Cutting by use of rotating axially moving tool – Combined cutting means – Including rotating cutter other than rotating – axially...
Patent
1991-06-27
1993-02-16
Bishop, Steven C.
Cutting by use of rotating axially moving tool
Combined cutting means
Including rotating cutter other than rotating, axially...
408224, 408230, B23B 5108
Patent
active
051865840
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a twist drill, particularly a drill made of solid hard metal.
It is known in principle to equip a twist drill with a countersinking device for the drilling of throughholes. This countersinking device is used after the production of a throughhole and provides the bore hole with a countersunk opening. Such a twist drill, equipped with a countersinking device that can be radially folded away, is structurally complicated and, since a certain structural space is needed, can be realized only on drills of a certain diameter.
SUMMARY OF THE INVENTION
An object of the invention is to provide a twist drill of the above mentioned type, configured so that it is able to produce a throughhole having a countersunk opening without the countersinking element being a separate component that has to be folded away and thus requires a complicated folding mechanism. A related object is to provide such a drill for use in the modern machine tool art, where path controlled milling machines, that is, CNC (computerized numerical control) milling machines, are employed for drilling such throughholes.
These objects can be attained by providing a twist drill which is characterized in that, in its region facing away from the drill cutting edges, the cutting member of the drill has a step forming a root clearance region, with the diameter of the root clearance region being greater than the core diameter but less than the drill diameter; in that transition stages are disposed between the spiral grooves of the drill and extend from the cutting member into the root clearance region, the transition stages being configured as ring segment faces which slope the direction toward the drill cutting edges and which have surface regions that conform approximately to regions on the surface of a cone; in that chip breaker grooves are provided at the spiral groove edges adjacent the ring segment faces in the cutting direction for forming undercutting edges; and in that cutting faces are provided adjacent the undercutting edges and extend from the outer portion of the cutting member into the spiral grooves. With such a twist drill, the countersinking feature can be easily realized by way of a circular milling process using a CNC milling machine. The twist drill is made of one piece and, thanks to its configuration according to the invention, is effective as a drill during the production of the throughhole and as a miller (namely, as a circular miller) during the production of the countersunk portion. By employing the special chip breaker grooves for the countersinking, an excessively negative rake angle on the order of magnitude of-30.degree. as a function of the helix angle of the spiral groove is avoided. The rake angle of the chip breaker groove preferably lies between+10.degree. and -10.degree.. The length of the root clearance region must of course be dimensioned in such a way that countersinking becomes possible at all. That is, the root clearance region must have at least the same length as the throughhole to be drilled (and better yet, a length greater than the length of the throughhole).
Another feature provides that the shoulders of the recess facing away from the drill cutting edges for countersinking the upper end of the throughhole are also configured for circular milling. This embodiment may be provided separately by itself, without the other recess shoulders being configured for countersinking.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a twist drill in accordance with the invention;
FIG. 2 is a side view of the drill according to FIG. 1, rotated 90.degree. about the drill axis in the direction of the cut;
FIG. 3A is a schematic representation of the drill during countersinking by way of circular milling;
FIG. 3 schematically illustrates the path of the drill during the countersinking procedure; and
FIG. 4 is an illustration of the drill during forward sinking by way of circular milling.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 illustrates a twist drill
REFERENCES:
patent: 1471866 (1923-10-01), Simpson
patent: 3122947 (1964-03-01), Cogsdill
patent: 4589310 (1986-05-01), Neumann
patent: 4589805 (1986-05-01), Duffner
patent: 4842451 (1989-06-01), Dugger
Escher Simon
Muller Gebhard
Bishop Steven C.
Hertel AG Werkzeuge & Hartstoffe
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