NEW FAMILY MEMBER - continuation

DRILL CZ005    NEW FAMILY MEMBER

Continuation of the previous article

WE DO NOT TRY TO IMPROOVE SOLUTIONS WE HAVE ALREADY KNOWN BUT WE DO IT DIFFERENTLY FROM THE VERY BEGINNING TO REACH OUR GOAL: CUTTING SPEED v=30-35 m/min, feed f = (0,016 – 0,020) x D (mm/res.) (D = drill diameter in mm).

The geometry of the new CZ005 drill is based on the principle of an extremely thin core, which significantly reduces both axial force (up to 60%) and torque (up to 30%). This was verified both by tests and measurements of drills CZ002 and CZ004 at Brno University of Technology already in 2007, and by the deployment of more than 2,300,000 pieces of these drills in practice in companies.

The nominal diameter of the CZ005 drill was chosen within a tolerance of ⌀ Dh8 and its length dimensions (total length and slot length) were selected according to DIN 338, ie "medium length series", with regard to the largest anticipated use of CZ005 for drilling holes up to 3 x D. To ensure the rigidity of the CZ005 drill, its core is made in three mutually adjoining sections.

The first section with a core diameter (0.06 ÷ 0.08) x D (mm) in the length (1 ÷ 1.5) x D from the tip of the drill is constant and significantly reduces both axial force and torque and thus significantly reduces heat development at the place of its greatest origin. In addition, this extremely thin core, in combination with the advantageous profile and the groove angle of the drill, simultaneously extends the length of its main blade and the positive values ​​of the main blade face angle are thus maximally shifted towards the center of the drill. This solution not only enlarges the part of the drill that cuts and reduces the part of the drill (in its center) that only forms and pushes the material towards its main blade, but also gives the possibility of regrinding the drill while maintaining its original geometry.
The second section of the core in the length (4 ÷ 5) x D made with an increase to (0.25 - 0.35) x D guarantees high rigidity of the CZ005 drill in its working part. The third, last section of the drill core with an increase to (0.4 - 0.5) x D at the end of its groove guarantees high rigidity of the drill close to its clamping. The profile of the drill groove, the transition to the dorsal part of which is made by a chamfered edge (not a radius) together with the choice of the geometry of its tip, was chosen so that the chip is formed into the most advantageous shape allowing its fastest removal from the cut. The geometry of the drill ridge was chosen on the principle of a multi-faceted design of the so-called "roof cut", which guarantees a constant ridge angle along the entire length of the main blade. In addition, this cut is made in three stages, which not only has a significant effect on reducing heat generation due to friction of the drill bit against the bottom of the drilled hole (shape memory of stainless steels is generally known), but also allows the maximum amount of coolant to be supplied to the cut.

MAIN BLADE GEOMETRY IS REVOLUTIONARY

The original solution is the design of the first part of the cut of the CZ005 drill ridge, which creates a chamfer, the width of which in the center of the drill corresponds to the core diameter. veneers (0.03 - 0.04) x D lining the drill groove. This significantly reduces the friction between the chamfer on the back of the drill and the surface of the bottom of the drilled hole due to the increasing cutting speed along the main blade towards the nominal ⌀D of the drill. The design of the main blade, which in the first 2/3 of its length from the center of the drill passes along a convex curve to the axis of the drill so as to continue its last 1/3 in its axis, thus meets the requirement that the vector of the resulting cutting force as a tangent to the circle around the center of the drill at the appropriate point of the main blade, where the highest cutting speed is, made an ideal angle of 90º with the plane passing through the axis of the drill. In addition, the main blade in the section of the first 2/3 from the center of the drill creates an advantageous angle that the main and transverse blades form, thus creating favorable conditions for drilling the CZ005 drill and thus drilling a very precise hole. In addition, this main blade geometry solution allows the selection of an extreme drill bit angle greater than 140º, which significantly reduces both axial force and torque while maintaining high geometric accuracy of the drilled holes. This design of the main blade in combination with the extremely thin core and the preferably selected groove profile also creates very good conditions for the cutting process, which begins right at the center of the drill, thus minimizing the drill bit face that does not cut but only extrudes into the material. This has a significant effect not only on the centering of the drill, but especially on a significant reduction in heat generation during the drilling process and thus a substantial increase in its performance and extension of its durability and life.

You will find the test results of the first prototypes of the CZ005 drills in the next article.

NÁSTROJE CZ, s.r.o., Riegrova 399/2, 697 01 Kyjov
Obchodní kancelář Dobruška: Křovická 1047, 518 01 Dobruška; Tel.: +420 491 615 785; GSM: +420 777 581 299; E-mail: objednavky@nastrojecz.cz; URL: obchod.nastrojecz.cz