Abstract: In a securing element for connecting two parts, in particular for a screw connection, the securing element is ring-shaped. The securing element has an outer profile along the outer diameter and an inner profile along the inner diameter. The outer profile and the inner profile are both formed by a plurality of profile units. The number of profile units of the outer profile and the number of profile units of the inner profile correspond to the number of graduation marks at different scales according to the principle of a vernier scale, the number of profile units of the outer profile differing by at least 1 from the number of profile units of the inner profile. In precisely one position, a profile unit of the outer profile is exactly opposite a profile unit of the inner profile.

Abstract: A clamping system with a clamping nut and a wrench for tightening the clamping nut, wherein the clamping nut includes at least one recess on either the outside edge or the inside edge of the end face of the clamping nut to receive projections of the wrench. The edge opposite the edge with at least one recess is closed. The at least one recess is provided with at least one undercut, which the projections of the wrench can grip from underneath.

Abstract: A clamping system with a clamping nut and a wrench for tightening the clamping nut, wherein the clamping nut includes at least one recess on either the outside edge or the inside edge of the end face of the clamping nut to receive projections of the wrench. The edge opposite the edge with at least one recess is closed. The at least one recess is provided with at least one undercut, which the projections of the wrench can grip from underneath.

Abstract: A chuck for a tool with an inner cooling medium supply has a clamp holder having a cooling medium supply passage, a clamping nut anchorable in the clamp holder, and a ring-shaped sealing meter which is carried by the clamping nut and abuts against a clamped tool, the clamping nut having an outer concentric recess which surrounds the inserted tool and is formed so that the sealing member is exchangeably insertable from outside into the recess.