JPS5816966B2 - deep hole drill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a deep hole drill, and more particularly to a deep hole drill that reduces the noise level during drilling.

It is known that there are various causes of noise, and that it depends on the vibration characteristics of the machine tool, the workpiece, and the drill, but the present invention particularly aims to reduce high-frequency noise caused by the drill body. That is.

This type of drill, called a deep hole drill or long drill, has a long overall length compared to its outer diameter, and therefore tends to generate torsional vibration and bending vibration during drilling, and this vibration generates a large amount of noise.

In particular, high-frequency noise causes discomfort to workers and is unfavorable in terms of environmental health, and there has been a strong desire to reduce it in view of recent noise regulations.

Conventionally, countermeasures have been taken solely by changing the drill specifications (core thickness, core thickness opening, groove width ratio, etc.), but none of these methods have been able to provide an appropriate noise countermeasure.

Therefore, the inventors investigated the cause and found that
I discovered the following.

As is generally known, changing the drill specifications described above can change the natural frequency.

However, there was no change in the tendency that the natural frequency was higher in the higher order region.

Incidentally, an example of the measurement results of the natural frequency of this conventional deep hole drill is shown in FIG. 5a.

Therefore, we presume that the high level of the high-order natural frequency of the drill is the main cause, and we are considering ways to reduce the level of the natural frequency, especially in the high-order region, and An attempt was made to change the natural frequency by changing the conditions and the shape of the drill.

Therefore, the present inventors first analyzed the state of stress distribution in the cross section of a conventional drill using the finite element method. As shown in FIG. It was confirmed that a stress concentration area existed within the groove 2.

The stress concentration part of the heel part 1 of the drill was removed as a means of changing the shape of the drill and changing the stress distribution state at the same time.

This is because it is easier to change the stress distribution by deleting stress-concentrated parts than by deleting parts where stress is not concentrated.

In other words, changing the core thickness of the conventional drill had no effect, so removing the stress concentration part in the main groove of the drill is the same as changing the core thickness, so the effect would be weak.
Furthermore, we thought that the originally required rigidity of the drill would be weakened, so we changed the heel shape and also changed the stress distribution state.

When we measured the natural frequencies of this drill, we found that the level of higher-order natural frequencies decreased, as shown in Figure 5, and the noise during drilling with this drill was also significantly reduced. I found out that.

The present invention was made based on the above findings, and is characterized by the fact that, in a deep-hole drill having a uniform cross-sectional shape over the entire length of the blade, a heel portion is formed approximately at the center of the heel portion along the main groove of the drill. The point is that a concave groove is provided over the length from the cut-up part of the main groove of the drill to the vicinity of the tip of the drill.

The present invention will be explained in detail below based on illustrated embodiments.

In FIG. 2, reference numeral 3 denotes a deep hole drill body, which is provided with a blade portion 5 following a handle portion 4, and a pair of main grooves 2 are provided in the blade portion 5.

6 is a concave groove provided in the heel portion 1.

Next, cutting test conditions and results of drilling tests performed on the drill according to the present invention and a conventional drill will be explained.

Drill specifications Outer diameter D: 14.7ψ Overall length: 963mm Blade length L: 763m11L Cutting conditions Work material: Fe12 Cutting speed: 335,445rpm Feed rate: 0.18m1REV (Non-tap) Hole depth = 60o Concave groove provided in the heel of the drill of the invention Length: 600 Dragon groove Depth: 2.5 Dragon groove Width: 2.5 Dragon Drilling was carried out under the above cutting conditions, and the vibration characteristics and occurrence of the drill at that time were measured. Noise was measured using a vibration meter and a sound level meter.

Figures 3a and 3b show frequency analysis results during drilling with a conventional deep hole drill, and Figure 4a.

b shows the result of frequency analysis during drilling with a deep hole drill according to the present invention, which has the same specifications as the conventional drill and has the groove in its heel portion.

Note that the noise level N is an actual value measured using a sound level meter at the same time as the vibration measurement, and is shown on the right side of the figure.

As is clear from these figures, conventional deep hole drills exhibit a vibration mode with a high frequency peak value of 20'OO to 5000 Hz during drilling, and the noise level reaches N = 97 to 1 l-OdB. When the human ear senses this, it is perceived as a high-pitched sound that is much louder than the actual noise level because the frequency is high-order.

On the other hand, in the case of the deep hole drill according to the present invention, the high frequency peak value exhibits a very small vibration mode, and the noise level is N = 93 to 97 bB, which is 4 to 1
The sound was reduced by 4 dB, and when detected by the human ear, the sound was barely perceptible compared to the conventional one.

That is, by providing a concave groove in the heel part, the natural frequency of the drill body is changed, and high-order vibration modes are suppressed, thereby reducing the overall noise level.

The aforementioned concave groove may be provided approximately in the center of the heel portion along the main groove of the drill over a length from the cut-up part of the main groove to the vicinity of the tip of the drill, but this reduces the rigidity of the drill, that is, the mechanical strength. In order to reduce vibration and noise without
The groove shape has a width of 115 to 1/ of the width H of the heel part.
It is preferable to keep the depth at 0.1 to 0.2 D, which is the diameter of the drill, and the length to 0.8 to 0.9 L, which is the length of the blade.

Further, it is preferable that the shape of the groove is U-shaped so that stress concentration is less likely to occur.

That is, if the dimensions are greater than the above-mentioned limit, the drill will lack rigidity, and if the dimensions are less than the limit, the vibration and noise damping effect will be reduced.

As described in detail above, the noise level can be reduced simply by providing the groove in the heel portion, making it possible to prevent noise without affecting the cutting performance of the drill in any way.

[Brief explanation of drawings]

Fig. 1 shows the stress distribution in the cross section of a deep hole drill, Fig. 2 is a front view of the deep hole drill according to the present invention, and Fig. 3 shows frequency analysis during drilling with a conventional deep hole drill. Figure 4 shows the results of frequency analysis during drilling with the deep hole drill according to the present invention; Figure 5a shows the natural frequency measurement results of the conventional deep hole drill; The figure shows the natural vibration measurement results of the deep hole drill according to the present invention. 1: Heel part, 2 Nitrile main groove, 3: Deep hole drill body, 4: Handle sound\5: Blade part, 6: Concave groove.

Claims (1)

[Scope of Claims] 1. In a deep hole drill having a uniform cross-sectional shape over the entire length of the blade, a length extending along the drill main groove from the cut-up part of the drill main groove to near the tip of the drill is located approximately at the center of the heel portion. A deep hole drill characterized by having a concave groove extending all the way. 2. In a deep hole drill having a uniform cross-sectional shape over the entire length of the blade, there is a hole located approximately in the center of the heel portion along the drill main groove with a width of 115 to 1/3H of the width H of the heel portion and a depth of the drill diameter. A drill for deep holes, characterized in that a concave groove of 0.1 to 0.2D is provided over a length of the blade length of 018 to 0.9L from the cut-up part of the drill main groove.