The main purpose of thermal friction drilling is to increase the connection strength with the help of bushing formation. Therefore, the bushing formation and its geometry are of great interest. In this study, the bushing shapes obtained from the literature are analyzed geometrically according to their outer curve lines. These curve lines resemble a graph of parabola with varying slopes. The total volume of the evacuated material is completed when the tool cylindrical region sinks into the workpiece (t) mm in depth. It is accepted that approximately by the time when the tip of the tool reaches the half thickness of the material, the evacuated material forms a flake. By subtracting the flake volume (VC) from the total evacuated-material volume (VE), the volume of the bushing shape (VB) is determined. From the obtained equation, the bushing height is found, depending on the hole diameter (d), sheet-material thickness (t), tool conical angle (b), feed rate (f), which can be selected by the operator, and also equation constant μ. Using the bushing-height values, gained from the literature, the limit of the constant is specified as 0.001 £ μ £ 1.2 for thermal friction drilling of all kinds of materials. By comparing the experimental bushing-height results, obtained from the literature, with the modeling data, it is observed that the equation constant (μ) shows a simultaneous alteration with the material thickness (t), hole diameter (d) and tool conical angle (b), but an adverse alteration with the feed rate (f).Glavni namen termi~nega tornega vrtanja je pove~anje vezne trdnosti med osnovnim materialom in med vrtanjem za vrtino nastalo posebno obliko (blazinico). Zato sta nastanek te blazinice za vrtino in njena geometrija zelo zanimiva. Avtorji geometri~no analizirajo blazinice, nastale po tornem vrtanju, glede na njihov zunanji obris. Podatke o njihovih geometrijah so zbrali v podani literaturi. Obrisi nastalih blazinic spominjajo na parabole z razli~nim nagibom. Pretvorba izvrtanega materiala v blazinico se zaklju~i, ko se cilindri~ni del vrtala potopi v material za globino (t) v mm. Splo{no je sprejeto, da dokler konica vrtala ne dose`e pribli`no polovice debeline materiala, izvrtani material tvori obliko ostru`ka. Z od{tevanjem volumna ostru`ka (VC) od celotnega volumna (VE) lahko izra~unamo volumen nastale blazinice (VB). Vi{ino nastale blazinice lahko tako izra~unamo v odvisnosti od premera vrtine (d), debeline materiala (t), kota konice vrtala (b), hitrosti prodiranja vrtala v material (f), ki jo dolo~i/izbere operater na stroju in konstante μ. Iz podatkov, zbranih v literaturi za nastale vi{ine blazinic, ima konstanta vrednosti med 0.001 £ μ £ 1.2 za termi~no vrtanje vseh vrst materialov. Primerjava eksperimentalnih rezultatov za vi{ino blazinice, dobljenih v literaturi, z modelnimi podatki ka`e, da je konstanta (μ) isto~asno odvisna od debeline materiala (t), premera vrtine (d), koni~nosti konice vrtala (b), medtem ko ima hitrost prodiranja vrtala v material (f) obraten u~inek. Klju~ne besede: termi~no torno v...