Clamping device for clamping a turnable cutter blade on a tool holder

#The invention relates to a clamping device for clamping a turnable cutter blade on a tool holder, which clamping device includes a clamping jaw which has a two-arm lever construction, of which the front lever arm is supported on the upper surface of the turnable cutter blade and presses same against its support surface on the tool holder and of which the rear lever arm is supported in a centering recess of the tool holder, and a locking screw, which extends through an opening in the center part of the clamping jaw, which part lies between both lever arms, and is screwed into an internally threaded opening in the tool holder.

#In clamping devices of this type, the clamping jaw is stressed for bending in its center part which is weakened by the provision of the opening for the locking screw. In order to lend said clamping jaw the necessary bending stiffness, it must be constructed particularly high or thick in the center part or, however, also very wide. At any rate, such a bulky construction of the clamping jaw forms an obstacle for the discharging chips which are formed during the machining process. This is primarily annoying during an internal working, where the chip has only a limited area for its discharge. Random and irregularly formed chips are created in the openings through the clamping jaw, which occupy the entire free space and often cause considerable breakdowns, such as blade breakage and the forcing away of the drill rod by wedged-in chip balls, diameter deviations and roughed-up or rather damaged surfaces. If one forms such clamping jaws with small dimensions in the center part, then they do not have the necessary clamping force generating capabilities.

#The basic purpose of the invention is to provide a clamping device of the above-mentioned type in which the clamping jaw projects as little as possible above the chip surface and thus assures a good chip discharge, wherein the clamping jaw, however, also assures a good clamping with a high amount of clamping power. In a further embodiment of the invention, the clamping device is also inexpensive to manufacture and has improved handling capabilities.

#The invention is discussed in greater detail hereinbelow with reference to an exemplary embodiment which is illustrated in the drawing, in which:

#FIG. 1 is a central cross-sectional view of the clamping device taken along the line I--I of FIG. 2; and

#FIG. 2 is a top view of the same.

#Reference numeral 1 identifies a tool holder in the drawing; in the present case, the tool holder of a lathe tool. However, the clamping device can be used on any other desired tool for tool machines, for example, also on a boring bar or on a special tool. A recess 2 with a support surface 2a is provided in the tool holder for receiving therein a turnable hard metal cutter blade 3. Aside from this recess, the tool holder 1 has an internally threaded opening 4 which extends substantially perpendicularly with respect to the plane of the support surface 2a of the tool holder 1. An externally threaded locking screw 5 is threadedly received in the internally threaded opening 4. The locking screw 5 serves to hold a clamping jaw 6 which has a two-arm lever configuration, particularly a front lever arm 7 and a rear lever arm 8. The clamping jaw 6 has in its center part 9 between both lever arms an opening 10 for passage of the locking screw 5 therethrough. In order for the enlarged screwhead 5a of the locking screw 5 to project as little as possible above the upper surface 6a of the clamping jaw 6, the opening 10 has an enlarged section 11 for the complete reception of the screwhead 5a therein. The bottom wall 11a of the enlarged section is preferably constructed in a ball-cup-shape and the bottom pressure surface 5b of the screwhead 5a, which surface faces the bottom wall 11a, has the shape of a segment of a sphere.

#The clamping jaw 6 has on its side which faces the cutter blade 3, a projection 12 which is arranged coaxially and coextensively with respect to the opening 10 and is substantially cylindrical in shape. A cylindrical recess 13 is provided in the tool holder 1 and the internally threaded opening 4 is located in the center of the recess 13. The projection 12 is received in the recess 13 in the clamping jaw 6 and the hole 4 and opening 10 are axially aligned so that the locking screw can be effectively engaged with the tool holder 1. The projection 12 very substantially reinforces the clamping jaw in the center part 9; the clamping jaw 6 projects only with a small structural height h above the upper surface 3a of the clamping jaw. It has, in spite of this, a high bending moment and thus also a high clamping force.

#In the illustrated exemplary embodiment, the projection 12 tapers slightly toward its free end and has, therefore a frustum of a cone shape. The angle of the cone is approximately 10.degree.. The largest diameter D of the conical projection 12 corresponds approximately with the diameter d of the cylindrical recess 13. The clamping jaw 6 is centered relative to the tool holder 1 through this structure.