Throw-away center drill locking structure

Abstract

The present invention relates to an improved locking structure for a disposable center drill, particularly a structure that increases locking strength and thereby simplifies the tool's structural design. The disposable center drill locking structure of the present invention comprises a tool body and a center drill. The tool body is provided with a tool holder having at least two screw holes, and circular, but not entirely circular, positioning posts are provided on either side of the screw holes. The tool holder is adapted to accommodate a flat center drill that is opposed to the tool holder. The center drill has two corresponding fixing holes, which are secured to the tool holder by two bolts. Semi-circular positioning grooves are provided on either side of the fixing hole of the center drill to mate with the positioning posts of the tool holder.

Description

Technical Field

[0001] The present invention relates to an improved locking structure of a center drill, and more particularly to a center drill with a discarding structure design, which has a stable locking structure and does not generate tool deflection vibration due to torque when subjected to lateral resistance. Background Art

[0002] Conventional center drills are designed as round rods with center drill bits at both ends. The material used is high-speed steel (HSS). However, the cutting speed of HSS is limited. To improve processing efficiency, processing quality and reduce processing time, the applicant of this case changed the tool material of the center drill to tungsten carbide, which has a processing speed 5 to 20 times that of high-speed steel. The tool body and center drill were redesigned into a new type. Please refer to Taiwan Utility Model Patent Publication No. M361393 "Center Drill Tool" previously applied for by the applicant of this case. The "Center Drill Tool" No. M361393 applied by the aforementioned applicant has many progressive and innovative structural designs and is highly recognized by the tool market and users. However, there are still areas for improvement in its use. The diameter of the blade 20 is too large, which limits the center drill during drilling. For example, Figure 8 On stepped workpieces or Figure 9 Drilling a center hole in a narrow deep groove is often impossible because the diameter of the blade 20 is too large.

[0003] In addition, the center drill 30 of the center drill tool No. M361393 is fixed by a bolt 40. Figure 10 As shown, when the center drill 30 is used to chamfer the side of the workpiece, the two cutting edges of the center drill 30 will be subjected to an alternating main lateral thrust F, which generates a main lateral thrust F and a torque M on the bolt 40. Even if the center drill 30 is restricted by the positioning rod 23, there is still a slight tolerance between the center drill 30 and the positioning rod 23. Even if the tolerance value is controlled below 0.05mm, slight shaking will still occur. During the chamfering process, the center drill 30 may even produce a vibration phenomenon in a small frequency range. The higher the rotation speed, the higher the number of vibrations, resulting in a decrease in the surface roughness value and dimensional accuracy of the workpiece. Summary of the Invention

[0004] The conventional "center drill tool" No. M361393 is locked by a bolt. When the center drill is used to chamfer the side of a workpiece, it will be subjected to alternating main lateral thrusts, which will generate lateral thrusts and torque on the bolt, causing the center drill to vibrate in a small frequency range. The higher the speed, the higher the vibration frequency, resulting in a decrease in the surface roughness and dimensional accuracy of the workpiece. In addition, the blade diameter of the center drill is too large, which limits the center drill's drilling performance, especially when drilling center holes in stepped workpieces or narrow deep grooves. The large blade diameter often makes it impossible to process.

[0005] The disposable center drill locking structure of the present invention includes a tool body and a center drill. The blade of the tool body is provided with a tool holder. The tool holder is provided with at least two screw holes. Circular positioning posts that are not completely circular are provided on both sides of the screw holes. The tool holder is capable of accommodating a flat center drill that is opposite to the tool holder. The center drill is provided with two corresponding fixing holes. The center drill is locked in the tool holder by two bolts. Semi-circular positioning grooves are provided on both sides of the fixing hole of the center drill to match the positioning posts of the tool holder.

[0006] The present invention uses two bolts to strengthen the locking strength between the center drill and the tool body. In addition to resisting the torque caused by the cutting force and avoiding the tool vibration caused by a single bolt, the increased locking strength can also simplify the flat edge structure below the two sides of the tool holder. The structure of the tool body is simplified, retaining only the flat edges above the two sides of the tool holder, so that the structure below the flat edge below the center drill is not covered by the tool holder, and the diameter can be reduced by 40%. This will not hinder the center hole processing of stepped workpieces or narrow groove workpieces, thereby improving the processing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is an exploded perspective view of the present invention;

[0008] Figure 2 It is a combination diagram of the present invention;

[0009] Figure 3 is a side cross-sectional view of the present invention;

[0010] Figure 4 This is a schematic diagram of the center drill of the present invention being locked in the tool holder to generate thrust and tightening;

[0011] Figure 5 It is a schematic diagram of the center drill chamfering construction of the present invention;

[0012] Figure 6 is a schematic diagram of the present invention for drilling a stepped workpiece;

[0013] Figure 7It is a schematic diagram of the present invention for drilling a narrow groove workpiece;

[0014] Figure 8 This is a schematic diagram of the "center drill tool" previously applied for by the applicant drilling a stepped workpiece;

[0015] Figure 9 This is a schematic diagram of the applicant's previous application for a "center drill tool" drilling a narrow groove workpiece;

[0016] Figure 10 This is a schematic diagram of the chamfering process of the "center drill tool" previously applied for by the applicant.

[0017] Explanation of symbols:

[0018] 1. Tool body

[0019] 10 knife handle

[0020] 20 blades

[0021] 21 knife holder

[0022] 211 straight edge

[0023] 221 screw hole

[0024] 23 positioning rod

[0025] 231 positioning column

[0026] 30 center drill

[0027] 31 fixing holes

[0028] 32 positioning slots

[0029] 33 straight edge

[0030] 34 drill blades

[0031] 35 cone blade

[0032] 351 cutting groove

[0033] 40 bolts

[0034] 41 bolt head

[0035] P thrust

[0036] R-Force

[0037] F Main lateral thrust

[0038] F1 lateral thrust

[0039] M, M1, M2 torque. DETAILED DESCRIPTION

[0040] The present invention discards the center drill locking structure, please refer to Figure 1 、 2 As shown, it includes a tool body 1 and a center drill 30; wherein:

[0041] The tool body 1 includes a handle 10 and a blade 20. The handle 10 can be changed to suit different blade shafts and can be configured as a straight rod or a tapered rod. The blade 20 has a blade holder 21 having first straight edges 211 on both sides thereof. The blade holder 21 has at least two screw holes 221 formed therein. Circular positioning posts 231 are provided on both sides of the screw holes 221. The blade holder 21 can accommodate a flat center drill 30 that is opposite to the blade holder.

[0042] The center drill 30 has a flat body with two fixing holes 31 in the center. Positioning grooves 32 in the form of semicircular notches are provided on either side of the fixing holes 31. The upper and lower sides of the positioning grooves 32 on either side of the center drill 30 are provided with second straight edges 33. The distal end of the center drill 30 is provided with a drill blade 34. A tapered blade 35 is provided between the drill blade 34 and the second straight edge 33. The tapered blade 35 is a cutting blade having a chip removal groove 351. The center drill 30 is secured to the tool holder 21 by two bolts 40.

[0043] See also Figure 3 As shown, the present invention provides two fixing holes 31 in the body of the center drill 30. The center positions of the two fixing holes 31 and the center positions of the two screw holes 221 of the tool holder 21 have a small offset distance e. The value of the offset distance e is about 0.15 mm. Figure 2 As shown, when the center drill 30 is inserted into the tool body 1, the positioning grooves 32 on both sides of the center drill 30 fit into the positioning columns 231 of the tool body 1 and are locked by two bolts 40. Figure 2 、 3 As shown, since the centers of the two fixing holes 31 and the centers of the two screw holes 221 of the knife holder 21 have a small offset distance e, the bolt heads 41 (such as Figure 1 As shown in FIG. 1 , the thrust P (as shown in FIG. 1 ) will push the fixing hole 31 upward and toward the blade holder 21. Figure 3 As shown), the positioning grooves 32 on both sides of the center drill 30 and the positioning columns 231 produce a force R that fits tightly together, as shown Figure 4 As shown, when the bolt 40 locks the center drill 30, a thrust P is generated to push the center drill 30 upward, and a pressing force R is generated between the positioning groove 32 of the center drill 30 and the positioning column 231 of the tool holder 21. Accordingly, the center drill 30 is locked in the tool holder 21 by the bolt 40, and the freedom in the upward, downward, left and right directions is restricted.

[0044] In addition, the arrangement of the two bolts 40 and the first straight edges 211 on both sides of the tool holder 21 can resist the torque and lateral thrust caused by the cutting force, thereby avoiding the tool vibration caused by a single bolt 40. Figure 5 As shown, the two cutting edges of the two bolts 40 bear the main lateral thrust F alternately during cutting (especially when chamfering the workpiece). The two bolts 40, the first straight edge 211 provided on the tool holder 21, and the positioning column 231 each bear an average lateral thrust F1 and the torques M1 and M2 generated by the main lateral thrust F on the bolts 40. The two bolts 40 counteract each other to prevent the center drill 30 from shaking. The positioning grooves 32 on both sides of the center drill 30 are fitted with the positioning columns 231 of the tool body 1, so that the locking force of the two bolts 40 to lock the center drill 30 is tightened. Therefore, the applicant applied for the patent in Taiwan, China. No. M361393, U.S. application No. 12 / 367,576, German application No. 202009005609.0, Japanese application No. 2010-00312 and Chinese application No. 200920137587.5 "Center drill tool" has a simplified structure of the flat edges below the two sides of the tool holder 21. The structure of the tool body 1 is simplified, and only the flat edges above the two sides of the tool holder 21 are retained, so that the structure below the flat edges below the center drill is not covered by the tool holder 21, and the diameter can be reduced by at least 40%, which makes the center drill 30 Figure 6 Stepped workpieces or Figure 7 The center hole machining of narrow groove workpieces will not be hindered; therefore, the dimensions of the tool handle 10, blade body 20 and center drill 30 can be changed according to the shape and size of the workpiece. Currently, based on the applicant's actual trial production and test results, the diameter of the blade body 20 can vary from 9.5, 12, 14.5, 19 and 24 mm, or even larger.

[0045] See also Figure 1 and Figure 2 As shown, the first straight edges 211 on both sides of the tool holder 21 are embedded with positioning columns 231, and are designed to correspond to the positioning grooves 32 provided on both sides of the center drill 30, and have precise matching tolerances. When the center drill 30 is inserted, it is positioned very accurately and quickly, and the length and tip position of the drill blade 34 do not need to be positioned or corrected. This is very convenient for the user. Saving the correction operation time means reducing the processing time, which relatively increases production efficiency.

[0046] The center drill 30 can be quickly positioned by means of the positioning posts 231 of the tool holder 21. The first straight edges 211 on either side of the tool holder 21 also have a positioning function. The distance between the first straight edges 211 corresponds to the second straight edges 33 on the upper and lower sides of the positioning grooves 32 on either side of the center drill 30, and the design also has a strict matching tolerance. The center drill 30 can be positioned when it is accommodated in the tool holder 21, and it also has the function of withstanding cutting stress.

[0047] The present invention uses two bolts to strengthen the locking strength of the center drill and the tool body. In addition to resisting the torque caused by the cutting force and avoiding the tool vibration phenomenon caused by a single bolt, the straight edge structure below both sides of the tool holder is simplified due to the increased locking strength, and only the straight edges above both sides of the tool holder are retained. The structure of the tool body is simplified, so that the structure below the straight edge below the center drill is not covered by the tool holder, and the diameter can be reduced by 40%. This will not hinder the center hole processing of stepped workpieces or narrow groove workpieces, thereby improving the cutting ability.

[0048] However, the above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Therefore, all equivalent structural changes made by using the description and illustrations of the present invention are also included in the scope of the present invention.

Claims

1. A disposable center drill locking structure comprising a tool body and a center drill; characterized in that: The tool body includes a handle and a blade, the blade body is provided with a knife seat, two sides of the knife seat are provided with first straight edges, the knife seat is provided with at least two screw holes, and circular positioning posts are provided on both sides of the screw holes, and the positioning posts are located at the ends of the corresponding inner edges of the corresponding sides of the knife seat and correspond to the middle of the screw holes. The knife seat accommodates a flat center drill that is opposite to the knife seat; the center drill has a flat body, the center of which is provided with two fixing holes, and two sides of the fixing holes are provided with positioning grooves with semi-circular notches. The end of the center drill is provided with a drill blade, and the center drill is locked to the knife seat by two bolts. When the center drill is accommodated in the tool holder, the bolt is screwed into the screw hole and the fixing hole, and the positioning column is sleeved into the positioning groove, so that the center drill is locked in the tool holder in the longitudinal and transverse directions, and the end of the center drill extends out of the tool holder.

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