A junction block for grounding comprising: - a conductive connection bar comprising a first orifice having a tapping with a determined diameter and intended to cooperate with the threading of a connection shunt, - a conductive stirrup intended to be mounted on a conductive support rail, said stirrup comprising a second orifice having a tapping with a diameter (D') smaller than or equal to the diameter of the tapping of the first orifice of the connection bar, - a conductive clamping screw arranged to clamp the stirrup on the support rail, the clamping screw comprising: - a head having a diameter greater than the diameter of the tapping of the first orifice of the connection bar, - a first portion extending from the screw head over a determined screw length, said first portion having a diameter (d) smaller than the diameter of the tapping of the first orifice of the connection bar so as to be able to slide freely in the first orifice, - a second portion extending from the first portion up to the end of the screw opposite to the screw head, said second portion having a threading with a diameter (d') substantially equal to the diameter (D') of the tapping of the second orifice of the stirrup, the length of the first portion being determined so that when the tapping of the second orifice of the stirrup cooperates with the threading of the second portion of the clamping screw then the tapping of the first orifice of the connection bar faces the first portion of the clamping screw. - a conductive connection bar comprising a first orifice having a tapping with a determined diameter and intended to cooperate with the threading of a connection shunt, - a conductive stirrup intended to be mounted on a conductive support rail, said stirrup comprising a second orifice having a tapping with a diameter (D') smaller than or equal to the diameter of the tapping of the first orifice of the connection bar, - a conductive clamping screw arranged to clamp the stirrup on the support rail, the clamping screw comprising: - a head having a diameter greater than the diameter of the tapping of the first orifice of the connection bar, - a first portion extending from the screw head over a determined screw length, said first portion having a diameter (d) smaller than the diameter of the tapping of the first orifice of the connection bar so as to be able to slide freely in the first orifice, - a second portion extending from the first portion up to the end of the screw opposite to the screw head, said second portion having a threading with a diameter (d') substantially equal to the diameter (D') of the tapping of the second orifice of the stirrup, the length of the first portion being determined so that when the tapping of the second orifice of the stirrup cooperates with the threading of the second portion of the clamping screw then the tapping of the first orifice of the connection bar faces the first portion of the clamping screw. - a head having a diameter greater than the diameter of the tapping of the first orifice of the connection bar, - a first portion extending from the screw head over a determined screw length, said first portion having a diameter (d) smaller than the diameter of the tapping of the first orifice of the connection bar so as to be able to slide freely in the first orifice, - a second portion extending from the first portion up to the end of the screw opposite to the screw head, said second portion having a threading with a diameter (d') substantially equal to the diameter (D') of the tapping of the second orifice of the stirrup, the length of the first portion being determined so that when the