Columnar hydraulic tappet

A columnar-type hydraulic tappet, provided with a housing (2), a plunger (1) moving axially with respect to the housing (2) being mounted in an inner cavity of the housing, a high pressure cavity (12) used for a hydraulic medium extending between a lower end surface of the plunger and a lower side of the housing, the high pressure cavity (12) being sealed by a unidirectional valve (3) opened towards the high pressure cavity (12), an outer ring groove (14) used for hydraulic medium circulation being arranged on the outer diameter of the housing, an inner ring groove (10) used for hydraulic medium circulation being arranged at a radial inner side of the housing (2), one or a plurality of oil inlet holes (9) being arranged between the inner ring groove (10) and the outer ring groove (14), a first ring groove (15) being arranged below a head portion of the plunger (13), a second ring groove being arranged at a central portion of the plunger, a plunger central wall being between the first ring groove (15) and the second ring groove, the second ring groove being a concave wide ring groove, wherein at least one plunger oil inlet hole (7) being arranged on the plunger concave wide ring groove (5) or the plunger central wall, a plunger oil inlet hole (7) is processed by a punch forming process in which the metal material flows into the cavity of the plunger to form a flanging (8) of the plunger oil inlet hole, and a bottom portion edge of the plunger oil inlet hole containing the flanging (8) facing towards an inner cavity of the plunger (1).