JP5455089B2 - Head detachable cutting tool - Google Patents

Description

  The present invention relates to a head detachable cutting tool for detachably fastening a cutting head having a cutting edge to a shank portion using a devised joint.

  Examples of the prior art of the above-mentioned cutting tools include those disclosed in Patent Documents 1 to 4 below.

  The cutting tool (ball end mill) of Patent Document 1 includes an end mill head, a shank, and a pull rod that is screwed into the end mill head. The end mill head and the shank include a butting surface that is substantially perpendicular to the tool center axis. And the shank are pulled together by the pull rod, and the butted surfaces are butted together and fastened.

  Moreover, the cutting tool (milling tool) of patent document 2 is comprised by the cutting head, the shank, and the holding means, the holding means inserted in the taper hole of the shank tip is screwed in a shank, and an effect | action of a fitting part with a taper hole The holding means is engaged with the cutting head, the cutting head is pulled into the tapered hole, and the cutting head is fastened to the shank by being taper-fitted to the shank.

  The blade part exchangeable cutting tool of Patent Document 3 has a structure substantially similar to that of the milling tool of Patent Document 2. The fixing member engaged with the blade part is inserted into the insertion hole provided at the tip of the tool body and screwed into the tool body to draw the blade part toward the tool body, and the butting surface of the blade part is the tip of the tool body. And the blade portion is fastened to the tool body.

  Further, in the cutting tool of Patent Document 4, a male screw for fastening is formed on a male member corresponding to a cutting head, and the male member is screwed into a female screw (screw hole) of a female member corresponding to a shank. Fasten to female member. The male thread is a screw that does not include an incomplete thread in order to shorten the length of the tool joint and maintain strength, and the shoulder surface (axial end surface) of the male member faces the tip of the female member at the fastening completion position. At the same time, the root portion of the male screw of the male member is taper-fitted to the inlet of the screw hole of the female member.

Special table 2001-500801 gazette Special table 2001-505137 JP 2008-6508 A Japanese Patent No. 4117131

  Since the cutting tool of Patent Document 1 operates the pull rod from the rear end side of the shank to transmit the pulling force to the end mill head, the detachability operability is not good. In addition, the end mill head can be replaced while the shank is mounted on the processing machine, so that it cannot be replaced on the machine, and the usability is poor.

  Further, the end mill head is constrained by a combination of screw fitting or cylindrical fitting of the pull rod to the shank, taper fitting of the end mill head, butting of the end face in the axial direction (butting surface) of the end mill head and the shank. This is a so-called three-surface constrained structure. For this reason, when high-precision management of blade runout is performed, high machining accuracy is required, and reduction in productivity and increase in cost are inevitable.

  Further, since it is extremely difficult to process the screw fitting portion where the male screw and the female screw are in close contact with each other, in the restraint at the screw fitting portion, an inadequate contact portion due to an inevitable processing error (gap g in FIGS. 14 and 15). ) Occurs, and accuracy and fastening reliability are likely to be insufficient. FIG. 14 shows fastening using only a screw in the conventional method, and FIG. 15 shows fastening using both a tapered surface and a screw.

  The cutting tools of Patent Documents 2 and 3 have the same problems as the tool of Patent Document 1. In addition, since the locking projection provided on the holding means (blade portion fixing member) is engaged with the cutting head (blade portion) by using the action of the tapered surface, the contact area of the locking portion is inevitable. The reliability of fastening and holding in high load cutting is low.

  Moreover, the cutting tool of patent document 4 has a small effective fitting area of the tool joint which consists of a male screw and a female screw, and lacks the reliability of the loosening prevention of a connection part. In addition, since the mating area of the taper mating surfaces of the male and female members is extremely small, the ability to withstand loads in the direction perpendicular to the axis is particularly small, and the male member moves during high-load cutting to ensure high machining accuracy. Is difficult.

  An object of the present invention is to enable a detachable cutting tool to be firmly and reliably fastened with a structure that is excellent in detachability operability and usability and does not require high machining accuracy.

In order to solve the above problems, the present invention comprises a cutting head, a shank, and a helical coil-shaped fastening aid having elasticity,
The cutting head has a taper shaft portion, a torsion groove formed on the outer periphery of the taper shaft portion, and a flat shoulder surface projecting radially outward from the base of the taper shaft portion at the rear portion,
A front end surface with which the shank abuts the shoulder surface, a tapered hole opened in the front end surface that receives the tapered shaft portion in conformity, and an inner surface of the tapered hole corresponding to a torsion groove on the outer periphery of the tapered shaft portion Having a twisted groove formed in
The fastening aid has a cross-sectional shape substantially similar to a space formed between a torsion groove on the outer periphery of the tapered shaft portion and a torsion groove on the inner surface of the taper hole,
The fastening aid is attached to one of a twist groove on the outer periphery of the taper shaft portion and a twist groove on the inner surface of the taper hole, and in this state, the taper shaft portion is inserted into the taper hole. Enters both the torsion groove on the outer periphery of the tapered shaft portion and the torsion groove on the inner surface of the taper hole, and is elastically pressed against the groove surfaces of both the torsion grooves,
Provided is a detachable cutting tool in which the shoulder surface is in close contact with the front end surface of the shank, and the outer peripheral surface of the tapered shaft portion is in close contact with the inner surface of the tapered hole so that the cutting head is fastened to the shank.

  The installation pitch of the torsion groove on the outer periphery of the taper shaft portion and the torsion groove on the inner surface of the taper hole is larger than the groove width of the torsion groove in order to taper-fit the taper shaft portion and the taper hole. The outer peripheral surface of the taper shaft portion and the inner surface of the taper hole remain.

The cutting tools are preferably those listed below.
(1) The fastening aid has a tapered helical coil shape, and the winding pitch of the coil in a free state is smaller than the installation pitch of the torsion groove, and this fastening aid is stretched to extend the outer periphery of the tapered shaft portion. Mounted on either the twisted groove or the twisted groove on the inner surface of the tapered hole.
(2) When the fastening aid is stretched to a position where the winding pitch of the spiral coil becomes equal to the installation pitch of the torsion groove, the fastening aid becomes the taper angle of the tapered shaft portion or the tapered hole. and also of it was to have approximately equal taper angle.
(3) The fastening aid has a substantially parallelogram-shaped cross section, and one set of diagonal corners of the cross section is disposed on the inner diameter side and the outer diameter side of the spiral coil.
(4) The fastening aid is made of a material softer than the material of the cutting edge, more preferably steel.
(5) The contact area between the outer peripheral surface of the taper shaft portion and the inner surface of the taper hole is ensured by 75% or more in comparison with the mutual contact area without the twisted groove.
(6) The torsion angle of the torsion groove on the outer periphery of the tapered shaft portion and the torsion groove on the inner surface of the taper hole is set in a range of 75 ° or more and less than 90 °.

  The cutting tool according to the present invention has a function in which a helical coil-shaped fastening auxiliary tool mounted on one of a torsion groove on the outer periphery of the taper shaft part and a torsion groove on the inner surface of the taper hole functions as a screw thread. Is screwed into the tapered hole of the shank. Then, the shoulder surface provided on the cutting head is brought into close contact with the front end surface of the shank, and at the same time, the outer peripheral surface of the taper shaft provided on the cutting head is brought into close contact with the inner surface of the tapered hole provided in the shank.

  According to this structure, only the fitting surface of the taper shaft portion and the taper hole (the outer peripheral surface of the taper shaft portion and the inner surface of the taper hole) is required for high-precision machining, and high-precision management of blade runout is required. This eliminates the problem of lowering productivity and increasing costs.

  Further, the positioning (centering) of the cutting head in the radial direction is performed by the tapered shaft portion that can secure a wide fitting area and the fitting portion of the tapered hole. In addition to this, axial positioning and position holding are performed by the abutting portion between the shoulder surface provided on the cutting head and the tip surface of the shank. Therefore, the position holding position of the cutting head is highly reliable and the processing accuracy is also improved. To do.

  Furthermore, since the taper shaft portion of the cutting head is screwed into the taper hole of the shank by causing the fastening aid to function as a thread, the attaching / detaching operation is not complicated and the cutting head can be replaced on the machine.

  In addition, since the fastening aid is a so-called spring and has elasticity, the winding pitch of the coil in the free state is made smaller than the installation pitch of the twisted groove and is stretched to form one twisted groove. By mounting, this fastening aid can be elastically pressed (hugged) against the groove surface of the torsion groove on the mounting side.

  When the fastening aid is screwed into the other torsion groove in this state, the fastening aid is also pressed against the groove surface of the other torsion groove, and the fastening is prevented from being loosened (rotation of the cutting head in the loosening direction) is ensured. As a result, the fastening of the cutting head to the shank is strengthened.

  The operation and effect of the configuration preferred in the above will be described later.

Side view showing an example of the cutting tool of the present invention The side view which decomposes | disassembles and shows the component of the cutting tool of FIG. The side view which expands and shows the taper shaft part provided in the cutting head of the cutting tool of FIG. Sectional drawing which expands and shows the taper hole provided in the shank of the cutting tool of FIG. Sectional drawing when the fastening aid used in the cutting tool of FIG. 1 is in a free state Sectional drawing which expands and shows the fastening part of the cutting head and shank of the cutting tool of FIG. Sectional drawing which expands and shows a part of fastening part of FIG. The figure which shows the other cross-sectional shape of a twist groove Diagram showing cutting vibration data obtained in the performance evaluation test The figure which shows the cutting vibration data of invention item 2 obtained by the performance evaluation test The figure which shows the cutting vibration data of invention products 1 and 2 obtained by the performance evaluation test The figure which shows the measurement result of the processing surface roughness with invention products 1 and 2 The figure which shows the measurement result of processing accuracy in the performance evaluation test Figure showing exaggerated general screw fitting part The figure which exaggerates and shows the fastening part which used the taper fitting part and the screw together

  Embodiments of the head detachable cutting tool according to the present invention will be described below with reference to FIGS.

  An exemplary cutting tool is an application of the present invention to a square end mill, and includes a cutting head 1 having a known outer peripheral edge, bottom edge, chip pocket, gash, etc., a shank 2 for fastening the cutting head 1, and a cutting head 1. And the fastening aid 3 that assists the fastening of the shank 2 and maintains the fastening state.

  The cutting head 1 has a taper shaft portion 4, a twisted groove 5 formed on the outer periphery of the taper shaft portion 4, and a flat shoulder surface 6 projecting radially outward from the base of the taper shaft portion 4 while the tip end side is narrowed. At the rear.

  The torsion groove 5 is a groove having a torsion angle θ shown in FIG. 3, and the installation pitch P of the groove is set to be larger than the groove width W of the torsion groove, and the outer periphery of the taper shaft portion 4 is tapered. The surface 4a is left.

  The shank 2 has a front end surface 7 against which the shoulder surface 6 of the cutting head abuts, a tapered hole 8, and a twisted groove 9 formed on the inner surface of the tapered hole 8 so as to correspond to the twisted groove 5 on the outer periphery of the tapered shaft portion 4. Have. The taper hole 8 opens in the front end surface 7, and the taper shaft portion 4 of the cutting head is inserted therein.

  The taper angle α of the taper shaft portion 4 shown in FIG. 3 and the taper angle α1 of the taper hole 8 shown in FIG. 4 are equal, and the taper shaft portion 4 is received in conformity with the taper hole 8.

  Further, the groove width W1, the twist angle θ1, and the installation pitch P1 of the twist groove 9 shown in FIG. 4 are equal to the groove width W, the twist angle θ, and the installation pitch P of the twist groove 5, respectively. The taper inner surface 8a also remains.

  The fastening aid 3 has a cross-sectional shape substantially similar to a space S (see FIG. 7) formed between the torsion groove 5 on the outer periphery of the tapered shaft portion 4 and the torsion groove 9 on the inner surface of the taper hole 8. The fastening aid 3 is formed of a spring steel wire or the like and has elasticity. Further, the appearance is a tapered helical coil shape, and the winding pitch of the coil in the free state is smaller than the installation pitch of the twisted grooves 5 and 9.

  In the illustrated cutting tool, the fastening aid 3 is stretched and attached to either the twisted groove 5 on the outer periphery of the tapered shaft portion 4 or the twisted groove 9 on the inner surface of the tapered hole 8. Here, the description will be made on the assumption that the groove 9 is mounted.

  When the end of the small diameter side of the fastening aid 3 is inserted into the twisted groove 9 on the inner surface of the taper hole 8, and then the fastening aid 3 is rotated while being inserted (when fitted to the twisted groove 5, it is rotated and fitted). The fastening assisting tool 3 is stretched by a thrust acting between the groove surface of the twisted groove 9 and is fitted into almost the entire region of the twisted groove 9.

In the mounted state (fitted state), the fastening aid 3 is pressed against the groove surface of the torsion groove mounted by elastic restoring force.

  In this state, the fastening aid 3 is caused to function as a screw thread, and the taper shaft portion 4 of the cutting head 1 is screwed into the taper hole 8 of the shank 2. At this time, a thrust is generated by the relative rotation of the tapered shaft portion 4 and the tapered hole 8 in a state where the twisted groove 5 is in contact with the fastening aid 3, and the tapered shaft portion 4 is drawn into the tapered hole 8 by the thrust. At the screwing end point, the fastening aid 3 is elastically pressed against the groove surface of the twisted groove 5.

  Then, at the screwing end point, the outer peripheral surface 4a of the taper shaft portion 4 is in close contact with the inner surface 8a of the taper hole 8, and at the same time, the shoulder surface 6 of the cutting head is in close contact with the front end surface 7 of the shank. The conclusion of is completed.

  The object of the invention can be achieved by using the semicircular grooves shown in FIG. 8A or the trapezoidal grooves shown in FIG. The groove is easy to process. The triangular groove creates a parallelogram space S between the twisted grooves 5 and 9. Therefore, the cross-sectional shape of the fastening aid 3 that is similar to the space S is a substantially parallelogram, and a wide contact area of the fastening aid 3 with the groove surfaces of the torsion grooves 5 and 9 is ensured. Therefore, it can be said that it is advantageous also in terms of prevention of loosening of fastening.

  The cutting head 1 has a cutting edge made of a hard material such as cemented carbide, cBN, single crystal diamond, or polycrystalline diamond as a preferable form when comprehensively considering processing performance, durability, and economy. The parts other than the cutting edge that are formed may be made of steel or cemented carbide.

  The shank 2 is preferably made of steel or cemented carbide because of its excellent economic efficiency and workability during production.

  The fastening aid 3 may be formed of a softer material than the cutting edge material, preferably spring steel. It is possible to increase the hugging force with respect to the torsion groove by reducing the diameter of the one to be attached to the torsion groove 9 at the time of attachment and expanding the diameter to be attached to the torsion groove 5.

  The twist angles θ and θ1 of the twist grooves 5 and 9 are suitably in the range of 75 ° or more and less than 90 °. As the twist angles θ and θ1 approach 90 °, a stronger axial tightening force can be generated, and the loosening of the fastening can be made difficult to occur. Moreover, it can also avoid that the attachment / detachment time of the cutting head 1 becomes too long by setting it as said angle range.

  Further, the mutual contact area between the taper shaft portion 4 and the taper fitting portion of the taper hole 8 (contact area between the outer peripheral surface of the taper shaft portion and the inner surface of the taper hole) is to strengthen the radial restriction of the taper shaft portion 4. In addition, the mutual contact area should be as large as possible within a range where the sizes of the twist grooves 5 and 9 and the fastening aid 3 are not sacrificed.

  As for the mutual contact area, the mutual contact area when the outer peripheral surface of the taper shaft portion 4 and the inner surface of the taper hole 8 are brought into contact with each other without the twisted grooves 5 and 9 being 100, and a ratio of 75% or more is secured. It is recommended.

  The taper angles α and α1 of the taper shaft portion 4 and the taper hole 8 are considered to be about 5 ° to 10 °. However, the present invention is not limited to this, and the force and screwing required for the screwing operation of the taper shaft portion 4 are not limited thereto. The value can be set to an arbitrary value in consideration of the balance between the amount and the radial restraint force generated in the taper fitting portion.

  In addition, the shoulder surface 6 of the cutting head and the front end surface 7 of the shank are excellent in workability when they are perpendicular to the axis, but they may be surfaces where both are tapered.

Tool diameter: φ25 mm, full length: 250 mm, length from the tip of the cutting head 1 to the shoulder surface 6: 72 mm, root diameter of the taper shaft portion 4: φ13 mm, taper shaft portion 4 length: 21 mm, taper shaft portion 4 Taper angle α: 7 °, torsion angle θ of torsion groove 5: 85.8 ° to 84.8 °, installation pitch P of torsion groove 5: 3 mm, free-end large diameter end dimension of fastening aid 3: outer diameter φ14 An end mill having the structure shown in FIG. 1 was manufactured as a trial product of .63 mm, inner diameter φ11.5 mm, number of blades 6, cutting edge material: cemented carbide, and material of the main body of the cutting head: die steel (SKD material).
The prototype end mills were of two types, one using a steel shank (Invention 1) and one using a cemented carbide shank (Invention 2).

  Next, using the above-described invention products 1 and 2 and a comparative end mill, machining is performed under the following conditions at a machining center of the specification of BT40, and the cutting vibration and machining accuracy (machining surface roughness and wall squareness) at that time are Compared. Two types of end mills for comparison were used: a four-blade high-speed steel (high-speed) end mill (Comparative product 1) with a tool diameter: φ26 mm, and a four-blade tip changeable end mill (Comparative product 2).

・ Cutting conditions Work material: S50C
Processing form: Down cut Dry cutting Cutting speed Vc: 50 m / min
1-blade feed amount fz: 0.03 mm / blade, 0.05 mm / blade Axial cut amount ap: 10 mm, 38 mm
Radial cut depth ae: 0.1 mm and 0.5 mm
Tool protrusion OH from the gauge line of the spindle arbor: Invention product 1, 2 = 130 mm, comparison product 1 = 60 mm, comparison product 2 = 35 mm

  The measurement results of the cutting vibration in the performance evaluation test are shown in FIGS. FIG. 9 shows Vc: 50 m / min, fz: 0.03 mm / blade, ap: 10 mm, ae: cutting vibration at 0.1 mm, and FIG. The conditions are the same as those in FIG. 9), and FIG. 11 is Vc: 50 m / min, fz: 0.03 mm / blade, ap: 38 mm, ae: 0.1 mm and 0 for Inventions 1 and 2 Cutting vibration at 5 mm.

  Furthermore, the measurement results of the machined surface roughness of Inventions 1 and 2 are shown in FIG. 12, and the inventions under the processing conditions of Vc: 50 m / min, fz: 0.03 mm / tooth, ap: 10 mm, ae: 0.1 mm FIG. 13 shows the measurement results of the squareness of the wall surface of the comparative product.

  As a result of this test, the inventive cutting head did not come off during cutting. In addition, although the chatter mark was slightly generated on the processed surface in the inventive product 1, as can be seen from FIG. 9, the cutting vibrations of the inventive products 1 and 2 have more blades than the comparative product, and the tool protrusion amount is also higher than that of the comparative product Despite being large, there was no significant difference from the comparison products 1 and 2, and data that could be said to be equivalent was obtained.

  In addition, as can be seen from FIG. 13, the squareness of the wall surface has a maximum error of 15 μm for the comparative product 1 and a maximum of 40 μm for the comparative product 2. Inventive products 1 and 2 both have an error of less than 10 μm (inventive product 2 has an error close to 0), and the machining accuracy is clearly superior to that of the conventional product. From this result, it can be seen that the cutting head and the shank of the inventive product are firmly and stably fastened.

  In addition, this invention can be applied also to drilling tools, such as a drill, a reamer, a milling tool, etc., and an application object is not limited to an end mill.

DESCRIPTION OF SYMBOLS 1 Cutting head 2 Shank 3 Fastening auxiliary tool 4 Tapered shaft part 4a Outer peripheral surface 5 Torsion groove 6 Shoulder surface 7 Front end surface 8 Tapered hole 8a Inner surface 9 Torsion groove θ, θ1 Torsion angle α, α1 Taper angle P, P1 Installation of twist groove Pitch W, W1 Groove width S Space g formed between twisted grooves

Claims (6)

The cutting head (1), the shank (2), and a helical coil-shaped fastening aid (3) having elasticity,
The cutting head (1) has a taper shaft portion (4), a twist groove (5) formed on the outer periphery of the taper shaft portion, and a flat surface projecting radially outward from the base of the taper shaft portion (4). A shoulder surface (6) at the rear,
A front end surface (7) against which the shank (2) abuts the shoulder surface (6), and a tapered hole (8) opened in the front end surface (7) for fittingly receiving the tapered shaft portion (4); A twist groove (9) formed on the inner surface of the taper hole (8) corresponding to the twist groove (5) on the outer periphery of the taper shaft (4);
The installation pitch (P1) of the twisted groove (5) on the outer periphery of the tapered shaft portion (4) and the twisted groove (9) on the inner surface of the tapered hole (8) is the groove width (W1) of the twisted groove (5, 9). Larger than the outer peripheral surface of the tapered shaft portion (4) and the inner surface of the tapered hole (8),
The fastening aid (3) has a cross section substantially similar to a space (S) formed between a torsion groove (5) on the outer periphery of the tapered shaft portion and a torsion groove (9) on the inner surface of the taper hole. Has a shape,
The fastening aid (3) is mounted in one of the twisted groove (5) on the outer periphery of the tapered shaft portion and the twisted groove (9) on the inner surface of the tapered hole, and in this state, the tapered shaft portion (4) Is inserted into the taper hole (8), and the fastening aid (3) enters both the twist groove (5) on the outer periphery of the taper shaft and the twist groove (9) on the inner surface of the taper hole. Elastically pressed against the groove surface of the torsion groove,
The shoulder surface (6) is in close contact with the front end surface (7) of the shank, and the outer peripheral surface (4a) of the tapered shaft portion is in close contact with the inner surface (8a) of the tapered hole. Is a detachable cutting tool fastened to the shank (2).   The fastening aid (3) has a tapered helical coil shape, and the winding pitch of the coil in a free state is smaller than the installation pitch (P, P1) of the twist groove (5, 9). 3. The detachable cutting tool according to claim 1, wherein 3) is stretched and attached to one of a torsion groove (5) on the outer periphery of the tapered shaft portion and a torsion groove (9) on the inner surface of the taper hole.   When the fastening aid (3) is stretched until the winding pitch of the helical coil of the fastening aid (3) becomes equal to the installation pitch of the twisted grooves (5, 9), the fastening aid (3) The detachable cutting tool according to claim 2, wherein the taper angle is substantially equal to a taper angle (α, α1) of the taper shaft portion (4) or the taper hole (8).   The detachable cutting tool according to any one of claims 1 to 3, wherein the fastening aid (3) is formed of a material softer than a material of the cutting edge.   The ratio of the mutual contact area between the outer peripheral surface (4a) of the tapered shaft portion (4) and the inner surface (8a) of the tapered hole (8) to the mutual contact area without the twisted groove (5, 9). The removable cutting tool according to any one of claims 1 to 4, wherein 75% or more is secured.   The twist angle (θ, θ1) of the twist groove (5) on the outer peripheral surface of the taper shaft portion and the twist groove (9) on the inner surface of the taper hole is set in a range of 75 ° or more and less than 90 °. The detachable cutting tool according to any one of 5.

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