L₄—total length of brazed step drill; l₄— length of the working part of brazed step drill; d₄—substrate diameter of brazed step drill; β₄—helix angle of brazed step drill; l₀₄— drilling part; d₀₄— diameter of drilling part; 2Φ₄— apex angle of brazed step drill; γ₄— front angle of brazed step drill (N₄—N₄ profile); α₄— back angle of brazed step drill (O₄—O₄ profile); l₁₄— transition part; l₂₄— reaming part; H₄—line spacing of diamond abrasive particles of brazed step drill; h₄—space between diamond rows of brazed step drill; h_t4—protrusion height of single abrasive particle of brazed step drill; D₄— mean diameter of brazed step drill.Fig. (5) Geometric structure of Brazed step drill.