New family member - continuation II.

DRILL CZ005 NEW FAMILY MEMBER

DRILL PROTOTYPE CZ005 WAS TESTED

The purpose of the first tests of the CZ005 drill was not only to verify the properties of its geometry to be achieved in the previous two editions, but especially to confirm the real possibility of achieving the target parameters: drilling at cutting speed v = 30-35 m / min at feed f = [(0.016-0.020) x D] mm / rev. (D = nominal drill Ø in mm).

For better forming and cutting ranges taking place during drilling in individual parts of the drill, especially in the area of ​​its tip, the diameter D = 13.00 mm was chosen for testing as the largest diameter of the considered production (2.00 - 13.00 mm). Fig. 1 shows the tip of the first prototype of the CZ005 drill.

Main parameters of the CZ005 drill:
    • nominal Ø D = 13.00 mm
    • total length L = 151 mm
    • helix length l = 101 mm
    • helix pitch angle λ = 29.9º
    • point angle Ɛ = 145º
    • ridge angle α on the 1st facet along the main blade = 14º
    • Core thickness:
        ◦ 1st section in the length of 13.00 mm - offer 0.90 mm
        ◦ 2nd section in the length of 58.00 mm - linear transmission to 3.8 mm
        ◦ 3rd section in the length of 30.00 mm - linear transmission to 4.6 mm
    • helix bevel width = 0.40 mm
    • high speed steel: 19852, M35
    • hardness: 66HRC

The drill was made of high-speed steel M35 commonly used in the production of drills for drilling stainless steels so that it was possible to evaluate only the effect of the new geometry on the drilling process. For better readability of forming and cutting processes (reflections, bruises), the drill was equipped with a commonly used TiAlN coating.

INITIAL CONDITIONS FOR THE TEST

    • drilled steel: austenitic stainless steel ČSN 417240, DIN 1.4301, X5CrNi 1810 (most used so-called food)
    • plate from rolled profile 200 x 120, 20 mm thick
    • through holes without drilling and pre-drilling, pitch 14.0 mm (8 rows x 14 holes = 112 holes)
    • testing machine: 4-axis CNC machining center HAAS VF2
    • coolant Quaker Cool 7350BFF, concentration 8%
    • clamping holder CZMK 3/13 with collet
    • cutting speed: v = 30, 36, 32 m / min
    • gradually speed: 735, 882, 784 rpm
    • feed f = 0.20 mm / rev, feed rate: 147, 176, 157 mm / min

In the first phase of testing, the cutting speed v = 30 m / min and the feed f = 0.20 mm / rev were chosen. After drilling 28 holes, the cutting speed was 36 m / min while maintaining a feed f = 0.20 mm / rev. After drilling another 28 holes, the cutting speed was reduced to 32 m / min while maintaining a feed f = 0.20 mm / rev. The drill behaved absolutely stably at all cutting speeds, which could be stated not only on the basis of its sound, but also on the basis of the % spindle load data, thus proving its ability to continue the drilling process. After drilling 126 additional holes, the drilling process was completed, especially with regard to maintaining the possibilities of diagnostics of forming - cutting processes and evaluation of its eventual wear.

AND THAT'S WHY WE CALL IT "FLASH BIT"

Fig. 2 is a front view of the tip of the CZ005 drill after drilling a total of 182 holes, drilling length = 3,640 mm. It is clear from the reflections that the drill starts to cut already in its center of the forming process, it is reduced to a small area in the second half of its transverse blade. This fact was also confirmed by measuring the chip width, which is the same as the length of the main blade. The wear along the main blade increases proportionally with increasing cutting speed without creating speeds.

The shape, integrity and quality of the chip surface (Fig. 3) also demonstrates the high rigidity, stability and cutting ability of the CZ005 drill from the very beginning of the drilling process (drilling into the material) to its end (starting from the material). The chip is formed in two main parts, which are separated after exceeding the value of the strength of its cross-section caused by the centrifugal force. The final phase of the chip in the shape of a "plug", created by extruding the bottom of the hole and then cutting it with the nominal Ø D of the drill, significantly protects its main blade from damage due to the drill coming out of the material. In addition, the edges of the holes are not pulled out - they do not have a "grot" slang.

The geometry of the holes (Fig. 4) and the quality of their surface also reach a very high quality. Inspection gauges showed that none of the 182 holes were larger than 0.025 mm.

Based on the first tests, it can already be stated that the CZ005 drill has all the realistic prerequisites to be among the most powerful drills in its category.
However, our company's development team still has a long way to go, not only completing the exact specification of geometric parameter values for each individual diameter from the entire production range of 2.00 - 13.00 mm, but also testing both the appropriate type of high-speed steel and the applied coating.

However, the first test results of the CZ005 drill are so surprising that a patent application was filed under the number PV 2021-445 to solve the geometry of its tip.