Drill

Details Drill Drill

1999-09-14

2001-06-26

Wellington, A. L. (Department: 3722)

Cutting by use of rotating axially moving tool

Tool or tool with support

Having peripherally spaced cutting edges

C175S394000, C408S227000, C408S212000

Reexamination Certificate

active

06250857

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention is directed to a drill, which can be a multi-purpose drill used for drilling masonry as well as a drill for drilling wood or metal.
The greatest significance is accorded to a spiral or twist drill among drill tools, since it is considered the most important tool when producing cylindrical holes from a solid or for enlarging a predetermined hole diameter during a drilling operation. Its share of metal-cutting fabrication is estimated between 20% and 25%, and it is currently the metal-cutting tool that is produced in the greatest piece numbers and is most wide-spread. Viewed in simple fashion, a spiral drill is composed of a drill head, a drill shank that comprises a conveying helix and a plug-in end. What is referred to as a “double-thread” conveying helix is formed by two flutes or grooves arranged offset by 180°. The two-thread conveying helices fashioned in this way can buckle during drilling and lead to unstable drilling behavior.
SUMMARY OF THE INVENTION
The present invention is based on the object of offering a drill having a higher stability in the region of the conveying helix.
This object is inventively achieved by a drill having a drill head, a drill shank which comprises a conveying helix formed by at least two helical flutes and webs located between the flutes, and having a plug-in end lying opposite the drill head. The two flutes exhibit the same clear cross section at least in the end of the drill shank facing toward the drill head and arc arranged at an angle &agr; in the range of 130° to 170° relative to one another so that the flutes are not diametrically opposite one another.
It can thereby be provided that the relationship between the width B1 of the back face of the first web in a longitudinal direction of the conveying helix amounts to a 1:2 relationship to the width B2 of the back face of the second web in the longitudinal direction of the conveying helix.
In particular, it can thereby be provided that the first web merges into a back face at the end of the drill shank facing toward the drill head, and the back face interacts with the wall of the drill hole and extends over a distance S1=B1 in a circumferential direction of the drill, and the second web merges into a back face at the end of the drill shank facing toward the drill head that interacts with the drill hole wall and over a distance S2=B2 in a circumferential direction of the drill.
According to another particular embodiment of the invention, it can be provided that the slope h1 of the first flute corresponds to the slope h2 of the second flute. As a result thereof, the angle &agr; remains constant over the entire length of the conveying helix.
On the other hand, it can also be provided that the slope h1 of the first flute differs from the slope h2 of the second flute and the widths of the flutes can, thus, be varied.
It can also be provided that at least one of the slopes h1, h2 of the first and second flutes varies over the length of the conveying helix. The widths of the flutes can, thus, likewise vary.
Finally, it can be provided that the depth of at least one flute varies over the length of the conveying helix. A variation in the flute depth leads to a variation of the core of the drill shank. This leads to a greater flute transport cross section compared to conveying helices having the same outside diameter, this reducing and precluding the problem of blockage occurring, specifically given smaller drill dimensions with high drilling advance. The widths of the flutes can also be varied.
The invention is based on the surprising perception that webs having back faces of different size due to an asymmetrical arrangement of the flutes, i.e., not lying diametrically opposite one another, the conveying helix and, thus, the overall system is lent a higher buckling strength. As has been shown on the basis of a load analysis of the multi-axis stress and impact energy transport condition at prototypes, the inventive drills have, in detail, the following advantages compared to drills known from the prior art having flutes with the same transport cross section. These advantages are:
1. Higher stability with higher buckling strength given parameters that are otherwise the same;
2. Better impact energy transport with higher dynamic buckling strength under load of the pulses acting thereon given parameters that are otherwise the same; and
3. More advantageous vibration behavior given parameters that are otherwise the same.
Other advantages and features of the invention will be readily apparent from the following description of the preferred embodiments, the drawings and claims.


REFERENCES:
patent: 329174 (1885-10-01), Johnson
patent: 542223 (1895-07-01), Johnson
patent: 893162 (1908-07-01), Hackett
patent: 4579180 (1986-04-01), Peetz et al.
patent: 4913603 (1990-04-01), Friedli et al.
patent: 5078554 (1992-01-01), Kubota
patent: 5160232 (1992-11-01), Maier
patent: 2184373 (1987-06-01), None

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