Tool adaptor and combination with tool

A combination of a tool adaptor and a tool comprising:

• the tool adaptor comprising:
• a body defining a first end and a second end opposite to the first end along a longitudinal axis, wherein the body is provided with a connecting hole extended along the longitudinal axis, and an engaging hole extended along a radial direction of the longitudinal axis, wherein the connecting hole at least penetrates the first end, and wherein the engaging hole communicates with the connecting hole;
• a sleeve slidably mounted around the body along the longitudinal axis, wherein the sleeve is provided with a pressing portion protruding from an inner side wall surface of the sleeve;
• an elastic member elastically abutting against the body and the sleeve;
• at least one engaging ball movably disposed in the engaging hole along the radial direction of the longitudinal axis;
• and
• the tool detachably connected to the connecting hole and having an engaging groove;
• wherein the at least one engaging ball is selectively pressed by the pressing portion as the sleeve slides relative to the body, so as to enter the connecting hole and to engage with the engaging groove of the tool;
• wherein a size of the at least one engaging ball is configured such that when the at least one engaging ball enters the connecting hole, a clearance is formed between an outer periphery of the at least one engaging ball and a groove bottom face of the engaging groove.