Abstract: A dovetail tool changer includes a first plate to be constrained to an external handling system, a second plate to be constrained to a tool and locking device to lock the second plate in the first plate. The second plate is insertable along a longitudinal direction in a pocket defined in the first plate, both plates have complementary cross sectional shapes and define a dovetailed coupling. The locking device includes at least one floating element movable between a lock position at which it exerts a thrust onto the second plate preventing disengagement thereof from the first plate, and an unlock position, at which the second plate can be separated from the first plate. The locking device includes at least one thrust element connected to the at least one floating element, which are together able to be displaced along a first direction in response to an exerted user force.

Abstract: A bit holder that includes a front portion and a shank axially depending from the front portion. The front portion having an axial length that is less than the axial length of the shank. A combination bit holder and base block that includes the bit holder with the front portion having an axial length that is less than the axial length of the shank. The base block including a mounting portion and a device receiving portion, the device receiving portion including a length that is the same or less than a length of the mounting portion. The base block having a device receiving portion that includes a length shorter than a length of the mounting portion adapted to provide increased access to the rear of the bit assembly allowing the base blocks to be mounted closer to each other for micro-milling operations. Shortened bit holder shanks are reconfigured from prior art to provide increased holding power between the bit holder shank and base block bore.

Abstract: The present invention belongs to the technical field of milling machines, and mainly relates to a novel cutter holder and base system for a milling machine. The cutter holder and base system according to the present invention aims to solve the problems in the prior art that a cutter holder structure is unreasonable, the cutting force of a cutter cannot be well dispersed in the cutter holder and a base, so that the service lives of the cutter holder and the base are shortened. The base is provided with a hole-shaped inner area and two curved surface areas, where the two curved surface areas are disposed in a circumferential area of the hole-shaped inner area, the curved surface areas are arranged at an angle, and each curved surface area includes two curved surfaces. The cutter holder improves its own usage performance while a lighter weight is achieved.

Abstract: A bit holder that includes a front portion and a shank axially depending from the front portion. The front portion having an axial length that is less than the axial length of the shank. A combination bit holder and base block that includes the bit holder with the front portion having an axial length that is less than the axial length of the shank. The base block including a mounting portion and a device receiving portion, the device receiving portion including a length that is the same or less than a length of the mounting portion. The base block having a device receiving portion that includes a length shorter than a length of the mounting portion adapted to provide increased access to the rear of the bit assembly allowing the base blocks to be mounted closer to each other for micro-milling operations. Shortened bit holder shanks are reconfigured from prior art to provide increased holding power between the bit holder shank and base block bore.

Abstract: An improved base block is disclosed for use mainly in road milling equipment, but also capable of use in trenching equipment and mining equipment. The base mounting portion is shortened in length from such prior art base blocks and has a reduced length device receiving portion extending therefrom that includes a bore therethrough. Rearwardly of the device receiving portion, the base mounting portion includes a reduced diameter semi-bore or curved wall capable of engaging a portion of the shank side wall of a standard length bit/holder shank. Additionally, an angled slot adjacent the rear of the device receiving bore increases access to the rear to aid removal of a bit/holder therefrom.

Abstract: The invention relates to a bit holder for an earth working machine, in particular a road milling machine, that comprises a bit receptacle in the region of a working side of a support member and that indirectly or directly carries an insertion projection on an insertion projection side of the support member, the support member comprising two stripping surfaces [first or second stripping surfaces] that form a stripping surface pair and are at an angle to one another. In order to achieve a stable and long-lived configuration with such a bit holder, provision is made according to the present invention that the support member comprises at least one further stripping surface that is at an angle to the two stripping surfaces of the stripping surface pair.

Abstract: A cutter head for a mining machine includes a first end and a second end with a drum axis extending between the first and the second ends. The cutter head also includes a web coupled to the second end of the drum. The web includes a plurality of arcuate apertures. Each arcuate aperture extends through an angle about the drum axis. The cutter head further includes a plurality of first ribs coupled to the web. Each of the first ribs is positioned between adjacent arcuate apertures. The cutter head also includes a plurality of second ribs coupled to the web. Each of the second ribs extend across one of the plurality of arcuate apertures. A first angle that extends between one of the first ribs and an adjacent one of the second ribs is different than a second angle extending between the one first rib and another adjacent second rib.

Abstract: A body of a degradation pick may comprise a substantially conical frustum. A hammer element may be integrally formed with the substantially conical frustum and extend there from in one radial direction. A shank may protrude from the body opposite a narrow end of the substantially conical frustum.

Abstract: A replaceable arbor tool holder for replaceable impact tools provides a base structurally carrying a tool holder for a replaceable impact tool. The base is arcuate and the tool holder is structurally interconnected to a top surface of the base. A medial channel is defined in the tool holder to releasably carry an impact tool. The tool holder converts impact forces upon the impact tool into frictional forces along a line tangent to the circumference of the arbor when the tool holder is fastened to the rotating arbor.

Abstract: A tool for mounting a chisel on a chisel holder, having an actuating member, which has a push-off section, wherein the actuating member can be displaced along a displacement direction. It is possible to simplify changing the chisel if the actuating member can be shifted by an actuating unit. The actuating unit has a draw-in section, which is spaced apart from the push-off section and is arranged transversely with respect to the displacement direction of the actuating member. The actuating member can be power-operated bidirectionally in the displacement direction by the actuating unit.

Abstract: A pick assembly (100) comprising a pick tool (200), a pick holder (300) and a rotatable drive means (400); in which the pick holder is attached to the rotatable drive means and the pick tool comprises a base (220) and a strike element (210) capable of being attached to the base, the strike element comprising a strike tip (212) defining a strike tip axis (213) and the base capable of being attached to the pick holder; the pick holder and pick tool being configured in relation to the drive means operative to the strike tip axis being oriented to within a strike angle of at most 5 degrees with a strike plane on which the strike tip will travel when driven by the drive means.

Abstract: A tool holder is disclosed for use with a milling drum. The tool holder may have a generally cylindrical body defining a first end configured to be received within a tool mounting block of the milling drum, and a second end configured to receive a cutting bit. The tool holder may also have a flange located between the first end and the second end, and a first blind bore initiating at the second end and stopping at the flange such that the generally cylindrical body is substantially solid at the flange. The tool holder may further have at least one sloped surface located at a side of the flange facing the first end of the generally cylindrical body.

Abstract: The present invention relates to a composite tool comprising at least two milling tool holders, to a milling tool holder for such a composite tool and to a milling drum equipped with such milling tool holders. According to the present invention, a milling tool holder is utilized for supporting a tool replacement device during tool replacement of the milling tool in the milling tool holder that precedes it in the peripheral direction. To this end, according to the present invention, a supporting area is provided on the base element of the milling tool holder, which supporting area provides appropriate stabilized guidance for the tool replacement device.

Abstract: A cutting tool mounting assembly adapted for attachment to a surface of a rotatable driving member of a cutting tool machine. The cutting tool mounting assembly includes a tool holder having a key shank, a base attached to the surface of the rotatable driving member with the base having a mounting groove for receiving the key shank of the tool holder, and a resilient retention structure configured to interact with the base and the tool holder to facilitate a friction fit between the tool holder and the base.

Abstract: The invention relates to a bit holder having an insertion projection and having a holding projection having a bit receptacle, the insertion projection comprising a bearing segment and the holding projection comprising a supporting segment. In order to allow the bit holder to be braced in permanent and stable fashion with respect to a base part, provision is made according to the present invention that the supporting segment and/or the bearing segment comprise two supporting surfaces and bearing surfaces, respectively, arranged at an angle to one another; and that the longitudinal center axis of the bit receptacle and the longitudinal axis of the insertion projection enclose an obtuse angle.

Abstract: The invention relates to a bit holder having an insertion projection and having a holding projection, the holding projection comprising a bit receptacle, and the holding projection protruding at least locally from or beyond the insertion projection in the tool feed direction. A bit holder of this kind is designed in service-life-optimized fashion by the fact that the holding projection comprises a supporting segment having a rigid, shaped-on supporting surface that is arranged at least locally in front of the insertion projection in the feed direction. The invention further relates to a base part for receiving an aforementioned bit holder.

Abstract: A cutting tool holding device includes a base, a cutting tool holder and a fastening member. The base includes an abutting portion and a transverse dovetail groove, wherein the abutting portion is defined between a first wall with a mounting surface and a second wall, and the transverse dovetail groove is formed on the mounting surface. The cutting tool holder has a transverse dovetail portion, wherein the cutting tool holder is abutted against the abutting portion, and the transverse dovetail portion is detachably engaged into the transverse dovetail groove on the mounting surface of the second wall. The fastening member is for fastening the cutting tool holder to the base.

Abstract: A plurality of differing horizontal pairs of slot shapes are positioned in the upper body portion of a quick change type bit holder to provide access to a bit extractor tool for removing the bit holder from its associated bit block.

Abstract: A bit holder for use in a bit assembly in road milling, mining and trenching equipment has a hollow generally cylindrical shank and first and second elongate slots positioned in spaced axial relation through the shank. The first slot extends along the shank to the distal end thereof. The second slot may be altered in length and/or shaped to fine tune the outward radial force the shank exerts against the bore of a bit holder block into which it is inserted.

Abstract: A base block for a cutting drum is disclosed. The base block may have a first end. The first end may have an opening configured to receive a tool. The first end may also have a flat surface surrounding the opening. The base block may have a second end configured to abut the cutting drum. The base block may further have an internal passageway commencing at the opening configured to receive the tool. The passageway may define a longitudinal axis that is offset by an acute angle from being perpendicular to the flat surface.

Abstract: A quick change type bit holder for use in a bit assembly for road milling, road planing, trenching and mining equipment wherein a bit shank extends completely through an axially oriented bit holder bore includes a slotted shank having an outwardly tapered bit holder bore wherein insertion of the bit shank in a bit block acts to slightly collapse the shank which collapses the tapered bore to a generally cylindrical configuration that preferably snugly retains the bit shank rotatably therein.

Abstract: A cutting bit retention assembly (399) that includes a cutting bit holder (500), which receives a cutting bit (58) and has shank (504) that extends into a bore (418) in a support (400). The shank section (504) of the cutting bit holder (500) presents a surface (530) defined by a notch (528) that selectively cooperates with a retention pin (670). A transverse bore (430) in the support (400) carries the retention pin (670). The retention pin (670) is selectively movable to any one of several positions. One position is a non-retaining position wherein the retention pin (670) does not engage the notch surface (530). Another position is a retaining position in which the retention pin (670) engages the notch surface (530) to urge the cutting bit holder into the cutting bit holder bore (418). Still another position is an ejecting position in which the retention pin (670) engages the notch surface (530) to urge the cutting bit holder (500) out of the cutting bit holder bore (418).

Abstract: Retaining a cutting bit. At least some of the illustrative embodiments are methods including: placing a neck portion of a retaining clip in a groove on outer surface of a sleeve (the sleeve with a cylindrical bore defining a longitudinal axis); then telescoping the sleeve and retaining clip, with the neck portion placed in the groove, within a bit block (the telescoping such that an arm portion of the retaining clip partially occludes an aperture of the cylindrical bore); and then inserting a shank portion of a cutting bit within the cylindrical bore of the sleeve (the arm portion of the retaining clip mates with at least a portion of an annular groove of the shank portion); and retaining the shank portion of the cutting bit by way of the arm portion of the retaining clip.

Abstract: In one aspect of the present invention, a degradation assembly has a holder comprising a first end and a second end and a shank with a longitudinal central bore having an opening at an end proximate the second end. The shank portion of the holder has an inside diameter of the bore and an outside diameter wherein either the inner diameter or the outer diameter comprise at least one recess disposed therein which comprises a depth of less than the distance between the inner diameter and the outer diameters.

Abstract: A quick-change tool holder has an enlarged forward end, a rearwardly extending shank, and an axial bore extending through the enlarged forward end and the shank with the bore having a diameter sized to receive the shank of a cutting tool. A second blind hole extends into the side surface of the enlarged forward end. An extraction device, such as the shank of a worn tool, is inserted into the blind hole. Where the extraction device is a worn tool, the cutting end of the tool is hit with a hammer to remove the tool from a base block mounting.

Abstract: In one aspect of the invention, a holder assembly comprises a connection block having a block bore extending from a first opening proximate a first end of the assembly to a second opening proximate a second end of the assembly. The block is adapted for connection to a driving mechanism. An extension element is disposed in the block bore and protrudes from the first opening of the block bore. The extension element comprises a central extension bore having a longitudinal length. An attachment mechanism is disposed within the central extension bore of the extension element and is disposed proximate the second end of the assembly.

Abstract: In one aspect of the invention, a pick assembly comprises a pick shank press fitted within a bore of a pick holder. The pick comprises a pick head opposite the shank. The shank also comprises at least one longitudinal slot extending towards the pick head along the shank from a distal end of the shank. The slot allows the shank to resiliently collapse upon insertion into the bore while still allowing the shank to maintain a press fit while within the bore.

Abstract: A block and non-rotating wear sleeve for holding a cutting tool used with mining and construction is disclosed. A key is used to intersect with notches in the wear sleeve and block at a rear face of the wear sleeve and block to prevent rotational movement between the wear sleeve and block. Locating the key and notches at the rear face provides an easily manufactured anti-rotation means which is also sheltered from the most of the abrasion experienced by the block and wear sleeve.

Abstract: A tooth system for a tool for earth moving machinery that includes a holder located on the tool and a front tooth portion that is detachably arranged on and in relation to the holder, which tooth portion is in the form of a replaceable wear/replacement part with a rear leg and the holder embodies a cavity designed to receive the leg of the tooth portion. This achieves a unified joint for assimilation of occurring loads via a predetermined connection geometry embodying special, opposite, mutually interacting contact surfaces and clearance surfaces arranged along the tooth portion and holder. The joint includes a multi-armed, preferably cruciform, cross section comprising at least four projection arms and at least four grooves each that interact with each projecting arm. Each projection arms includes a vertically arranged, upper arm, lower heel and two, essentially horizontally and laterally arranged, wing portions, with a tensioning device.

Abstract: An improved bit assembly for road milling, mining, and trenching equipment includes a streamlined tip assembly that is a combination of conical and cylindrical in shape and devoid of protrusions or annular indentations that might impede the flow of removed material over and around the bit assembly or provide space for removed material to become clogged or imbedded on the tip assembly. The generally cylindrical hollow shank that mounts the bit holder to the bit block includes at least one axially aligned slot along its side wall that allows the side wall to bend supply radial force to maintain the bit holder in the bit block.

Abstract: A cutting tool holder-base assembly (399) has a base (400). The base (400) is adapted to attach to a surface (40) of a rotatable driving member (38). The tool holder-base assembly (399) includes a cutting tool holder (500) with head region (502) containing a cutting tool bore (506), and a shank region (504) with a distal end (524). The shank region (504) has an alignment notch (528) presenting an alignment surface (530) at the distal end (524). The assembly (399) further has a base (400), which contains a tool holder bore (418) and a transverse passage (430) intersecting the tool holder bore (418). There is an elongate pin (436) in the transverse passage (430). The elongate pin (436) has an exposed portion (440) thereof passing through the tool holder bore (418) wherein the cutting tool holder (500) is able to enter completely the tool holder bore (418) of the base (400) when the alignment surface (530) is in alignment with the exposed portion (440) of the elongate pin (436).

Abstract: In one aspect of the invention, a degradation assembly comprises an impact tip brazed to a carbide bolster. A stem protrudes from the bolster, being adapted to be retained within a bore connected to a driving mechanism. A locking fixture is disposed within the bore and locking the stem to a wall of the bore.

Abstract: A bit holder for use in a bit assembly in road milling, mining and trenching equipment has a hollow generally cylindrical shank and first and second elongate slots positioned in spaced axial relation through the shank. The first slot extends along the shank to the distal end thereof. The second slot may be altered in length and/or shape to fine tune the outward radial force the shank exerts against the bore of a bit block into which it is inserted.

Abstract: A chisel holder system including a base part and a chisel holder. The base part includes a socket wherein the chisel holder with a plug-in insert is introduced. The chisel holder has a bearing surface supported on a supporting surface of the base plate, and the base part has a shoulder connected to the supporting surface. A replacement chamber is formed between the shoulder and a facing end surface of the chisel holder. According to this invention, the supporting surface is placed in the transition region in relation to the shoulder by at least one recess of the shoulder so that the flat-shaped connection between the supporting surface and the shoulder, in the region of the recess, is interrupted in order to optimize the resistance to wear and tear of the base part.

Abstract: A stump grinding wheel includes a wheel disc, which includes multiple recesses formed about its periphery. A peripheral cutter assembly is disposed in each one of the recesses and is mounted on the wheel disc. Multiple side cutter assemblies are mounted on the wheel disc, and each one includes a first pocket and a second pocket. The first pocket is disposed on one side of the wheel disc and the second pocket is disposed on the other side of the wheel disc, and a wear pad is formed adjacent a selected end of each pocket. A cutting tooth is received in aligned openings formed in the first pocket, the wheel disc, and the second pocket. A nut threadably engages the cutting tooth of the side cutter assembly to secure the tooth to the first and second pockets, and to secure the pockets to the wheel disc.

Abstract: An assembly for mounting an excavating tooth particularly suited for a dredge cutterhead includes a base, an adapter, and a lock. The base includes a convex, curved bearing surface that abuts a concave, curved bearing surface on the adapter. The curved bearing surfaces are able to maintain substantially full contact with each other under transverse loading. The undersurface of the base is formed with a groove to improve the strength and durability of the weld.

Abstract: A tooth system (1) for a tool (2) for earth moving machinery (3) is disclosed, which tooth system is of the type embodying a holder (4) located on the tool and a front tooth portion (5) that is detachably arranged on and in relation to the holder, which tooth portion is in the form of a replaceable wear and/or replacement part designed for the actual earth moving (W) and embodies a rear leg and the holder embodies a cavity (14) designed to receive the leg in interaction with the tooth portion and thereby achieve a unified joint (A, B, C, D) for assimilation of occurring loads (Fs, Fc, Fp) via a predetermined connection geometry embodying special, opposite, mutually interacting contact surfaces (15) and, at least initially, clearance surfaces (16) that are arranged along the tooth portion and holder.

Abstract: A bit holder for use in a bit assembly in road milling, mining and trenching equipment has a hollow generally cylindrical shank and first and second elongate slots positioned in spaced axial relation through the shank. The first slot extends along the shank to the distal end thereof. The second slot may be altered in length and/or shape to fine tune the outward radial force the shank exerts against the bore of a bit block into which it is inserted.

Abstract: A block and non-rotating wear sleeve for holding a cutting tool used with mining and construction is disclosed. A key is used to intersect with notches in the wear sleeve and block at a rear face of the wear sleeve and block to prevent rotational movement between the wear sleeve and block. Locating the key and notches at the rear face provides an easily manufactured anti-rotation means which is also sheltered from the most of the abrasion experienced by the block and wear sleeve.

Abstract: A universal digging tooth attachment apparatus adapted to be secured to a forward edge of a bucket lip of an earth moving implement. The universal digging tooth attachment has a first element with an elongate section defining a first generally planar surface for abutting and engaging along the length thereof with one face of the bucket lip of the earth moving implement and a second element. The second element has an elongate section defining a second generally planar surface for abutting and engaging along the length thereof with the bucket lip of the earth moving implement directly opposite from the elongate section of the first element. One of the first and second elements has an earth engaging tooth projecting therefrom. A slip joint operably connects the first and second elements to each other to allow for adjustment of a distance between the first and second planar surfaces to accommodate attachment of the digging tooth to implements having bucket lips of differing thicknesses.

Abstract: A chisel holder system including a base part and a chisel holder. The base part includes a socket wherein the chisel holder with a plug-in insert is introduced. The chisel holder has a bearing surface supported on a supporting surface of the base plate, and the base part has a shoulder connected to the supporting surface. A replacement chamber is formed between the shoulder and a facing end surface of the chisel holder. According to this invention, the supporting surface is placed in the transition region in relation to the shoulder by at least one recess of the shoulder so that the flat-shaped connection between the supporting surface and the shoulder, in the region of the recess, is interrupted in order to optimize the resistance to wear and tear of the base part.

Abstract: Cutting tool assemblies and retention sleeves. The assemblies may include a support member that has a sleeve-receiving hole therethrough and a cutting tool that has an elongated shank. Various configurations of sleeve segments are disclosed for non-rotatably supporting the elongated shank of the cutting bit in the support member. Such sleeve segment embodiments may be provided with a plurality of axially extending notches to establish segments of various degrees of interference fit between the sleeve and the support member when seated in the sleeve-receiving hole of the support member.

Abstract: A tool holder including a tool box with a tool seat in a holding projection for receiving a tool in such a manner that it can be replaced. The tool seat is configured as a bore and has a tool insertion opening. The tool holder has a fastening side with a fastening projection and, facing away from said fastening side, an exterior, and during use of the tool centrifugal forces are effective in the direction from the fastening side to the exterior. This invention ensures the free rotatability of a tool inserted in the tool holder even if overburden material enters the tool seat. For this purpose, the holding projection has an opening penetrating the inner wall of the tool seat and creating a spatial connection to the exterior, and the opening opens the tool seat towards the exterior.

Abstract: A circular-shank tool including a tool holder for improving the centering of the shank of the circular-shank tool in the locking sleeve by a configuration of the retaining elements and to improve an ability of the shank to rotate in the sleeve. To achieve this, the retaining elements are distributed between two stamped edges that lie transversely with respect to a longitudinal axis of the locking sleeve and are stamped inwards or indented, the stamped edges extend over part of the circumference of the locking sleeve and are interspaced at a distance that corresponds to the width of the peripheral groove in the shank of the circular-shank tool and the retaining elements form a coaxial concave centering section facing the convex groove base of the peripheral groove.

Abstract: A pedestal assembly for an asphalt cutter and/or a longwall shearer includes a cutting bit detachably secured in a tool body mounted within a block with the block fixedly secured to a pedestal. The first end of the pedestal has a recess to overlap the second end of an adjacent pedestal when the pedestals are mounted on the outer surface of a drum of the cutter. The first end of the pedestal further includes a lateral flat surface portion for deflecting material made loose by the cutting bit.

Abstract: A tool holding device is disclosed, and the tool holding device includes a base, a block, and a fastening member for securing the block. The base includes a receiving portion defined between a countering wall and a shoulder wall, a surface defined adjacent to the shoulder wall perpendicularly and away from the countering wall, a penetrated hole defined on the countering wall, and a positioning hole communicating with the penetrated hole. The block includes a holding portion held in the receiving portion, a handle received in the penetrated hole, and a holding hole for holding a chisel. The countering wall and the shoulder wall define an angle less than or equal to 90 degrees. Therefore, the counterforce bearing of the base and block are both enhanced to raise the strength of the tool holding device.

Abstract: A cutting element assembly for use on a rotary drill bit for forming a borehole in a subterranean formation. A cutting element includes a substrate having a base member affixed to a back surface of the substrate is disclosed, wherein the base member includes a recess configured to secure the base member to a rotary drill bit. An inner member may be positioned within the recess of the base member. Also, a structural element may be coupled to the inner member or to the base member. A rotary drill bit may include a cutting element assembly. In addition, a method of securing a cutting element to a rotary drill bit may include providing a base member affixed to a cutting element and positioning the base member within a recess of the rotary drill bit.

Abstract: A rock breaking device employs a falling weight and a striker pin or other tool held within a tool holding structure supported by a recoil assembly includes a number of isolator structures that protect the rock breaking device by absorbing excess forces that may be applied to the recoil assembly. Each isolator structure includes a front plate that extends below a lower side of a recoil tube flange. In new rock breaking devices, the front plates may be incorporated as part of the isolator structures. Alternatively, an existing rock breaking device can be retrofitted by welding a heavy plate onto the front of an existing front plate of the isolator structures. The heavy plate extends beyond the lower side of the recoil tube flange to provide greater strength.

Abstract: A mineral cutter system comprises a pick box (3) adapted to be secured, by welding, to a powered drum or disc (2) and having a bore (4) to receive a replaceable sleeve (5) having a collar (8) and also a circular section bore (15) to receive a circular section shank (16A or 16B) of a replaceable mineral cutter pick (17A or 17B), the bore (4) of the pick box (3) incorporating at least one flat (6), and the sleeve (5) being provided with at least one external flat (7) to engage the flat (6) whereby the sleeve (5) is non-rotatable with respect to the box (3), and the collar (8) of the sleeve (5) being both recessed (at 21) to accommodate a circular collar (20) of a point attack pick (17A), and slotted to provide opposed abutment faces (23) to engage a pair of opposed flats (27) of a non-rotatable, semi-forward attack pick (17B). The invention also includes a rotary drum or disc (1) provided with this cutter system and with either a rotatable or non-rotatable pick (17A or 17B).

Abstract: A tool holder including a tool box with a tool seat in a holding projection for receiving a tool in such a manner that it can be replaced. The tool seat is configured as a bore and has a tool insertion opening. The tool holder has a fastening side with a fastening projection and, facing away from said fastening side, an exterior, and during use of the tool centrifugal forces are effective in the direction from the fastening side to the exterior. This invention ensures the free rotatability of a tool inserted in the tool holder even if overburden material enters the tool seat. For this purpose, the holding projection has an opening penetrating the inner wall of the tool seat and creating a spatial connection to the exterior, and the opening opens the tool seat towards the exterior.