In some cases where the drill blanks were forged, the channels were made before forging, filled with a substance with low melting-point and either not continued through the tip end face, or plugged at the end with a metal with high melting-point.
According to the invention coolant channels may be drilled in a cylindrical drill blank from the shank-part but not through to the tip end. The spiral part of the blank is then locally heated and twisted a predetermined angle. After twisting, the flutes, the insert pockets and other surfaces of the tip are machined using the channels at the shank part as an angle reference, and straight exit channels are drilled from exit openings in the tip face to meet the coolant channels. This makes it possible to locate the exit openings at optimal positions relative to the inserts without regard of the spiral channel location in the cross-section.
The insert pockets are unsymmetrically located, one near the center and one near the periphery. For best lubrication and cooling, the exit openings should be located at the same radius as the midpoint of the following insert, and thus one exit opening should be located closer to the center and one closer to the periphery, which is accomplished by drilling the exit channels after machining of the insert pockets.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described in detail with reference to the figures, where FIG. 1 shows a drill according to the invention, FIG. 2 an axial view of the tip end of the drill and FIG. 3 a drill blank prepared for twisting.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
REFERENCES:
patent: 2148805 (1939-02-01), Cogsdill
patent: 2541849 (1951-02-01), Villeneuve
patent: 3040605 (1962-06-01), Andreasson
patent: 3096668 (1963-07-01), Maynard
patent: 3117471 (1964-01-01), O'Connekk et al.
patent: 3504575 (1970-04-01), Makino et al.
patent: 3555935 (1971-01-01), Dorrenberg
patent: 4293251 (1981-10-01), Anderson
patent: 4583888 (1986-04-01), Mori et al.
patent: 4704055 (1987-11-01), Guhring
patent: 5509761 (1996-04-01), Grossman et al.
Eriksson Kent
Karlsson Leif
Tukala Tommy
Rachuba M.
Sandvik AB
Tsai Henry W. H.
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