DE2733395A1 - Counter boring tool for metal machining - has cutting edges set at given angles to reduce consumption and extend life - Google Patents

Abstract

The counter-boring tool has a shank (11) with four equally spaced radial blades (15-17). The angle of the cutting edges (18) on the end faces of these blades lies between 30 deg. and 35 deg. The helix angle of the outer edges (39, 40) of the blades lies between 40 deg. and 45 deg. w.r. t. the shank axis (12). The helix angle of the root (41) of the blades lies between 20 deg. and 25 deg. w.r.t. the shank axis. The front and rear edges of each blade run parallel to each other. The rear face of each blade lies approximately in a plane which is tangential to the shank surface. This design of cutter requires less operating power and has a much longer service life than conventional counter-boring tools.

Description

Piuf drilling tool, in particular countersinking tool

The invention relates to a Aufbonrwsrkzeug, in particular a countersink tool, with circumferential teeth wound helically around the core, each at the front end have a face cutting edge, and with each between the Rückonfläche and the Front surface of two circumferential teeth successively formed in the circumferential direction, flutes also helically wound around the core. äu # drilling tools this Art are usually simply referred to as countersinking tools.

Apart from so-called plan cores, with which, for example, flat surfaces on eyes Od. Like. Are leveled, are all other embodiments of countersinking tools intended for drilling and / or shaping pre-drilled holes. So you cut into the deep.

When designing the geometry of such countersinking tools the cutting edge geometry of other cutting tools is conventionally especially for turning, milling or planing, assumed. This has led to familiar cutting edge geometries can be easily identified from these cutting tools Has transferred countersinking tools. Well-known countersinking tools this kind accordingly have a small rake angle at the front cutting edges, e.g. in the Order of magnitude from 150 to 25 °, and consequently a large one Wedge angle from 650 to about 55 °. The helix corner is also called the helix angle or helix angle called, under which the flute runs to the tool center axis, is known from Countersinking tools extremely small. So the outer spiral angle is below the the peripheral teeth with their outer edge of the front surface on the tool outer diameter run inclined to the tool center axis, a maximum of about 25 °.

The inside spiral angle at which the circumferential teeth are connected to the Core adjoining inner edge of the front surface at the core diameter inclined to the tool center axis run, is in known countersinking tools on the order of a maximum of about 11 °. Known countersinking tools are therefore extremely compact in terms of structure. you Material content is relatively high. This compact (; design and the aforementioned Geometric dimensions lead to various disadvantages that were previously known as has necessarily accepted. The very small rake angle is the cause of swarf, for only small possible feed rates, for relatively short tool lives and for considerable high power consumption because only a small part of the provided Performance is converted into machining work, however, a significant proportion as a result the tool geometry is lost. Disadvantageous and reducing the service life Of course, the fact that the front cutting edge increases the risk of breakage also has an effect and are exposed to relatively strong crater wear. The resulting upsetting chips to strive for it; because of the poor chip flow, the operation is closed relatively often interrupt and relax quite often, which means that working time is lost. the The cutting geometry and the very weak spiral angle of the flutes are also Ur @@ che for a bad Spentlu0. The Sp.nabtuhr is inadequate. This is also the abortion of the at.

Machining developed, anyway, due to the small rake angle already high heat only relatively low, which further reduces the standing times.

The invention is based on the object of a drilling tool, in particular Countersinking tool, of the type defined at the outset, that is easier to set up and is designed to be more economical in terms of material content and, above all, larger feeds, considerably longer tool life, less tool wear and considerably better Chip flow and better chip and heat removal are guaranteed, as well as crater wear the cutting edge and their risk of breakage significantly reduced and even with lower power consumption enables considerably higher machining capacities.

The task of a boring tool, especially a countersinking tool, is of the type mentioned according to the invention solved by the following features a) The rake angle of the cutting edges is between 300 and 350, and b) the Outer spiral angle at which the circumferential teeth with their outer edge of the front surface on the outside diameter of the tool are inclined to the tool center axis each between 400 and 450 and c) the inner spiral angle at which the peripheral teeth with its inner edge of the front surface adjoining the core at the core diameter run inclined to the tool center axis, is between 200 and 250, and d) bsi each circumferential tooth runs the outer edge of its front surface at least substantially parallel to that of its rear surface and in the same way Align the inner lcants of its front surface at least substantially parallel that of its dorsal surface, and e) the dorsal surface of each peripheral tooth runs, seen within each radial plane along the tool center axis, at least approximately along a tangent, which in the area of the inner edge of the back surface to the core diameter is created.

This design according to the invention results in a boring tool, especially sinking tool, completely new design and significantly better cutting performance, and independent of size and diameter, i.e. suitable with this geometry for all sizes and diameters. Compared to known countersinking tools, about twice, larger rake angles avoids upsetting chips. The resulting, The face cutting edge, which is relatively thin in cross-section, considerably increases the cutting edge desired corkscrew formation with regard to the chips, so that the desired Let swarf reach. The feature a) also means that they are much larger Feeds enabled, the chip flow in the area of the face cutting edge is improved, very good chip and heat dissipation is achieved in the cutting area. The standing times for the front cutting edges are considerably increased, the cutting edge load and the Cutting edge wear significantly reduced. Since as a result of the feature a) the chip The crater wear is considerably reduced.

Furthermore, the risk of cutting edge breakage is significantly reduced. Almost all of the power provided by the machine on the tool holder can be converted into machining work, so that, for example, with the same power consumption the machining performance is increased significantly.

In tests, it was possible to increase the cutting performance by 100 % can be determined. The Features b) and c) in conjunction with feature a). The result is a strong one Spiral development. This leads to chip flutes that are very large in cross-section Significantly improved chip flow and thereby a more favorable chip and heat dissipation to ensure. This ensures that the achievable as a result of feature a) Twist or corkscrew chips also quickly and with as little loss as possible through the chip flutes can be dissipated, whereby the advantages achieved through feature a) actually can have an effect. For significantly improved chip flow from the smaller one Cutting diameter to the tool core contributes to the fact that the rake angle according to the feature a) and the outer spiral angle and inner spiral angle according to features b) and c) are specifically coordinated with one another. The features d) and e) are additional to the largest possible flutes in the cross-section with the relatively steep spiral pitch worked towards. The material cross-section of the individual circumferential teeth is accordingly relative small, which also benefits large flutes in cross-section. At the same time is achieved by the individual features a) to e) that the tool with respect to the Circumferential teeth relatively slender and narrow and overall light in structure and material content is permitted her to be more economical.

In an advantageous embodiment it is provided that the rake angle of the face cutting edges at least approximately the arithmetic mean value between Outer spiral angle and Corresponds to the inner spiral angle of the circumferential teeth. As a result, there is also a difference in the area of the face cutting edge Especially the rake angle between the outer diameter and the core diameter of the workpiece This was taken into account and also contributed to making an extraordinarily affordable Chip flow from the smaller cutting diameter to the tool core is achieved.

In a further advantageous embodiment, the clearance angle lies the front cutting edges each in the order of magnitude of about 40. The clearance angle is thus reduced compared to known countersinking tools. This angular design prevents pulling the tool into the material, especially when it is relatively soft, material to be machined.

It can also be advantageous if the rake angle of the face cutting edges each is 350. In a corresponding assignment, it can then be advantageous when the outer spiral angle of the circumferential teeth is 450 each and when the inner spiral angle the circumferential teeth are then 220 each.

It goes without saying that these angle specifications for all sizes and Apply diameter of the boring tools in question and to use can come.

In a further advantageous embodiment it is provided that the cross-sectional thickness of each circumferential tooth measured from the front surface to the back surface decreases steadily and with a small gradient from the core to the outer diameter of the tool. This improves the shape of the chip space, i.e. the cross-section and shape of the chip flutes in the direction that the best possible chip flow from the cutting edge into the flutes and through them for chip evacuation.

It goes without saying that the boring tool according to the invention has multiple cutting edges, e.g. as a three-cutter or also as a four-cutter.

The invention is shown below with reference to one in the drawings Embodiment explained in more detail. 1 shows a plan view of a four-edged Boring tool, FIG. 2 shows a side view of the tool in FIG. 1, FIG. 3 shows a Front view from below of the tool in FIG. 2, FIG. 4 a schematic, perspective View of a single circumferential tooth of the tool in FIGS. 1-3, FIG. 5 a pure schematic side view of the tool with simplified geometry and representation the angular relationships, FIG. 6 shows a schematic development of the outer tool diameter and tool core diameter with entered angles.

The boring tool 10 shown in the drawings, briefly also with Denotes countersink, has a core 11 with core diameter Di, which in the direction the tool center axis 12 is provided with a continuous axial bore 13 For example, a guide pin, not shown, can be inserted through the axial bore 13 be, which is fastened interchangeably, whereby the boring tool 10 to Countersink for countersinking drill holes for ~ screw heads.

Four circumferential teeth 14 - 17 are thus held in one piece on the core 11, which are wound helically around the core 11.

At its front end, at the bottom in FIG. 2, each peripheral tooth 14-17 has a face cutting edge 18, 19, 20 and 21 respectively. Each peripheral tooth 14-17 also has a front surface 23, 24, 25 or 26 pointing in the cutting direction according to arrow 22 and a back surface 27, 28, 29 and 30, respectively. Between the back surface and the front surface are two in the circumferential direction (arrow 22, Fig.1) successive circumferential teeth each axially continuous flutes 31, 32, 33 and 34 formed, which in the same The manner in which the circumferential teeth 14 - 17 are helically wound around the core 11.

The front cutting edges 18-21 are each ground free. Your open space is designated by 35, 36, 37 and 38, respectively (Fig. 3).

The clearance angle # is 40 in the example shown Vertical measured chip angle # is between 18 and 21 for each face cutting edge 300 and 350 and is selected as 350 in the exemplary embodiment shown.

The outside diameter of the tool is denoted by DA in FIG. 6.

In a tried and tested embodiment, this is the outside diameter of the tool DA selected to be 32 mm and the core diameter Di to be 13 mm. The spiral slope is elected to 100.

Further details of the tool geometry are given below Referring to Figs. 4-6, in part also to Fig. 2. It can be seen that each peripheral tooth, like the peripheral tooth 14 in FIGS. 2, 4 and 5, with its outer edge 39 of the front surface 23 on the outer tool diameter DA at an angle - below denoted by the outer spiral angle - runs inclined to the tool center axis 12. This outer spiral angle is between 400 and 17 for each circumferential tooth 14-17 450 and is set to 450 in the example mentioned.

Furthermore, it can be seen from Fig. 1, 2, 4 and 5 that with each peripheral tooth, as shown for the peripheral tooth 14, its inner edge adjoining the core 11 41 of the front surface 23 at the core diameter Di at an angle - hereinafter with Inside spiral angle denotes - runs inclined to the tool center axis 12. This The inner spiral angle for each circumferential tooth 14-17 is between 20 and 250 is set to 220 in the selected embodiment.

These angles are entered in FIGS. 4-6.

The development of the tool 10 shown schematically in FIG. 6 at Spiral pitch 100 makes it clear that the outer spiral angle on the tool outer diameter DA, that is to say at the outer edge 39 of the peripheral tooth 14, 450 and that the inner spiral angle at the core diameter Di, that is to say at the inner edge 41, is significantly smaller, namely 220 is. The rake angle t of the cutting edge 18 (Fig. 4, 5) is chosen so that that it is at least approximately the arithmetic mean between the outer spiral angle of 450 and the inner spiral angle of 220. That would be arithmetic result in a rake angle of 33.50, which is shown in dashed lines in FIG. 6. Of the actual rake angle? is rounded up in the selected exemplary embodiment fixed at 350.

Which through this geometry, namely the rake angle? of 350, the outer spiral switches of 450 and the inner spiral angle of 220, as well as the clearance angle d of 40 The advantages are explained in detail at the beginning. To avoid repetition is expressly referred to.

From the drawings it can also be seen that - as below the For a better overview only explained for the circumferential tooth 14 with reference to FIG. 4 - the outer edge 39 of its front surface 23 is at least substantially parallel to the outer edge 40 its back surface 27 runs. In the same The inner edge 41 of its front surface 23 extends at least substantially parallel to the inner edge 42 of its back surface 27.

In the manufactured and tested embodiment, this is parallelism exactly preserved.

It can be seen above all from FIGS. 1 and 3 that with each peripheral tooth 14-17 whose rear surface 27, 28, 29 and 30 - along within each radial plane seen the tool center axis 12 - at least approximately along a tangent runs in the region of the respective inner edge of the back surface 27-30 to the Core diameter Di is applied. As a result, for each peripheral tooth 14 17 is the cross-sectional thickness measured from the front surface 23-26 to the back surface 27-30 in each case from the core 11 to the outer tool diameter DA steadily and with a small amount Gradient decreases. The circumferential teeth are therefore in cross section, in the circumferential direction seen according to arrow 22, relatively thin-walled. This leads in conjunction with the described Dimensioning of the outer spiral angles and inner spiral angles to be extraordinary in cross-section large flutes 31-34 with at the same time good spiral guidance over the outer edge 39, resulting in an extremely good and lossless chip evacuation through the flutes 31 - 34 is guaranteed.

Claims (7)

Claims boring tool, in particular countersinking tool, with a helical shape Circumferential teeth wound around the core, each with a cutting edge at the front end have, and with two each between the back surface and the front surface formed in the circumferential direction of successive circumferential teeth, also helical Flutes wound around the core, g e k e n n n z e i c h n e t d u r c h the following Features: a) The rake angle (r of the face cutting edges (18 - 21) is between 300 and 350, and b) the outer spiral angle at which the peripheral teeth (14) with their Outer edge (39) of the front surface (23) on the tool outer diameter (DA) inclined to The tool center axis (12) is between 400 and 450, and c) the inner spiral angle at which the peripheral teeth (14) with their to the core (11) subsequent inner edge (41) of the front surface (23) inclined at the core diameter (Di) to the tool center axis (12) is between 200 and 250, and d) the outer edge (39) of its front surface (23) runs on each peripheral tooth (14) at least substantially parallel to that (40) of its back surface (27) and in the same way the inner edge (41) of its front surface (23) at least in the substantially parallel to that (42) of its back surface (27), and e) the back surface (27) of each peripheral tooth (14) runs within each radial plane along the Tool center axis (12) seen, at least approximately along a tangent that in the area of the inner edge (42) of the back surface (27) to the core diameter (Di) is created. 2. boring tool according to claim 1, d a d u r c h g e k e n n -z e i c h n e t that the rake angle (y of the front cutting edges (18-21) in each case at least approximately the arithmetic mean value between the outer spiral angle and the inner spiral angle the circumferential teeth (14-17). 3. Boring tool according to claim 1 or 2, d a d u r c h g e k e n n z e i c h n e t that the clearance angle (ci) of the front cutting edges (18-21) in each case is on the order of about 40. 4. Boring tool according to one of claims 1-3, d a d u r c h g It is not shown that the rake angle (t «) of the face cutting edges (18 - 21) each is 350. 5. Boring tool according to one of claims 1-4, d a d u r c h g it is not shown that the outer spiral angle of the circumferential teeth (14 - 17) each is 450. 6. Boring tool according to one of claims 1-5, d a d u r c h g it is not shown that the inner spiral angle of the circumferential teeth (14 - 17) each is 220. 7. Boring tool according to one of claims 1 - 6, d a d u r c h g e k e n n n n e i n e t that the from the front surface (23) to the back surface (27) measured cross-sectional thickness of each peripheral tooth (14) from the core (11) to the outer tool diameter (DA) decreases steadily and with a small gradient.