A pump cylinder housing has a hollow cylinder and an end-side cover part, a threaded sleeve may be fixed on the outside of the hollow cylinder, at least three radially outward projections are connected to and distributed on the cover part periphery to the cover part and at least partly pass through recesses of the threaded sleeve. A union nut may be screwed onto the threaded sleeve so that the projections project radially out of the threaded sleeve and bear on an end side of the union nut. The cylinder housing may be assembled by in a simple manner so that the cylinder housing and the cover part may be connected to one another in an exactly colinear and centred manner and thereby may be reliably sealed. The cylinder cover may thereby be positioned in an infinite radial position on the cylinder.