JP2564700B2 - Hard film coated drill - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard film-coated drill in which the surface of a drill body is coated with a hard film, and in particular, a hard film is formed according to the degree of demand for wear resistance of each part of the drill. The present invention relates to a drill in which the coating thickness is partially changed.

Conventional technology A hard film on the surface of the drill body, such as IV a, V in the periodic table
Hard film-coated drills have been developed in which a hard film made of a group a, VIa metal, Si or Al carbide, nitride, oxide, or a solid solution thereof is coated in a single layer or multiple layers.
The coating of such a hard film has the advantages that the welding resistance is improved and that the greater the coating thickness, the better the abrasion resistance can be obtained.

On the other hand, the rake face excluding the cutting edge flank and the margin part is coated with a hard film to improve the sharpness of the cutting edge,
When the drill body is cemented carbide, the toughness (flexural strength) decreases as the coating thickness of the hard film increases, so increase the coating thickness at the drill tip, that is, the cutting edge flank or chisel edge. It has been proposed that the margin portion on the side surface of the drill has a thin coating thickness to prevent a decrease in transverse rupture strength. The former is described in JP-A-57-184616, and the latter is described in JP-B-2-15324.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, when the coating thickness of the hard film in the margin portion is reduced or eliminated as described above, wear resistance particularly in a portion close to the drill tip portion, that is, in the vicinity of the outer peripheral corner intersecting the cutting edge However, even if the wear resistance and welding resistance are improved by increasing the coating thickness of the hard film on the tip of the drill, the drill life will be fully enjoyed. There was a problem that I could not get it.

The present invention has been made in the background of the above circumstances, the purpose is to change the coating thickness of the hard film according to the degree of demand for wear resistance of each part of the drill, well balanced drill life To improve.

Means for Solving the Problems In order to achieve such an object, the present invention is a hard film-coated drill in which a hard film is coated on the surface of a drill body,
The coating thickness of the hard film at the margin is 1.1 to 2.0 times the coating thickness of the hard film at the tip of the drill near the tip of the drill and within the range of 2 to 12 μm. It is characterized in that at a portion separated by 3 mm or more, it is less than or equal to 1/2 of the coating thickness at the portion close to the tip.

Here, the tip portion is as defined in JIS B 0171-1989 (drill term) No. 2042, and specifically, a portion constituted by a cutting edge of a drill, a rake face, a flank face and a chisel edge. Is a general term for.

Operation In other words, the progress of wear due to the use of drills was observed and measured by site, and it was found that the wear in the margin near the outer peripheral corner progressed faster and more than in the flank of the cutting edge and the chisel edge. Therefore, based on such knowledge, the coating thickness of the hard film of the portion of the margin portion close to the drill tip is 1.1 to 2.0 times the coating thickness of the hard film at the drill tip, and the drill tip and The wear resistance at the margin near the outer peripheral corners is balanced. 1.1 to 2.0 times means that at 1.1 times or less, the wear in the margin part near the outer peripheral corner becomes more remarkable than the wear of the drill tip, 2.
On the other hand, when it is 0 times or more, the wear of the tip of the drill becomes conversely more remarkable than the wear in the margin near the outer peripheral corner. Also, the coating thickness at the portion of the margin portion near the drill tip is 2 to 12 μm is 2 μm.
If it is less than m, the effect due to the difference in coating thickness cannot be sufficiently obtained,
This is because if it is 12 μm or less, peeling becomes easy.

On the other hand, in the portion of the margin portion 3 mm or more away from the drill tip, the coating thickness of the hard film is 1/2 or less of the coating thickness in the portion close to the drill tip, that is, the hard film of the drill tip. It is said that it is approximately the same as or less than the coating thickness, but this is because the portion away from the drill tip does not require so much wear resistance. Wear resistance and welding resistance are obtained, and a large decrease in transverse rupture strength is avoided when the drill body is made of cemented carbide.

Here, the coating thickness of the hard film in the margin part gradually decreases gradually as it is separated from the part close to the drill tip, and within 3 mm from the drill tip as described above, 1/2
The following conditions are desirable in order to prevent the hard film from peeling or chipping and to secure a necessary and sufficient coating thickness in the vicinity of the drill tip.

The hard film to be coated is, for example, IVa, V of the periodic table.
Carbides, nitrides, oxides or solid solutions thereof of a, VIa group metals, Si or Al are desirable, and they may be formed in a single layer or multiple layers by a usual PVD method or a CVD method.
The coating thickness of the hard film is, for example, in the PVD method, the positional relationship between the evaporation source and the drill body, that is, the direction, distance, rotation, movement, etc.
It can be changed relatively easily by appropriately selecting the vacuum degree, applied voltage, and the like. Further, in the CVD method, it can be changed by masking or the like having an appropriate gap.

When reusing a drill that has reached the end of its life due to tool cost, etc., re-grind the tip and reuse the drill body with the bare surface of the drill body exposed. However, the original hard film-coated drill can be reproduced by coating a hard film on the ground drill tip and its vicinity, that is, a portion within 3 mm from the drill tip of the margin part. Although the hard film remains in the margin portion, the coating thickness thereof is thin, and therefore a new hard film may be coated thereon.

Effects of the Invention Thus, the hard film-coated drill of the present invention, the degree of demand for wear resistance in each part of the drill, the portion close to the drill tip of the margin portion, the cutting edge flank of the drill tip or Because the hard film coating thickness is reduced in the order of the chisel edge part and the part that is 3 mm or more away from the drill tip part in the margin part, the hard film in each part of the drill works effectively and wear resistance and welding resistance The drill life can be improved in a balanced manner.

In addition, since the coating thickness of the margin portion 3 mm or more away from the drill tip is relatively thin, even when cemented carbide is used as the drill body, a significant decrease in toughness due to coating of the hard film is avoided, and it is practical. There is an advantage that sufficient transverse rupture strength is secured.

Example 1 8.5 m outer diameter as shown in FIGS. 1 and 2
A twisted drill 10 of high hardness and high speed steel AISI M43 HRC68 of m, 37 mm in blade length is coated with TiN film by PVD method, and the coating thickness of each part of the drill is as shown in Table 1 and A comparative product was manufactured, and a cutting test was performed under the following cutting conditions to investigate the number of cuts until the end of life and the cause of the life. In FIG. 1, the tip portion 12 is a general term for a portion constituted by a cutting edge, a rake face, a flank face and a chisel edge.

Cutting conditions Work material: S45C HRB90 Machining hole depth: 25mm Through hole Drill rotation speed: 974rpm Feed: 0.25mm / rev Cutting oil: Water-soluble emulsion Machine: Vertical machining center The wear resistance of each part of the drill is well-balanced and it is about 2
Double tool life was obtained.

Example 2 Outer diameter 1.0 m as shown in FIGS. 3 and 4
As shown in Table 2, the TiCN film is coated by CVD on a straight type micro drill for printed circuit board drilling of cemented carbide JIS K10 HRA92.5 with m and a blade length of 10 mm, as shown in Table 2. Inventive products and comparative products
A cutting test was performed under the following cutting conditions to investigate the number of cuts until the end of life and the cause of the life. Note that FIG. 4 is an enlarged view from the tip side.

Cutting condition Work material: Epoxy resin with glass cloth as the base material, 1.6mm thick, 3 layers stacked Drill rotation speed: 70000rpm Feed: 0.05mm / rev Cutting agent: None Machine: NC copy drill router As is clear from Table 2, this book The invented product has a well-balanced increase in wear resistance of each part of the drill. The breaking strength was also high, and the tool life was about 120-160% compared to the comparative product.

It should be noted that the above-described embodiments are merely specific examples of the present invention, and the present invention includes various modifications based on the knowledge of those skilled in the art.
It can be implemented in an improved manner.

[Brief description of drawings]

FIG. 1 is a front view of a twist drill used in the first embodiment of the present invention. FIG. 2 is a view from the tip side of the drill shown in FIG. FIG. 3 is a front view of the microdrill used in the second embodiment of the present invention. FIG. 4 is an enlarged view of the drill of FIG. 3 seen from the tip side. 10: Drill 12: Tip

Claims (1)

(57) [Claims] 1. A hard film-coated drill having a hard film coated on the surface of a drill body, wherein the hard film has a coating thickness at a margin portion at a portion close to the tip portion of the drill. 1.1 to 2.0 times the length and within the range of 2 to 12 μm,
A hard film-coated drill characterized in that a portion 3 mm or more away from the tip portion has a coating thickness of 1/2 or less of a portion near the tip portion.