Piston pump for a vehicle brake system

A piston pump for a vehicle brake system, comprising:

• a pump housing (12);
• a check valve (52) having a valve seat (34);
• a piston (20, 22) that is driven to execute a reciprocating stroke motion and is axially displaceably received in said housing, the piston (20, 22) including a tubular deformed part (20), the inside of which forms a flow conduit (32, 36), which flow conduit admits fluid at one end of the tubular deformed part, and discharges fluid at the other end;
• the valve seat (34) of the check valve (52) is formed onto the tubular deformed part (20), wherein the check valve (52) prevents return flow of fluid through the flow conduit (32, 36);
• and the tubular deformed part (20) has a longitudinal groove, which groove forms the flow conduit (32, 36) at said one end of the tubular part;
• the piston (20, 22) also including a closure plug (22) which is joined to the tubular deformed part (20) at said one end, and substantially closes the tubular deformed part (20) at said one end;
• wherein the tubular part (20) is made by a cold forming process without any metal cutting or removing steps, such that the cold forming process hardens the surface of the tubular part and increases its dimensional stability and strength over what the part would have if shaped by a metal removing process.