GB2117288A - Machine for grinding of cutting tools - Google Patents

Abstract

A machine for grinding cutting tools X, particularly wood working cutters, is provided with a movable support 220 for the grinding wheel 700 so that its axis of rotation can be adjusted between horizontal and vertical positions. Two grinding wheels 700, are provided on the same shaft, one being a cup shaped grinding wheel. The movement of the table is controlled by engagement of a follower 800 with a template 900. <IMAGE>

Description

SPECIFICATION Machine for grinding of cutting tools The present invention is related to a machine for grinding of cutting tools, particularly woodworking cutters having tungsten carbide tips.

Cutters of this kind consist in general of a steel body and pieces of tungsten carbide which may be brazed onto the steel body with a silver alloy or bronze or they can be attached mechanically by clamping. The cutter body is usually of mild steel while the cutting material is hard metal for example sintered carbides or an alloy steel.

Standardized cutting tools are available as straight round cutters and cutters for certain sections and shapes which are common, for example tongue and groove in panelling, wood material with certain cross sectional shapes etc.

Cutters of this kind are manufactured in large series by tool makers and are stocked for sale.

Further, there are an indefinite number of dimensions and types of cutters having all shapes or profiles for use in the manufacture of different special products in wood, furniture, specially designed panellings etc. Cutters for this purpose must be ordered in each case and the number of cutting tips, diameter, cutting width, bore and shape will vary considerably in order to provide all the desired variations.

Certain details are, however, found on all types. The cutters have a chip angle, a cutting angle, a clearance angle, and a tip face (the face which in tangential direction decides the chip angle). The edge may be parallel with the center line of the cutter or can be an approximated helix turning right or left. The clearance face can in its other plane be parallel to the circular line or it can form an approximated helix to give clearance also in parts where the cutter is to work on a surface close to 900 on its centerline.

It should be evident that the possibilities of variations are numerous, but it is also to be pointed out that in spite of this the fact the different angles are rather constant. For cutters having tips of hard metal, a chip angle and clearance angle of 150 will be preferred. Different angles of edge in relation to the centerline of the cutter could however be varied to a certain extent to give the cutter the best possible cutting properties.

There are previously known a large number of machines for grinding of cutter tools as well as any other type of tools. The first to be mentioned is the universal tool grinding machine which, with a sufficient selection of special equipment can grind any type of cutters.

A universal tool grinding machine with sufficient extra equipment is, however, very expensive and adaptation and adjustment and correct use of the equipment is time consuming and requires a skilled tool maker.

For this reason it has been marketed different special machines for the manufacture of tools.

One type of machine is designed to grind only the tip phase which decides the chip angle and to decide the angle of the edge in relation to the center line of the cutter and perhaps the clearance angle on one particular tool. Other machines can only grind the shape and profile of the cutting tools.

The purpose of the present invention is to provide a machine for grinding of cutting tools, particularly for wood working and especially cutters having hard metal tips enabling a toolmaker to, with a minimum of additional equipment and a minimum of readjustment, can carry out all grinding operations required for the manufacture of a cutting. The machine provides for automatic correct adjustment of the chip angle and the clearance angle, i.e. the angle the machine is designed for which means 150 which is preferred for both angles.

The machine according to the invention is to be a complete unit for the operation required for grinding of a cutter can be carried out with simple and rapid adjustment without further equipment.

The invention is characterized by the features indicated in the claims, and will be explained more in detail in the following with reference to the drawings on which: Figures 1 and 2 are perspective views of the main components of the machine, seen from two sides, Figures 3-7 shows the support of the spindle with grinding wheels in different positions, and Figure 8 shows the working principle of the machine.

On Figures 1 and 2, the tool X, which is to be ground is positioned on a dividing head 401 on a table 301. The table can be moved freely on precision roller bearings in the two directions indicated by x and y. A template 900 having the profile to which the tool is to be ground is attached to the table 301 while a finger 800 having the same shape as the grinding wheel 700 controls the motion of the table. The table is moved in the x and y direction to follow a curve which depends on the shape of the template 900 and the finger 800. The grinding wheel which preferably is a diamond wheel will then grind the same shape in the tool X. This principle is used in many machines and is a simple way of copying directly. The main feature of the machine in accordance with the invention is that it can also grind other faces by adjustment of a housing 220 for the spindle.The spindle housing 220 can be adjusted to vertical position as shown in Figure 2 and shown diagrammatically on Figure 8 for cutters having a plain face and at an angle of more or less than 900 as shown on Figure 4 and 5 for oblique faces.

A dividing head is operated with the hand wheel 435 on the bracket 430 to a point which is found on a scale. This point indicates the diameter of the cutter to be ground. If the cutter diameter theoretically was equal to zero, the center line for the dividing head would be at the same level as the front of the diamond wheel 780 or 28.9 mm above the center line for the bracket 201 in the embodiment which is shown. If, for example, the average diameter of the cutter X is 100 mm, the dividing head will have to be moved 50 mm rearwardly and upwardly along the bracket 430.

Then the centerline of the dividing head will automatically be lifted as far as required to give the cutter a chip angle of 1 50. The motion of the table 301 in the y-direction must be locked by means of screws 330 and 331. Particularly, when face grinding cutters having oblique faces, the y-motion of the table 301 must be locked, with the table in a position at which the average thickness of the cutter is exactly in front of the diamond wheel.

The cutter is now attached to the rotor in the dividing head 401 with a tungsten carbide tip somewhat lower than the face of the diamond wheel. The table is then moved back and forth in the x direction and the cutter is rotated slowly with a hand wheel 450 until the diamond wheel 750 touches the tungsten carbide tip. The operation is continued when the diamond wheel grinds the tip but now with a motion of the table 301 in the x-direction for controlled adjustment of the grinding depth as indicated on the indicator 455 for each motion of the table. When the surface of the tungsten carbide tip is ground clean the scale on the indicator 455 is set at zero. With the hand wheel 450 the cutter is brought away from the diamond wheel 780. The table 301 is locked in rear position while the dividing mechanism is released with a button 440.The spindle in the dividing head together with the cutter is rotated with the hand wheel 408 until the next tungsten carbide is in position for grinding.

This operation is repeated by movement of the table 301 in the x-direction for adjustment of the grinding depth until the indicator again shows zero. The operation is continued on the next tungsten carbide tip on the cutter until all the tips have been ground. If one of the carbide tips is not ground clean because it is lower than the other tips, the grinding of same is continued by adjustment of the handwheel 405 beyond the zero point on the indicator. When this tip also is ground clean the indicator has to be readjusted to a new zero value and the other previously ground carbide tips has to be reground to the new zero value on the indicator 455. All faces of the tungsten carbide tips must have the same radius when the grinding is terminated.

During grinding of tungsten carbide with diamond wheels it is necessary to have a sufficient cooling with water and the machine is provided with its own water cooling system with a tank 101 and a circulation system. If the cutters are less than 25 mm wide both diamond wheels 700 and 780 can remain on the spindle (see Fig. 8) and in this case it is not necessary to remove or change diamond wheels for the next operation. If the cutters are wider than 25 mm it is necessary to remove the diamond wheel 780 for the following operation so that only the diamond wheel 700 is active. The mid portion of the diamond wheel 700 must always be located in front of the mid lie of the bracket 201.

The next operation is to grind the clearance angle. The spindle housing 220 has to be rotated to horizontal position. If the cutter does not require side clearance the spindle housing 220 is positioned at zero degrees as shown on figure 1 and 2. For side clearance the spindle housing 220 must be positioned at another angle. If side clearance is required on both sides of the cutter the grinding must be made in two stages.

The template 900 which is mentioned previously is attached to a holder 350. The finger 800 must have the same shape or profile as the diamond wheel 700 in use. Motion of the table 301 in the y-direction must be released so that the table can move in the x-direction and the y-direction. The hand wheel 535 will adjust the finger 800 to correct position sideways and this also controls the different motions so that the correct profile will be ground in the cutter X. When the template 900 is correctly made, the finger 800 has correct dimension and the dividing head is adjusted to correct position on the bracket 430, the cutter X will be ground to a correct diameter. It may, however, be quite a lot of tungsten carbide to grind away and it may then be necessary to move the dividing head rearwardly on the bracket 430 with the hand wheel 435 before grinding begins.

The table 301 is moved continuously along the path which is defined by the finger 800 and the template 900 and the grinding step for the diamond wheel is adjusted with the hand wheel 435. When two opposing tips of tungsten carbide have been ground to the same value on the scale for the hand wheel 435 the diameter of the cutter X may be checked. In this way each tip on the cutter is ground until there is 0.05 mm left to grind. The last 0.05 mm on each tip is ground without moving the hand wheel 435 and only by adjusting the button 440 and the wheel 408 to bring all the tungsten carbide tips in position for grinding one by one. The final grinding in this way provides for closer tolerances so that all tungsten carbide tips or bits will have edges on the same cutting circle.

Two of the grinding operations required for grinding of cutters having hard metal bits and designed for wood-working have now been described. It is to be noted that no adjustment of the cutter X with the hand wheel 450 is required after grinding of the top face of the tungsten carbide tips. The clearance angle of 1 50 or 600 in relation to the face of the tungsten carbide tips will come automatically.

The motion of the table 301 in the y-direction can be locked in a suitable position while the table is movable freely only in the x-direction. In this way the machine can face-grind a tool. This means that the machine can carry out all grinding operations on a tool including face-grinding and grinding of clearance angle also on tools having a complicator and accurate shape or profile.

The front face of the cup shaped grinding wheel 780 has always to be at the same level in the grinding machine, when the spindle housing 220 is in vertical position for face-grinding of the tip supporting face. When the grinding wheel 780 becomes worn, it is sufficient to interchange a ring between the grinding wheel and a shoulder on the spindle housing 220 with a ring which is thicker, so that the front face of the grinding wheel again will be in the correct position.

The dividing head is as mentioned previously located on a bracket 430 at an angle corresponding to the chosen standardized chip angle which for tungsten carbide tips on woodworking tools is 150. On the bracket 430 there is a scale giving the radius for the tool to be ground.

When the dividing head 401 is in the foremost and lowest position the centerline for the spindle in the dividing head 402 and therefore also the tool X will be at the same level as the front face of the diamond wheel 780. In this position the scale on the side of the bracket 430 will indicate zero tool diameter. When the dividing head 401 is moved 50 mm rearwardly and upwardly on the bracket 430, the scale will indicate a tool radius of 50 mm and correspondingly a tool radius of 100 mm if the dividing head 401 is moved further upwards on the bracket 430 so that the scale indicates 100 mm radius. This is shown on Figure 8. In this position the centerline for the spindle in the dividing head 401 and therefore also the centerline of the tool X will be lifted sufficiently to give a correct chip angle.

For all other tool diameters within the limits for motion on the bracket 430 corresponding conditions will be obtained. The face viz. the supporting face for the tip on the tool X to be ground will remain in the same position as far as the level is concerned, and also in regard to the motion of the table 301 in the direction x. The motion of the table 301 in the x-direction for grinding of the supporting face can be very short irrespective of the diameter of the different tools.

The adjustment of the grinding depth is made by a slight turning of the dividing head. The operating device 450 will carry out this motion of the tool X and the indicator 455 will show the motion.

Grinding of the clearance angle and the external diameter of the tool is made by an edge grinding wheel 700 and with the spindle housing 220 positioned horizontally or close to the horizontal line. The center of the bearing in the bracket 201 on which the spindle housing 220 rotates when it is brought to horizontal position is lower than the front of the grinding wheel 780 when the spindle is vertical, so that the circumference of the grinding wheel 700 defines an angle corresponding to the chip angle in relation to the supporting face on the tool X. If it is presumed that the diameter of the grinding wheel 700 is 100 mm, the angle between the face of the tool X and the circumference of the grinding wheel 700 when the spindle housing 220 is in horizontal position and the distance from the tool X to the center of the bearing for the bracket 201 is 28.9 mm.

The angle on the bracket 430, the scale on same, the distance from the front of the grinding wheel 780 to the center of the bracket 201 and the diameter of the grinding wheels form a geometrical system which automatically will give the tools correct chip angle, cutting angle and clearance angle, the angles being built into the machine. In the few cases when other cutting angles are required, the machine can be readjusted by adjustment of the grinding wheel 780 to another position on the spindle and by rotating the tool with the hand wheel 750 before grinding of the clearance angle. Further, in addition to what has been explained above, the machine in the embodiment shown on Figure 1 and 2, comprise a base frame 111 for the table 301. The table 301 can be locked in any position with the lock 330 on one side and 331 on the other side (Fig. 2).The bracket 201 for the spindle housing 220 has a mounting device 260 for an electric motor (not shown) which by means of a V-belt 272 drives the spindle for the grinding wheels 700 and 780. If required the outer grinding wheel 700 can be removed with a rapid release mechanism enclosed by a housing 233 on the outside of the V-belt 224. On Figure 2 the finger 800 is shown attached to a finger support 540 which is movable sideways by means of a hand wheel 535 on a bracket 501.

On Figures 3 and 4 the spindle is provided with a nut 235 with a groove for securing the grinding wheels 700 and 780.

On Figure 3 the spindle housing 220 is in vertical position for face grinding of the hard metal tip as shown also on Figure 8, where the cup shaped diamond wheel 780 is shown in dotted lines grinding the hard metal tip. It is evident that the angle between the hard metal tip and the wood-working tool will be the same irrespective of the diameter of the tool and 100 mm and 200 mm diameter are chosen as examples. Figures 4 and 5 show how the spindle housing 220 can be adjusted more and less than 900 on the horizontal plane for face grinding if the face of the hard metal tip is to be sloping in one direction or the other in relation to the centerline of the wood-working too!.

Figures 6 and 7 show the spindle housing and therefore also the grinding wheel 700 adjusted for grinding of side clearance above and below zero grades respectively.

The example shown will merely serve to illustrate the invention as other embodiments which are mechanically different but provides for the same adjustment possibilities for the different working components can be designed by persons skilled in the art.

Claims (7)

1. Machine for grinding of cutter tools, particularly hard metal tipped cutters for woodworking, having a movable table on which the tool is positioned for movement relative to a grinding wheel on a spindle supported in bearings in a spindle housing, characterized in that the spindle housing is adjustable for adjustment of the spindle from substantially horizontal position to a substantially vertical position.

2. Machine as claimed in claim 1, characterized in that the spindle has two spaced griding wheels.

3. Machine as claimed in claim 2, characterized in that one of the grinding wheels is a cut shaped grinding wheel.

4. Machine as claimed in claim 1, characterized in that the spindle is adjustable over an angle of more than 900 from several degrees below the horizontal plane to some degrees beyond the vertical plane.

5. Machine as claimed in claim 1, characterized in that it is provided with a dividing head for attachment of the cutting tool, the dividing head being movable on a bracket at an angle to the horizontal plane corresponding to standard chip angle.

6. Machine as claimed in claim 5, characterized in that the angle is 150.

7. Machine for grinding cutting tools substantially as hereinbefore described with reference to the accompanying drawings.