Arrangement for tools for restricted spaces

Abstract: Provided at the end part of the shaft is a seat, which permits the positioning of and a stable support for a cutter in at least two of the principal directions utilized in the machining operation, so that the stresses imposed on the cutter during such machining are transferred in an effective fashion to the shaft. A novel feature is the arrangement on the shaft of at least one tightenable fastening device which, after tightening, engages with the cutter and forces it against at least one surface on the seat, and the arrangement on the cutter of stop parts with which the fastening devices is intended to engage only once the cutter, after displacement relative to the seat on the shaft and whilst still remaining in contact with it, has reached its operating position.

Description: Technical field The invention relates to a tool arrangement for cutting machining operations, according to the preamble of claim 1 and as known from US-A-4102591. Tools intended for operations of this kind are previously disclosed, and as a general rule comprise a cutter of hard metal, carbide material or similar attached by means of a threaded connection to the end of a shaft or similar capable of being inserted into the hole or the tube, in which case the arrangement is such that, in order to remove a worn cutter or in order to fit a new one, it is necessary fully to unscrew a screw passing through the cutter before the cutter can be removed or attached. The fact that it is necessary to keep track not only of the cutter, which in many cases is very small, but also of a loose screw, and to fit the latter into a threaded hole in the shaft, makes the operation difficult, in addition to which there is always the risk of using a cutter for an excessive period in order to avoid having to change the cutter. US-A-4102591 reveals a cutting tool including a holder with an end face intended to support an insert. The end face is provided with surface portions adapted to hold the insert in a defined predetermined position once a screw passing through a hole in the insert is threaded into a threaded hole at the end portion of the holder body. The known cutting tool is an example of the type mentioned above, where, in order to replace a worn insert, the screw must be completely withdrawn, the worn insert removed, a new insert applied at the end of the holder and the screw inserted through the hole of the insert, aligned with the threaded hole at the holder and tightened. Another example of known art is revealed in US-A-2924129 but in that example it is necessary not only to remove and manipulate a screw but also a retainer means interposed between the screw head and an insert or bit and adapted to clamp the insert or bit against an end face of a holder body. The screw is arranged to press the retainer against the insert or bit and thereby press the latter against a seat at the end of a holder means on tightening of the screw engaging a threaded bore at the holder body. Object of the invention The object of the invention is to make available an improved arrangement which, at the same time as it provides a secure grip, also facilitates the replacement of cutters to a considerable degree, in conjunction with which no handling of loose components, apart from the cutter itself, is called for. Description of the invention The idea behind the invention is the provision at the end part of the shaft of a seat, which provides positioning of, and a stable support for a cutter in at least two of the principal directions utilized in the machining operation, so that the stresses imposed on the cutter during such machining are transferred in an effective fashion to the shaft, the arrangement on the shaft of at least one tightenable fastening device which, on tightening, engages with the cutter and forces opposing surfaces on the seat, and the arrangement on the cutter of holder and the cutter to interact in a stabilizing way a positioning means to be engaged by the fastening device in its holding position and allowing displacement of the cutter relative to the holder seat whilst still remaining in contact therewith. Description of illustrative embodiments The invention is described in more detail below with reference to the accompanying drawing, in which: Fig. 1 shows an embodiment of a cutter viewed from the side facing towards the shaft; Fig. 2 shows the cutter in accordance with Fig. 1 viewed from the side on which the cutting edge projects; Fig. 3 shows the cutter in accordance with Fig. 1 viewed from the outward-facing side; Fig. 4 is a section taken along the line A-A in Fig. 1; and Fig. 5 is a section taken along the line B-B in Fig. 3. The embodiment in accordance with Figs. 1-5 can be used for the machining of holes and similar with a diameter only slightly exceeding the diameter of the shaft of the tool holder. The cutter in accordance with Figs. 1-5, which is generally designated by 32, consists of an essentially circular main part 33 and an axially displaced essentially radially extending projection 34, which supports the cutting edge 35. The side 36 facing outwards from the shaft designated by 31 exhibits a through hole with an essentially round large hole part 37 situated eccentrically or in a radially offset fashion away from the side with the projection 34, and overlapping a smaller central hole part 38 together forming a common opening. The centrally situated hole part having a smaller diameter or area than the former hole, is surrounded by a countersunk surface 39 arranged concentrically around it, and extending as far as the edge of the first hole part 37. The countersunk part forms a step-like edge around the centrally situated hole part 38. The side of the cutter 32 facing towards the supporting holder shaft, which can be appreciated most clearly from Figs. 1, 2, 4 and 5, exhibits an inner plane surface 40, which encloses the major proportion of the central hole part 38 and in so doing terminates at the further hole part 37. Situated radially outside the inner central surface 40 is a conically tapered surface 41 with a outwardly top angle of say the order of 140°, which is partly intersected by the larger hole part 37. A heel 42, the outward-facing side of which lies in the same plane as the inner plane central surface 40, extends radially over the inclined surface 41 in the direction of the edge projection 34, 35. The heel thus exhibits essentially parallel triangular lateral surfaces. The end part of the supporting holder shaft for the cutter 32 is shaped in a complementary fashion and has a central threaded bore 43 surrounded by an inner plane annular surface 44, and an outer inclined surface 45. The inclined surface 45 is interrupted by a radial groove 46 with an outwardly increasing depth adapted to the shape or size of the heel 42. When fitting a cutter 32 to the supporting holder shaft, a screw threaded into the axial threaded bore 43 and having a head must be unscrewed for a sufficient distance to permit the screw head to be introduced through the larger hole part 37, i.e. with the cutter in a laterally displaced position. The cutter is then centred on the end of the supporting shaft by making the central hole part 38 engage the shank of the screw, simultaneously as the heel 42 is fitted into the groove 46, which positions the cutter in such a way as to prevent it from rotating about its centre. Once the cutter has reached the indicated position, the screw 47 is tightened. Removal takes place in the reverse sequence. The interaction between the plane and conical surfaces and the rotational stabilization by means of the heel 42 and groove 46 mean that the cutter is fixed in a stable fashion, and that the desired distribution of forces is obtained.

Claims: Tool arrangement for cutting machining operations , in particular milling, in restricted spaces such as internally in holes and inside hollow work pieces, including a milling cutter holder shaft (31) and a holed milling cutter insert (32) to be attached to a free end of the holder shaft (31), the free end of the holder shaft (31) being provided with a threaded bore (43) and adjoining positioning surface portions (44, 45, 46), the side of the insert facing the holder end face also being provided with positioning surface portions (40, 41, 42) arranged to co-operate with the positioning surface portions (44, 45, 46) of the holder end face, the insert having a holed base portion, the hole thereof allowing a shank portion of a threaded screw device co-operating with the threaded bore of the holder shaft to pass through and at the outer end of the hole a hole adjoining surface portion (39) serving as an abutment for a head of the screw device, the insert further having a projection (34), extending essentially radially beyond the outer extension of the insert, the extreme tip (35) of the projection forming the cutting edge, characterized in, that the positioning surface portions (40-42, 44-46) at the holder shaft (31) end face and the side of the insert (32) facing said end face each include a conical inclined surface (45, 41), the one concave, the other convex, that the hole (38) of the insert (32) adapted to the screw device shank opens up into a radially offset, wide hole portion (37), the dimension of which being adapted to the size of the screw head, and allowing the insert (32), in a radially displaced position, to be passed over the head of the loosened screw device on being moved towards or from its working position at the holder shaft end face (44, 45), and that the co-operating conical opposite inclined surfaces (41, 45), on tightening of the screw device, are adapted to align the insert (32) and the hole portion (38) adapted to the screw shank to said screw shank received in the threaded bore (43). Arrangement according to claim 1, characterized in that the positioning surface portions at the insert and the holder end face also include an inner essentially, radial and flat surface (44, 40) adjacent the threaded bore (43) for the threaded screw device at the holder shaft (31) and the hole (38) at the insert (32), respectively. Arrangement according to claim 1 or 2, characterized in that at the holder end face and insert face, respectively, an essentially radially extending groove (46) intersects the concave one of the opposed surfaces, and that a complementary essentially radially extending heel (42) protrudes from the convex one, the heel (42) to be received in the groove (46) for interlocking the holder shaft (31) and the cutter insert (32) against relative rotation. Arrangement according to claim 1, characterized in, that the abutment surface (39) at the side of the cutter insert (32) facing away from the holder shaft (31) end is countersunk so that the head of the screw device engaging same is below the outwardly facing cutter insert end side.

Inventors: MIHIC WLAJKO, MIHIC, WLAJKO
Applicants: MIRCONA AB
Application year: 1992
Main classification: B23B27
IPC codes: B23B27