Jig for grinding sharp-edged tools

Abstract: Jig for grinding sharp-edged tools. The jig consists of a housing (1) in the form of a casing designed with a passage running through it whose at least one end (10) is flat, plus a seat (2), also in the form of a casing designed with a passage running through it, located in the passage of the housing and lockable (6) in this housing in an inclined position in relation to the passage in the housing, whereby the seat (2) is provided with a clamping device (4) for firmly holding a tool that is to be ground so that it extends through the passage of the seat, and that the seat (2) has such a length that one end of it extends out beyond the housing at the flat end (10) of the housing.

Description: The present invention concerns a jig for grinding sharp-edged tools such as chisels, gouges, parting tools, etc. US 467 857 describes a stationary tool grinder incorporating a jig according to the preamble of claim 1 in which a tool to be ground is fastened and adjusted angularly towards the grinder in a multitude of ways depending on the kind of grinding desired and the kind of tool to be ground. A tool is fastened with three screws in a hollow block protruding through a housing of the jig. Both the block and housing can be angularly adjusted separately and locked towards the grinder for a desired positioning and angle of the tool to be ground. A separate centering device, pivotally arranged on the grinder, is used together with adjustment of the screws for ensuring a symmetrical positioning of the tool in the block. The housing can then also be rotated for grinding on the other side of the tool keeping the initial settings. The invention makes it possible to even grind bevelled chisels with an oval cross-section, which are normally very difficult to grind with precision, as the convex underside of the chisels cannot rest against the grinding support in an exact and stable manner. With the help of the invention, the oblique angles of the tool are adjustable in a continuously variable manner for grinding. These opportunities for grinding sharp-edged tools are possible through the invention having the characteristics specified in claim 1. A jig with such an extensive range of functions is not previously known. The invention will be described in the form of examples with reference to the drawings, where Fig. 1 shows the jig according to the invention including the housing with the casing for firmly holding chisels with an oval cross-section, Fig. 2 shows an open V-shaped seat for grinding tools with straight lips, Fig. 3 shows a firmly clamped gouge, Fig. 4 shows the seat included in the invention in perspective, Figs. 5 and 6 show the invention used for grinding a bevelled chisel with an oval cross-section, Figs. 7 and 8 show the grinding of a gouge with a straight lip and with the use of the open seat, Figs. 9, 10 and 11 show the invention used for grinding a curved or cam-shaped lip, Fig. 12 shows an angle marking on the casing and Fig. 13 shows an angle marking that can be used when adjusting the inclination of the lip of the tool. Fig. 1 shows an end view of the jig according to the invention, which includes a housing 1 essentially rectangular in cross-section. Housing 1 accommodates a similarly rectangular in cross-section enclosed seat 2, one short side of which is provided with a notch 3. The side opposite the said short side of seat 2 has a screw 4 running all the way through it and threaded in the seat whose inner end is provided with a counterstay 5 that has a notch. The seat 2 can be removed from the housing 1 but can also be locked in place in the housing with the help of a locking screw 6. The treads of the locking screw 6 grip with equivalent threads in a hole 7 (Fig. 4) in the seat and press against the flat inside 8 of housing 1 when locking screw 6 is tightened. The tool 9 is inserted into the seat and is placed with the edges running in notch 3 and the notch of the counterstay 5 and locked in the seat with the help of screw 4. In the situation shown, the seat 2 and thus the tool 9 extend at right angles out from at least the one flat end 10 of the housing. This right-angled position can be taken up automatically by the seat 2 pressing against a shoulder 11 in the passage of the housing 1 when the locking screw 6 is turned around its centre. By loosening the seat 2 from the housing using the locking screw 6, the seat can be turned to the angled position required and once again locked against the housing 1 with the help of the locking screw 6. As is evident from the following, seat 2 extends somewhat outwards from the flat end 10 of the housing 1. Figs. 2 and 3 show an open seat 2'. Like enclosed seat 2, open seat 2' can be turned and locked in position against the flat inside 8 of housing 1. As is evident from Figs 2 and 3, open seat 2' has a flattened V-shape. A screw 12 threaded forwards and backwards in housing 1 is directed at the point of the V, i.e. the bottom of the open channel. By using this open seat 2', it is possible to grind tools such as gouges 13 or parting tools 14 or chisels or similar. As the free end of screw 12 ends in a point this is located co-axially with locking screw 6, it is possible to pivot the seat 2' with the tool in relation to the housing 1. Fig. 4 shows the enclosed seat 2 with a threaded hole 16 for screw 4 and, as previously mentioned, the threaded hole 7 for locking screw 6. Figs. 5 and 6 show the grinding of a bevelled chisel with the help of the invention. In the figures, 17 designates a grinding wheel and 18 a so-called universal support which is attached to the base of the grinding wheel and as such is fixed in relation to the rotating grinding wheel. Tool 9 is clamped firmly in housing 1 via seat 2 as described previously and, with the help of the latter, an oblique adjustment of the tool in relation to the housing is set, where the oblique adjustment determines the inclination of the cutting edge. The cutting angle of the tool is determined by displacement of the universal support 18 as indicated by the arrows P 1 (Fig. 5). During grinding, the flat and broad end 10 of the housing 1 abuts the universal joint 18 while the jig rests against the support 18 with the "underside" of seat 2, i.e. by being held with the end 10 pressed against the universal support 18, the housing guides the tool the whole time in a straight line movement, see arrows P 2 (Fig. 6). To grind the lip on the other side of the tool 9, the whole jig is turned 180°. The tool is held completely symmetrically in seat 2, i.e. at the same distance from both broad ends of the seat, which means that repeating the adjustment for grinding the other side of the lip is not necessary. Figs. 7 and 8 show the grinding of a gouge. In this case, seat 2' is used, which as is evident from the figures, does not extend outwards from the flat end 10 of housing 1. The gouge is clamped firmly as is shown in Fig. 3. As before, the flat end 10 of the housing 1 is supported against the universal support 18 during grinding, while the underside of the gouge abuts the support 18. During grinding, housing 1 thus guides the direction of the tool 13 towards the grinding wheel 17 while the underside of the gouge makes it possible to tilt the gouge during grinding to thereby grind the whole lip (compare the arrows P3 in Fig. 8. As was mentioned earlier in connection with Figs. 5 and 6, the angle of cutting is adjusted by displacement of the universal support 18 (arrow P 1 ). Figs. 9 - 11 show how it is possible to grind a lip with a curved or cam-shape with the help of the invention. The tool 9 is clamped firmly in the jig in seat 2 and the starting point is, for example, that shown in Fig. 9. By pivoting the jig against the support 18 around the lefthand edge of the housing at the same time as the jig is displaced with the seat 2 resting against support 18, as in the shown example, the originally straight lip will be ground to a curved shape. By turning the jig with the tool and performing the same movement but in a reverse direction, the other side of the lip of the tool can also be ground. Fig. 12 shows the seat 2 provided with a graduated scale up to 40°, whereby the symbol with the obliquely ground end of a tool and the angle marking δ explain the meaning of the scale. Fig. 13 shows more clearly the seat 2 located in housing 1. As is shown in the figures, housing 1 is shaped with a narrow side inclined "backwards", i.e. in a direction towards the operator when handling the jig. The design is conditioned by giving the seat sufficient free-play when being pivoted as well as keeping the housing as small and easy to handle as possible.

Claims: Jig to be guided by a support (18) on a grinding wheel for grinding a bevelled chisel tool, consisting of a housing (1) in the form of a casing designed with a passage running through it whose at least one end (10) is flat, plus a seat (2), also in the form of a casing designed with a passage running through it, located in the passage of the housing (1) and lockable (6) in this housing in an inclined position in relation to the passage in the housing , the seat (2) having such a length that one end of it extends out beyond the housing (1) at its flat end (10), the passage of the seat (2) having a rectangular cross-section whose one short side supports a screw (4) threaded in the seat whereby a tool (9) to be ground is symmetrically clamped in the seat (2) at the same distance from both broad ends of the seat with the help of the screw (4) so that the tool (9) extends through the passage of the seat, wherein an oblique adjustment of the tool (9) with seat (2) is settable in relation to the housing (1) for determining an inclination of a cutting edge, characterised in that one short side of the seat (2) is provided with a notch and the screw (4) is provided with a counterstay (5) with a notch, the tool (9) being clamped with it's edges running in the respective notches, and in that the jig is held with the flat and broad end (10) of the housing (1) pressed against the support (18) for guiding the tool (9) in a straight line movement during said grinding. Jig according to claim 1 characterised in that the passage of the housing (1) has a rectangular cross-section and that the seat (2) can be locked against one long side of the passage as seen in cross-section. Jig according to claims 1-2 characterised in that the clamped tool (9) extends along the mid-line of the seat (2) when seen at right angles to the direction of the clamping. Method for grinding a bevelled chisel tool on a grinding wheel, with a jig according to claim 1, characterised in that a cutting angle of the tool (9) is determined by displacement of the support (18), attached to the base of and in fixed relation to the rotating grinding wheel, so that during grinding, the flat and broad end (10) of the housing (1) abuts the support (18) while the jig rests against the support (18) with an underside of the seat (2), wherein the housing (1) guides the movement of the tool (9), and wherein the whole jig is turned 180° to grind a lip on the other side of the tool (9). Method according to claim 4 characterised in that the housing (1) guides the tool (9) in a straight line movement.

Inventors: JANSSON TORGNY, JANSSON, TORGNY, Jansson, Torgny Tormek AB
Applicants: TORMEK AB
Application year: 1999
Main classification: B24B3
IPC codes: B24B41, B24B3