Square holes are characterized by high torque and good guidance. They are widely used in various industries, including aviation, aerospace, automobiles, and molding. In this study, a step-by-step electrical discharge machining (SSP) method was used to investigate the precision machining of square blind holes in a titanium alloy. This method integrates a limited set of multiple machining strategies with electrical discharge machining (EDM) by utilizing small shaped formed electrodes and step-by-step feeding for EDM. The main objective of this study was to investigate the machining efficiency and the surface quality of square blind holes in a titanium alloy. Two methods, EDM and SSP, were used to produce roughened circular pre-drilled components and square hole samples. Compared to EDM, SSP met the machining requirements of the square blind hole and improved machining efficiency by over three times, as well as surface quality by 16.06%. Subsequently, the influence of the machining area on precision machining was investigated, and a step-by-step precision machining process was established. Finally, two SSP methods, namely one-time SSP (O-SSP) and multiple SSP (M-SSP), were used for precision machining of rough-machined samples. Compared to O-SSP, M-SSP achieved higher machining accuracy and surface quality, despite its lower machining efficiency. The square hole, with a depth of 25 mm, was refined using M-SSP. It exhibited an upper and lower taper of 0.02 mm, a minimum fillet radius of R 0.04 mm, and a bottom corner radius of R 0.127 mm.
Highlights: A step-by-step electrical discharge machining (SSP) method was used to investigate the precision machining of square blind holes in titanium alloy.Both electrical discharge machining (EDM) and SSP methods were used to create roughened circular pre-drilled components and prepare square hole samples. Compared with EDM, SSP met the machining requirements of the square blind hole and improved machining efficiency by over threefold and surface quality by 16.06%.Two SSP methods, namely one-time SSP (O-SSP) and multiple SSP (M-SSP), were used for the precision machining of roughly machined samples. Compared with O-SSP, M-SSP achieved higher machining accuracy and surface quality, despite its lower machining efficiency. The square hole with a depth of 25 mm refined via M-SSP exhibited an upper and lower taper of 0.02 mm, a minimum fillet radius of R 0.04 mm, and a bottom corner radius of R 0.127 mm.