DE1059378B - Rotary bit with hard metal inserts in the blades - Google Patents

Description

GERMAN

INTERNAT. KL. E 21 C

PATENT OFFICE

S 51021 VI / 5b

REGISTRATION DATE: OCTOBER 26, 1956

NOTICE
LOGIN
AND ISSUE OF THE
EDITORIAL: JUNE 18, 1959

The invention relates to a rotary drill bit with hard metal inserts on the blades. Such Rotary bits have long been used to drill blast holes. at such bores are the feed forces due to the maximum possible dimensions for the drilling tool given. When designing the drilling machine, it is common to use a sharp rotary drill bit to base the dimensioning on the machining values that occur.

But since the hard metal cutting edges during the drilling process the constant pressure against the bottom of the borehole gradually rubs off and constantly widening, the cutting edge shape recognized as favorable for the machining process changes continuously. In the end the wear on the cutting edge becomes so severe that the drilling process in rocks with high strength and abrasion values come to a standstill very soon. It can only be used after replacement or regrinding the rotary drill bit can be continued.

In the known rotary drill bits, this is relatively often the case in hard rocks, so that with With the usual cutting edge shapes, the profitability of the drilling operation is bad from the start. That is expressed in the short overall service life of the cutting edges. Understood by the total service life the length of the borehole that can be drilled to the point of complete uselessness of the rotary drill bit leaves. It is made up of the individual service life (service life until regrinding) and the Number of possible regrinds. Experience has shown that there is the greatest carbide loss during regrinding occur, the total service life will be shorter, the less carbide is reworked the cutting edge must be ground away.

Attempts have been made to reduce wear by changing the feed rate, the speed and the shape of the cutting edge to reduce, but without particular success. With all of these measures to increase the overall service life one proceeded from the generally accepted assumption that the cutting edges already existed at the beginning must be sharp along their entire length and, above all, must be constantly re-sharpened. In contrast, the invention is based on the knowledge that with sufficiently high feed forces Drilling with a practically »blunt« cutting edge is also possible if you take care of it when drilling forces occurring on the cutting edge in a certain way on the known inner and to distribute the outer cutting edges of the cutting blades. If you also bring the cutting edge into a certain one Shape, the hard metal loss during regrinding can be entirely reduced in favor of the overall service life significantly reduce.

Rotary bit with hard metal inserts in the blades

Applicant:

Siemens-Schuckertwerke

Aktiengesellschaft, ίο Berlin and Erlangen,

Erlangen, Werner-von-Siemens-Str. 50

Dipl.-Ing. Karl Rosenwald, Erlangen, has been named as the inventor

For this purpose, the new rotary drill bit is characterized according to the invention by the following features:

a) The thickness of the hard metal inserts (I, II) is 40 to 60%) that of a comparable rotary drill bit with inserts of the same material embedded vertically in the blade wings, with negative rake angle and with the same maximum feed force;

b) the cutting edges of the hard metal inserts are inclined in a V-shape towards the axis of the rotary drill bit;

c) the rake faces of the cemented carbide inserts lie in the through the outer leg of the negative Rake angle laid shank material plane, and d) the cutting edges are at their outer end Ground to form sliding surfaces.

The size of the effective sliding surface is, depending on the strength of the hard metal, dimensioned so that the maximum wear surface that can be achieved through natural abrasion in this zone is a cutting surface Drilling is permitted until the wear surfaces forming on the inner cutting edges exceed a certain value. Only that occupied by the hard metal is under the effective sliding surface Understand the surface, as the softer shaft material grinds away prematurely when drilling.

In the relevant literature so far only drill bits have been described, each one or have other features of the rotary drill bit according to the invention. This is what hard metal cutting edges are like known, in which the blade wings are strongly V-shaped, or rotary percussion drills, the one have a negative rake angle (cf. among others the Swiss patent specification 313 133 and the Belgian Patent 519905). The hard metal cutting edges are because of their pronounced V-shape and

the large stone cone that forms during drilling primarily only for soft rock, Salts, for example, are suitable, while the carbide inserts in the aforementioned rotary percussion drills are almost double are as thick as in the subject matter of the invention and, moreover, are held vertically in the blade wings.

• It is ^: Furthermore, the use of sliding surfaces is known, namely with drill bits (cf. the cutting edges 1. In addition, the wear paths are greatest in this area and therefore a particularly strong carbide abrasion will occur.

The deliberate shifting of the greatest pressure forces into the due to the shape of the cutting edge The outer cutting zone could initially be viewed as a disadvantage, seen from the point of view of wear. However, doing this will increase the overall service life

U.S. Patent 1094 063). But you have significantly enlarged the rotary cutting edge there by

the only task the premature wear of the cutting edges in the outer zone, the zone greatest Wear and tear to prevent! In addition, they lie in the plane of the cutting edges, i.e. H. perpendicular to the drill bit axis.

Only in the interaction of all features according to the invention does it become. possible with practically blunt To drill the cutting edge while keeping the carbide losses small by regrinding but experiments with rotary drill bits, which have been designed according to the findings of the invention are shown that a single drilling operation yields drilling depths which are a multiple of the namely, the forces that occur are concentrated on a point where there is no significant increase the sliding surface can occur due to wear. The increase in the feed force depends only on the Increase in the wear bevel of the less stressed inner cutting edges. In the largest zone However, the hard metal inserts show wear, as shown particularly clearly in FIG. seen against the cutting direction behind the cutting edges 2 lying sliding surfaces 5, which with their lower side 6 already occupy the full carbide width. An enlargement of the sliding surfaces 5 over the specified dimension can therefore practically no longer occur when drilling. You »steer«

previously achievable drill location depths.

The drawing illustrates an embodiment in this way to a certain extent, the wear surface example; it shows . e-,, size, precisely at the point where the

Fig. 1 the blade wing surfaces of the rotary drill bit in front view, ^Λ · '

Fig. 2 shows the blade in profile, "Fig. 3 shows the top view of the rotary drill bit,

4 shows a worn rotary drill bit in a perspective view, and FIG

5 shows the pressure force as a function of the borehole depth in a graph.

In the case of the rotary drill bit according to FIGS. 1 to 3, the highest surface loads are always in the area carries the thickness of the hard metal inserts I, II only occur 40 of the outer blade wing zone and that up to 60% of that of a comparable rotary drilling unit - the sliding surface size is practically unchanged. Sees

in relation to the breaking away of the rock particles from the lightly loaded inner cutting edges 1 off, you have a practically »blunt«

wear is most effective.

So that a cutting drilling is possible, makes the presence of the sliding surfaces 5 on the Hard metal inserts the application of higher feed forces on the rotary drill bit is necessary than it is usually common. However, this is made possible by the design of the Rotary drill bit encountered. First of all, it is important

cut with inserts of the same material embedded vertically in the blade wings, with negative ones Rake angle and with the same maximum pre-thrust force. The inner cutting edges 1 of the hard metal inserts I, II are inclined in a V-shape towards the axis of the rotary drill bit and extend into the outer blade wing zone. Here they go into the outer cutting edges, forming the sliding surfaces 5 2 over that are relief-ground. The edges 1, 2 meet at the transition point under a blunt Angles to each other. The transition points are thus designed as cutting tips 3, which in the case of the Boh cutting edge in front of you. Nevertheless, the achievable drilling depths and the total service life are the new Rotary cutting edge considerably larger than with the known cutting edge shapes.

The drilling process only comes to a standstill when the less stressed inner cutting edges 1 have become dull. The sharp inner cutting edges 1, which can be seen particularly well in FIG. 3, are in the state according to FIG. 4 already strongly in the outer

Ren guided very close to the borehole wall 50 r.en sliding surfaces 5 grown into it.

will. The rake faces 7 of the hard metal inserts lie in the shank material plane laid by the outer leg of the negative rake angle β. The rotary drilling cutter body is cylindrical and has the plane-parallel surfaces 4 for the cuttings to flow away.

The slightly V-shaped course of the long inner cutting edges 1 and the presence of the cutting tips 3 act as a kind of two-point support during drilling. The rock located in the area of the inner cutting edges forms a rock cone during drilling - similar to the core drilling process - whose rock particles are broken out relatively easily by the inner cutting edges. The outer cutting edges, on the other hand, have to break the rock from the solid, so that the cutting tips and the parts of the cutting edges 1 and 2 immediately surrounding them are significantly more stressed during drilling than the further to rotary drilling order but also on this process, ie on the enlargement To be able to exert a "controlling" influence of the wear bevel on the cutting edges 1 and to absorb the aforementioned increased feed forces without damage to the hard metal inserts on the inner cutting edges 1, a strongly negative rake angle β is selected for the cutting edges 1 and a correspondingly steeply inclined embedding of the Carbide inserts selected. It offers good protection against hard metal breakouts and also allows the use of the low hard metal plate thickness. A grinding of the rake faces 7 when re-sharpening the inner cutting edges 1 is completely eliminated with this arrangement of the hard metals, so that the number of regrinds and thus the total service life of the cutting edge is considerably increased.

The "controlling" influence that the strongly negative rake angle β and the corresponding embedding on the wear process on the inner cutting edges

Exerts parts of the inner 70 located towards the cutting axis, lies in the fact that the wedge angle γ of the cutting edge

ι uoy D ι ö

The wing is divided practically in half by a solder felled from the bottom of the borehole onto the inner cutting edges will. Thus, left and right of the solder plane laid by the inner cutting edges are approximately the same Carbide parts. Therefore, the wear wear chamfers formed on the inner cutting edges can develop Enlarge only to the smallest possible extent during the drilling process. The one with the strong negative rake angle associated clearance angle α at the inner cutting edge is approximately 30 to 40 °. He is to be sharpened but the amounts of hard metal to be abraded are extremely small.

Should economic efficiency permit, the outer cutting edges 2 can also be relief-ground. This increases the individual service life, because the aforementioned sliding surface only changes in the course of the drilling process trains, albeit at the expense of the number of possible regrinds.

The results obtained with the new rotary drill bit emerge from the diagram according to FIG. 5. The feed force of the drilling device is plotted in it as a function of the borehole depth. Curve α shows the relationships for a rotary drill bit without carbide inserts, curve b for a rotary drill bit with carbide inserts, curve c the ratio for the new rotary drill bit without relief-ground outer cutting edge and curve d for the new rotary drill bit with relief-ground outer cutting edge. The specified maximum magnitude of the feed force P _max is shown in dashed lines.

According to curve c , with the new cutting edge, much greater drill hole depths can be achieved than is possible with the known cutting edges. The feed force is already very close to the maximum at the beginning of the drilling due to the existing sliding surface and deviates from it only very slowly during the drilling process, as the degressive course of curve c shows. This means that the drive of the drilling device is constantly fully utilized during the entire drilling process.

In cases a, b , the drilling device and the cutting edge must also be designed for the maximum feed force, but this is practically only reached as a limit value towards the end of the drilling process.

The gradual rise of curve c is based on the creation and slow increase of the sliding wear surface on the inner cutting edges or through the simultaneous growth into the only insignificantly increasing sliding surfaces 5.

Much greater borehole depths can be achieved if the rotary drill bit according to the invention is relief-ground on the outer cutting edges (cf. curve d). As long as the relief is not worn, the rotary drill bit behaves like the known drill bits according to curves α and b. As soon as the relief has completely disappeared, the effect of the sliding surface becomes apparent (see the kink in curve d).

It should also be noted that the cylindrical design of the rotary drilling cutter shaft the jerky jerking of the cutting edge, which is common with the known conical rotary cutting edges around the blade wings. In addition to protecting the cutting edge, this also protects the drill holes circular and no longer have the familiar triangular shape.

While with the known cutting edge shapes, the greatest carbide loss is due to frequent regrinding The wear surfaces that grow very quickly and over a large area occur, it becomes with the rotary drill bit according to the invention primarily only through the natural, low hard metal abrasion certainly.

The invention is not limited to double-edged rotary drilling cutters; it can also be applied to multi-edged ones Drill bits are applied.

Claims (4)

Claims: ■ 1. Rotary cutting edge with hard metal inserts in the cutting blades, characterized by the Combination of the following features: a) The thickness of the hard metal inserts (I, II) is 40 to 60 ° / o that of a comparable one The same rotary drill bit with inserts embedded vertically in the blade wing Material, with a negative rake angle and with the same maximum feed force; b) the cutting edges (1) of the hard metal inserts are V-shaped towards the axis of the rotary drilling cutter inclined; c) the rake faces (7) of the hard metal inserts lie in the shank material plane laid through the outer leg of the negative rake angle (β), and d) the cutting edges are ground at their outer end to form sliding surfaces (5). 2. rotary drill bit according to claim 1, characterized in that the cutting edges (2) of the Sliding surfaces (5) are relief-ground in such a way that only they are in engagement with the rock. 3. Rotary drill bit according to claim 1, characterized in that the wedge angle (γ) is practically symmetrical to the plumb line precipitated from the bottom of the borehole onto the inwardly inclined cutting edge (1). 4. rotary drill bit according to claim 1, characterized in that the rotary drill bit body and shaft have cylindrical shape. Considered publications:
Belgian Patent No. 519 905;
Swiss Patent No. 313 133;
U.S. Patent Nos. 1,094,063, 2,567,084;
"Glückauf" magazine, 1934, p. 824, ill., 2nd row, middle cutting edge V; "Bergbau" magazine, 1953, p. 169;
Journal "Technische Mitteilungen", Essen, May 1954, Volume 47, Issue 5, p. 229, r. Sp., Para. 1 and Fig. Ro Engineering and Mining Journal, August 1956, p. 77, fig. R. u. 1 sheet of drawings