Angle gauge for grinding sharp-edged tools

0001The present invention concerns an angle gauge used when grinding the lip of sharp-edged tools according to the introduction to claim 1.

0002It is of great importance that the lip of sharp-edged tools of various types, such as knives, chisels, etc., has the correct cutting angle in order for the tool to function in the correct way and with good control of its movement without the lip being damaged. The correct cutting angle naturally depends on the quality of the steel, the type of tool, the hardness of the wood and how hard one works with the tool. Experience of these variables determines the angle that is correct for each occasion.

0003A practical way of setting a certain cutting angle, chosen because of the reasons mentioned above, for grinding the tool has not been available. When grinding tools by hand today, there is only one type of template provided with notches or angular-shaped grooves of different angles in which the lip of the tool can be inserted to determine or estimate the cutting angle.

0004With the help of the invention, as is evident from the characteristics sections of the claims, an angle gauge has been devised with which it is possible to rig the tool at the grinding wheel and its holder for grinding to the correct, chosen cutting angle, and with which it is possible to even measure cutting angles found on the tool. With the help of the invention, the adjustment of the tool at the grinding wheel holder to attain the correct cutting angle can be made independent of the diameter of the grinding wheel within, of course, reasonable limits.

0005The invention will be described in greater detail with reference to the drawings where <b>Fig. 1</b> shows the angle gauge according to the invention seen from the side, <b>Fig. 2</b> shows a tool rigged for grinding with a certain diameter of grinding wheel and <b>Fig. 3</b> shows a situation equivalent to that shown in <u>Fig.</u> 2 but with a different diameter of grinding wheel. <b>Fig. 4</b> shows the set-up during the grinding of a gouge.

0006The angle gauge according to the invention includes a frame 1 with a certain longitudinal extension and a thickness of 3-5 millimetres, for example. At one end of the frame, a first device in the form of a cam plate 2 is arranged. Cam plate 2 is arranged to rotate around point 3 on the frame 1. In addition, cam plate 2 is provided with a slot 4 with its centre of curvature at 3. A locking screw 5 extends through the slot 4, with whose help the cam plate can be locked in position against the frame 1 at different angles of rotation. The edge of the frame 1, which is pointed towards the grinding wheel when the invention is in use, is convex and the cam plate 2 extends out from this edge 6 of the frame 1. A second device in the form of an elongated body 7 is arranged at the other end of the frame 1. The elongated body 7 is arranged to be rotatable and attached to the frame 1 around point 8. Body 7 also has a slot 9 with its centre of curvature at 8. A locking screw 10 extends through the slot 8, with whose help the elongated body 7 can be locked in position against the frame 1 at different angles of rotation. The elongated body 7 extends out from the edge 6 of frame 1 and has a flat edge 11 at its outer end.

0007In the example shown in Fig. 1, the cam plate 2 and the elongated body 7 are provided with sharp indicating points 12 and 13 respectively and the frame is provided with scales 14 and 15 respectively. Scale 14 for cam plate 2 is graduated from 150 to 250 millimetres and refers to the diameter of the grinding wheel in question. Scale 15 gives the intended cutting angle.

0008In addition, frame 1 is provided with a number of sharp pointed notches 16 with different bottom angles for easy checking of the cutting angle of a tool.

0009Fig. 2 thus shows the grinding of a steel tool 17 clamped in a jig 18 held by a universal support 19. The cam plate 2 is adjusted for grinding with a grinding wheel S with a diameter of 180 millimetres and the body 7 that determines the angle of the cutting angle that is to be ground is adjusted to 25°. Fig. 3 shows grinding with a 25° cutting angle but with a grinding wheel of 250 millimetres diameter.

0010Fig. 4 shows the equivalent grinding of a gouge 20 to an angle of 45° with a grinding wheel of 225 millimetres diameter. Here, the jig 18 is of another type than that shown in Figs. 2 and 3 and the gouge is tilted around its longitudinal axis during the grinding.

0011By allowing the possibility of always being able to compensate for the diameter of the grinding wheel with the help of cam plate 2, the correct cutting angle can always be set with the help of the device 7. The frame 1 with the devices 2 and 7 is brought to abut the grinding wheel S, as shown, with the diameter of the grinding wheel set on cam plate 2 and with the cutting angle set on body 7. The corner edge 21 (Fig. 1) of the flat edge 11 of this body that lies closest to cam plate 2 thereby abuts the grinding wheel S. The tool 17 (20) is now rigged in the grinding wheel support via the jig 18 so that its upper side coincides with the flat edge 11 in the manner shown in Figs. 2-4. Following this, the angle gauge is removed and the grinding begins. The cutting angle can be checked easily afterwards with the help of the pre-set angle gauge.

0012As is shown in the figures, the cam plate is provided with a window <u>22</u> in which a scale graduated in inches is visible.