Drill grinder
BACKGROUND OF THE INVENTION 
     This invention relates to an improved drill grinder. 
     The clearance angle (as defined in FIG. 9-1) and the point angle P (as defined in FIG. 9-2) of a drill bit usually have various specifications in order to meet the requirements of different purposes. However, the desired clearance and point angles of a drill bit have to be obtained by manually controlling the conventional drill grinder therefore it is difficult to achieve the accurate clearance angle or point angl e therefrom. 
     It is, therefore, an object of the present invention to obviate and mitigate the above-noted drawback. 
     SUMMARY OF THE INVENTION 
     It is the primary object of the present invention to provide an improved drill grinder which can be correctly and quickly operated and is applicable to any sizes of drill bits. 
     It is another object of the present invention to provide an improved drill grinder which is so simple to operate that even an unskilled person can produce perfect product within a short period. 
     It is still another object of the present invention to provide an improved drill grinder which is economic to fabricate. 
     It is a further object of the present invention to provide an improved drill grinder which is practical for use. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a preferred embodiment of the present invention; 
     FIG. 2 is a local perspective view of a preferred embodiment of the present invention; 
     FIG. 3 is a fragmental perspective view of FIG. 2; 
     FIG. 4 is a perspective view of a positioning seat of a preferred embodiment of the present invention; 
     FIG. 5-1 shows that the positioning seat cooperates with the clamping means to adjust the position of the drill bit clamped therein; 
     FIG. 5-2 is a side view of the clamping means wherein the drill bit is clamped between the first and the second seats; 
     FIG. 6 is a simplified top view illustrating the drill bit being contacted with the grinding wheel and defining the vertical distance B thereof; 
     FIG. 7 shows that the clearance angle can be accurately defined by the values of A and B; 
     FIG. 8 shows the grinding position of the drill bit when in operation; 
     FIG. 9-1 shows the clearance angle of a drill bit; and 
     FIG. 9-2 shows the point angle of a drill bit. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings and particularly to FIGS. 1 to 3, an improved drill grinder (10) comprises a main frame (1) which is provided with a grinding means (11) on which a grinding wheel (111) is rotatably disposed. The main frame (1) is furnished with a first seat (12) on which a rib (121) is formed. A second seat (13) provided with a rib (131) is slidably mounted on the first seat (12) to move along the rib (121) of the first seat (12). A third seat (14) is slidably mounted on the second seat (13) to move along the rib (131) of the second seat (13). A L-shaped stand (2) is formed with a hole (21). A pin (211) passes through the hole (21) of the stand (2) and is secured to the third seat (14) to let the stand (2) pivotally mounted on the third seat (14) thereby capable of changing the relative position between the stand (2) and the grinding wheel (111). A shaft (22) passes through the hole (23) of the stand (2) and is provided at one end with a handle (24). A block (3) is secured to the other end of the shaft (22). The block (3) is provided with a dovetail groove (31). The center of the block (3) is formed with a recess (32) in which a gear (33) can be disposed. A knob (34) passes through the block (3) to be secured to the gear (33) therefore when the knob (34) is rotated, the gear (33) can be rotated therewith. 
     A sliding seat (4) is furnished with a dovetail (41) which corresponds to the dovetail groove (31) of the block (3) and can be moved therealong. A rack (42) is secured to the dovetail (41) to mesh in the gear (33) so that when the gear (33) is rotated in a predetermined manner the sliding seat (4) can be moved up or down along the dovetail groove (31) of the block (3). The sliding seat (4) is provided with a supporting plate (43) of which the central line (431) intersects the central line (44) of the sliding seat (4) at an angle of 45° (FIG. 6). A pair of pins (45) are respectively formed on both sides of the supporting plate (43). 
     Referring to FIGS. 5-1 and 5-2, a clamping means (5) comprises a first seat (51) and a second seat (52). The first seat (51) can be adjusted by means of screw (53) to approach the second seat (52) so that the drill bit (54) can be properly clamped between the first and second seats (51) and (52). The second seat (52) is provided with a pair of positioning holes (55) (FIG. 5-1) which respectively correspond to the pins (45) of the supporting plate (43). The clamping means (5) can be mounted on the supporting plate (43) with the pins (45) thereof respectively inserting into the corresponding positioning holes (55). There are another pair of positioning holes (56) (FIG. 1) formed on the first seat (51) and the function thereof is similar to the positioning holes (55) of the second seat (52). 
     Referring to FIG. 4, a L-shaped positioning seat (6) is furnished with a slot (61) along which a positioning member (62) can move. The positioning member (62) is provided with a screw (63) by which it can be fixed at a specified position. There is a mark (64) formed on the top face of the positioning seat (6) to illustrate the specified position at which the positioning member (62) is located. 
     Referring to FIG. 6, after the clamping means (5) is mounted on the supporting plate (43) of the sliding seat (4) and the drill bit (54) disposed in the clamping means (5) is arranged to contact the grinding wheel (111) thereof, the vertical distance from the central axis of the handle (24) to the central axis of the drill bit (54) is defined as B. 
     In operation, firstly the drill bit (54) is disposed between the first and second seats (51) and (52). Secondly, the positioning member (62) of the positioning seat (6) is fixed at a specified position which is used to set the desired value of B. This will be described later. Thirdly, referring to FIGS. 5-1 and 5-2, the drill bit (54) is adjusted to contact the positioning member (62) and then is tightly clamped between the first and second seats (51) and (52). After so doing, the desired value of B can be accurately obtained. For example, if the positioning member (62) is fixed at the mark of 40 mm, after completing the above-noted procedure, the corresponding value of B will be set at 40 mm too. Fourthly, the clamping means (5) with the drill bit (54) fixed in the desired position is mounted on the supporting plate (43) of the sliding seat (4) as described hereinbefore. 
     The vertical distance from the central axis of the handle (24) to the central axis of the drill bit (54) is defined as A (not shown). Since the clearance angle (θ) can be accurately defined by the values of A and B we can rotate the knob (34) of the block (3) to adjust the vertical distance A thereof to a predetermined value so as to achieve the desired clearance angle (θ). For illustration, referring to FIG. 7, the angle θ1 can be accurately defined by values B (40 mm) and A (3 mm) while the angle θ2 by values B (40 mm) and A (9 mm). 
     After completing the above-noted procedures, referring to FIG. 8, the second and third seats (13) and (14) are properly adjusted to let the portion (C) of the drill bit (54) contact the grinding wheel (111), as shown in the imaginary line of FIG. 8. Then rotate the handle (24) until the portion (D) of the drill bit (54) contacts the grinding wheel (111) as shown in the solid line of FIG. 8. Thus, the clearance angle (θ) of the drill bit (54) can be accurately achieved after repeating the above-noted process a few times. Then, rearrange the clamping means (5) to make the pins (45) respectively be inserted into the positioning holes (56) of the first seat (51) and the another clearance angle can be similarly achieved. 
     Also, the point angle (P) of the drill bit (54) can be achieved by mans of adjusting the relative position between the stand (2) and the grinding wheel (111).