JPH0333363Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a clamp screw used when attaching a throw-away tip to a tool body of a cutting tool.

[Prior Art] As a technique for attaching the throw-away tip 10 to the tool body 11 of a cutting tool, the so-called screw-on method is widely known in which this is done using a clamp screw 12, as shown in FIGS. 3 to 5. ing. This screw-on method has excellent advantages, such as being able to attach the throw-away tip 10 with just one clamp screw 12, which is low cost, and also the simplest and most reliable of the many attachment techniques, as well as requiring less clamping space. .

[Problems that the invention attempts to solve] However, with this screw-on method,
As shown in FIG. 5, the truncated conical outer peripheral surface 12a ₁ of the head 12a of the steel clamp screw 12 is attached to the flat inner peripheral surface 10a ₁ of the threaded hole 10a of the throwaway tip 10. It is strongly pressed by tightening. Therefore, if the workpiece is cut in this state, the truncated conical outer circumferential surface 12a ₁ of the head 12a of the clamp screw 12 will break into the throw-away tip 10 due to the cutting heat generated at this time and the impact force received during cutting. There was a problem in that a so-called seizure phenomenon occurred on the inner circumferential surface _10a1 of the flattened portion of the screw hole 10a, and the clamp screw 12 could not be loosened even if an attempt was made to loosen it. This is because the screw hole 10a of the throw-away tip 10 is not threaded, so the clamp screw 12 is not inserted into the tool body.
1, and because the throw-away tip 10 is pressed and fixed to the tool body 11 by its pressing force, the clamp screw 12 vibrates integrally with the tool body 11 due to the impact received during cutting. However, since the throw-away tip 10 is not fixed to the tool body 11, the throw-away tip 10 behaves differently from the tool body 11 due to the impact during cutting, and the clamp screw 12
It is thought that friction occurs between the truncated conical outer circumferential surface _12a1 and the inner circumferential surface of the screw hole 10a, and the frictional heat and cutting heat generated at this time causes diffusion bonding and a seizure phenomenon. This tendency is particularly noticeable when impact force is applied, such as during interrupted cutting.

The present invention addresses the problem of fixation due to seizing between the inner circumferential surface of the threaded hole of the throw-away tip and the outer circumferential surface of the head of the clamp screw in the screw-on method in which the throw-away tip is attached to the tool body.

[Means for solving the problem] The present invention consists of a threaded part and a head having a truncated conical outer peripheral surface whose diameter gradually increases from the threaded part. The truncated conical outer circumferential surface of the clamp screw, which is attached to the tool body and comes into contact with the screw hole of the throw-away tip, is made of TiC or TiN, which is a material with lower diffusion bonding properties than the material of its head. or TiCN
It is coated with a coating layer consisting of any one of the following.

[Function] The contact surface of the head of the clamp screw that comes into contact with the threaded hole of the throw-away chip is covered with a coating layer made of a material that has lower diffusion bonding properties than the material of the head, so that the diffusion phenomenon is caused by the above coating. This layer prevents the clamping screw from seizing on the throw-away chip.

[Example] Figures 1 and 2 show an example of this invention, and the same components as those shown in Figures 3 to 5 are given the same reference numerals and explanations are omitted. do.

The clamp screw 12 includes a threaded portion 12a and a truncated conical head 12b whose diameter gradually increases from the threaded portion 12a.
It is made up of. The taper angle α of the conical surface of the head 12b is arbitrary, but is preferably in the range of about 40° to 90°. The clamp screw 12
The truncated cone-shaped contact surface (outer peripheral surface) _12a1 of the head 12a is made of a material having lower diffusion bonding properties than the material of the head 12a (for example, steel), and is formed by depositing a material with a thickness of 2 μm to 5 μm by various means such as physical vapor deposition. It is covered with a covering layer 14 formed to a certain thickness. Materials with low diffusion bonding properties include hard metals such as TiC (titanium carbide: Bitkers hardness 2000-2200) and TiN.
(Titanium nitride: Bitkers hardness 2800-3000) or TiCN (titanium carbonitride) is selected. These materials have low diffusion bonding properties and excellent seizure resistance. In addition, these titanium compounds have higher hardness than cemented carbide, which is the most commonly used material for throwaway tips, and are harder than other steel materials such as high-speed steel used for throwaway tips. The same is true. Therefore, when the coating layer 14 is formed of any of these TiC, TiN, or TiCN, there is a risk that the coating layer 14 will be plastically deformed by the clamping force of the throw-away chip. It will be much less than if it were. For this reason, the coating layer 14
It is also possible to maintain a constant clamping force by preventing a decrease in the clamping force due to plastic deformation.

In the above embodiment, the head 12a of the clamp screw 12 has a truncated conical tapered surface, but it may also have a convex curved surface that bulges outward.

[Effects of the invention] This invention makes the contact surface of the head of the clamp screw with a frustoconical outer peripheral surface made of TiC, TiN, or TiCN, which is a material with lower diffusion bondability than the head. The coating layer prevents diffusion bonding between the head contact surface of the clamp screw and the inner circumferential surface of the threaded hole of the throw-away tip, preventing them from burning together, and making it easy to attach and detach the clamp screw. be able to. Moreover, since the material of the coating layer is TiC, TiN, or TiCN, the coating layer is better than the most commonly used throw-away chips made of cemented carbide or other steel materials such as high-speed steel. This increases the hardness of the clamping screw, which eliminates the possibility of plastic deformation of the coating layer due to the clamping force of the throwaway tip, prevents a reduction in the tightening clearance between the throwaway tip and the clamp screw, and ensures a constant clamping force can be obtained.

[Brief explanation of drawings]

Figures 1 and 2 show one embodiment of this invention, with Figure 1 being a front view of the clamp screw, Figure 2 being a side view thereof, and Figures 3 to 5 showing a conventional cutting tool. Fig. 3 is a front view of the tool body with the throw-away tip attached, Fig. 4 is a side view thereof, and Fig. 5 is a view taken along the - line in Fig. 3. DESCRIPTION OF SYMBOLS 10... Throwaway chip, 12... Clamp screw, _12a1 ... Contact surface, 12b... Head, 14... Covering layer.

Claims (1)

[Scope of utility model registration request] A clamp screw consisting of a threaded part and a head having a truncated conical outer circumferential surface whose diameter gradually increases from the threaded part, and which attaches the throw-away tip to the tool body by passing through the threaded hole of said throw-away tip. The truncated conical outer peripheral surface of the clamp screw that contacts the screw hole of the chip is covered with a coating layer made of TiC, TiN, or TiCN, which is a material with lower diffusion bonding properties than the material of its head. A clamp screw characterized by: