JPS63207566A - Straight grinding tool with shaft - Google Patents

Abstract

PURPOSE:To make deep-infeed creep feed grinding for ceramics, etc., into high efficiency and high accuracy, by attaching the grindstone formed by diamond abrasive grains and/or CBN abrasive grains with a grit bond to one end of a cemented carbide shaft. CONSTITUTION:The grindstone 2 consisting of a cemented carbide round bar of 8mmphi and made up of mixing CBN abrasive grains and/or diamond abrasive grains and cast iron powder and molded and sintered into a cylindrical form of 10mm or so both in height and outer diameter is fitted in one end of a shaft 1 of about 62000kg/mm<2> in elastic modulus, while it is tightly attached to the shaft by means of brazing (3), setting it down to a mounted straight grinding tool. And, when deep infeed creep feed grinding takes place on a workpiece 5 of the ceramics, etc., clamped onto a table 4, grinding force is abated because holding force of abrasive grains of th grindstone 2 is large and, what is more, rigidity in the shaft 1 is high enough, and simultaneously waviness on a grinding surface becomes lessened. Thus, highly efficient and accurate creep feed grinding is made performable.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a shaft-mounted straight grinding tool using a diamond and/or CBN grinding wheel, and in particular, the grinding tool is formed by bonding abrasive grains with cast iron and has a high rigidity. This invention relates to a straight grinding tool with a shaft that enables deep-cut creep feed machining of difficult-to-cut materials such as ceramics, cemented carbide, and hardened steel with high precision and high efficiency.

[Prior Art] Grinding involves rotating a grinding wheel at high speed, and using the cutting edges of many abrasive grains protruding from the working surface of the grinding wheel, microscopic chips are removed from the workpiece to achieve the desired shape, size, and size. This is a processing method that produces products with a high-quality surface finish, and a diamond whetstone is made by hardening diamond abrasive grains with a suitable bonding agent (hereinafter referred to as "bond").

On the other hand, CBN is cubic boron nitride.
onNitride), which has the same crystal structure as diamond and is second in hardness to diamond.
It is a tool material that can be compared to diamond. In particular, C.B.
Since N is more stable than diamond against heat and more inert than diamond against iron, it is suitable for machining hardened special steel.

These diamond and CBN abrasive grains are hardened by four types of bonding or bonding methods as described below.
Used as a grinding wheel.

1) Resinoid bond grindstone Abrasive grains and thermosetting resin powder are mixed, placed in a mold, and hot-pressed to form.

2) Metal bonded grindstone This grindstone uses sintering metal powder to bond abrasive grains by powder metallurgy. In many cases, a bond mainly made of bronze is used.

3) Vitrified bond grindstone A mixture of several types of hard mineral powder and abrasive grains is pressed and formed, and fired in a furnace.

4) Plated bonded whetstone This is a whetstone in which the base metal is used as a cathode, abrasive grains are placed on top of it, and the abrasive grains are bonded to platinum by electroplating.

In any of the above bonds, the abrasive grain holding power of the bond is not sufficient, or the cutting edge of the abrasive grains is expected to self-generate due to abrasion and falling off on the working surface of the grinding wheel, which makes the bond brittle to some extent, so the depth of cut is It is impossible to grind with a large thickness. Therefore, when using a shaft-equipped straight grinding tool to erase difficult-to-grind materials such as ceramics, cemented carbide, hardened steel, and composite materials, it is necessary to reduce the depth of cut and grind repeatedly. In terms of grinding performance, grinding efficiency, and impact on the workpiece, there has been a desire for a straight tool with a shaft that can perform deep creep feed.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems of shafted straight grinding tools using diamond and/or CBN grinding wheels. A straight grinding tool with a shaft that enables deep-cut creep feed machining of difficult-to-grind materials such as composite materials, as well as reducing uncut residue during machining and reducing grinding resistance to achieve high efficiency and high grinding. The purpose is to provide

[Means for Solving the Problem 1] As a result of extensive research into grinding wheels using diamond abrasive grains and/or CBN abrasive grains, the present inventors found that among metal bonded grinding wheels, cast iron bonded ones were superior to conventional resinoid grinding wheels. In fact, we focused on the fact that the abrasive retention is extremely higher than that of bronze metal bond and plating bond, and that deep-cut creep feed cutting is possible. The present invention was completed based on a new idea of using cemented carbide as the shaft material.

The gist of the straight grinding tool with a shaft of the present invention is that it consists of a grindstone made of diamond abrasive grains and/or CBN abrasive grains formed by bonding cast iron, and a shaft made of cemented carbide to which the grindstone is attached to one end. do.

[Function] The diamond and/or CBN abrasive wheel of the present invention is formed by bonding diamond abrasive grains and/or CBN abrasive grains with a cast iron bond, so it has high abrasive grain retention and is capable of deep cutting creep feed machining. . In normal grinding performed using a conventional grindstone, the cutting depth of the grindstone is on the order of 1/100 mm, and the workpiece feed rate is on the order of 10 m/min. On the other hand, in deep-cut creep feed grinding, the grinding wheel depth of cut reaches the 1.0 ■ level, and conversely, the feed rate is 10 m.
It is as low as m/min. As a result, in creep-feed grinding, the contact arc length between the grinding wheel and the workpiece is 10~
It will be 100 times more.

Of course, high-rigidity machines are required to perform creep-feed grinding with high efficiency and high precision, but tool rigidity plays a very large role. In the present invention, since the shaft of the straight tool with a shaft is made of cemented carbide, the rigidity of the tool can be significantly increased. An example of the components of cemented carbide and its elastic modulus is WC:
92%, TiC; 2%, CO; 6%, elastic modulus; 62.0
00kg/mm". In other words, while the modulus of elasticity of a conventional steel shaft is 20, OO0kg/mm2,
The elastic modulus of the cemented carbide shaft is 62, OO0kg7mm2
Therefore, it is expected that the rigidity will be improved by about three times compared to the conventional one. As described above, in the present invention, since the rigidity of the tool itself is increased, the grinding resistance is significantly reduced, and the waviness of the grinding surface, that is, the amount of uncut material is reduced.

[Example] In order to clarify the effects of the present invention, an example will be described while comparing with a conventional example.

FIG. 1 is a side sectional view of an embodiment of the present invention, and FIG. 2 is a plan view of FIG. 1. In the figure, the shaft 1 is a round bar with a diameter of 8 mm, and is made of cemented carbide, and its composition is WC; 92%; TiC;
2%, Co: 6%, elastic modulus: 62, OOOkg
/mm2. Grinding wheel 2 is made of CBN abrasive grains (abrasive grain size #120)
~140) and cast iron powder, formed into a cylindrical shape, and sintered.The CBH concentration is 200 (CBN content is 50% of the volume ratio), and the outer diameter and height are both 10 mm. This grindstone 2 was fitted by cutting one end of the shaft 1, and was also fixed to the shaft 1 by brazing 3 to form a straight grinding tool with a shaft.

For comparison, a straight grinding tool with a shaft of the same dimensions was prepared, with the shaft 1 made of steel and using the same CBN grindstone 2. Next, a grinding test was conducted using the tools of the present invention example and the comparative example, and the grinding resistance and waviness of the ground surface were measured. The machine tool used was a modified Brother High Millet machine, and as shown in the perspective view of Figure 3, the grindstone 2 mounted vertically was applied to the workpiece 5 fixed on the table 4, and the table 4 was fed. By doing this, we performed a cleaning process. The material of the work material 5 is 5KH-9 (high speed m) quenched product, hardness HRa.
63-65. The cutting conditions were: depth of cut 1mm;
The cutting width was 5II1 m, the tool rotation speed was 2400 rpm (grinding wheel peripheral speed 75 m/min), and the table feed speed was 2.55 mm/min.

The grinding resistance was measured using a Kisla stress measuring device, and the measurement results are shown in FIG. 4 (a) for a comparative example and in FIG. 4 (b) for an inventive example. As is clear from FIG. 4, the stress in the Fz force direction is 5.8 to 10.8 kg in the comparative example, while it is 1.1 to 3.3 kg in the example of the present invention, and the stress in the grinding of the example of the present invention is It was confirmed that the resistance was extremely low.

The waviness of the cut surface was measured using a surface roughness meter manufactured by Tokyo Seimitsu Co., Ltd., and the measurement results are shown in FIGS. 5(a) and 5(b). The measurement results of the comparative example are shown in Figure 5 (a), and the measurement results are approximately 1.5 m.
In contrast to the large undulations with a depth close to 1 μm over the range of 1 μm, almost no undulations were observed in the example of the present invention, as is clear from Figure 5 (B). It was confirmed that high-precision grinding is possible.

Although this example shows a grinding test of hardened high-speed steel using a CBN grindstone, it was confirmed that similar results can be obtained when ceramics are ground using a diamond grindstone. In addition, diamond abrasive grains and CB
Good results have also been obtained when a difficult-to-cut composite material is ground using a grindstone mixed with N abrasive grains.

[Effect of the Invention 1] As explained above, the shaft-equipped straight grinding tool of the present invention has a grindstone formed by bonding diamond abrasive grains and/or CBN abrasive grains with a cast iron bond, so that the holding force of the abrasive grains is improved. It is large and enables deep-cut creep-feed grinding of difficult-to-grind materials such as ceramics, cemented carbide, and hardened steel, which was impossible with conventional grinding wheels. In addition, since the shaft is made of highly rigid cemented carbide, the grinding resistance is reduced and the waviness of the grinding surface is reduced, making highly efficient and highly accurate creep feed grinding possible. Furthermore, as the rigidity of the shaft is improved, it is possible to reduce the diameter of a straight tool with a shaft, which is particularly effective for thin grooving.

[Brief explanation of the drawing]

Fig. 1 is a side view of an embodiment of the present invention, Fig. 2 is a plan view of Fig. 1, Fig. 3 is a perspective view of a grinding test, and Fig. 4 (A) and (B) are measurement results of grinding resistance. Figure 5 (A) (B)
FIG. 3 is a diagram showing measurement results of waviness on the ground surface. 1...Shaft, 2...Whetstone, 3...Brazing Fig. 1 Sacrifice 3

Claims (1)

[Claims] (1) A straight grinding tool with a shaft, characterized by comprising a grindstone made of diamond abrasive grains and/or CBN abrasive grains formed by bonding cast iron, and a shaft made of cemented carbide to which the grindstone is attached to one end.