Method of assembling a connecting device on a stripped end section of an electric cable, said connecting device comprising a conducting element having a tubular portion and an insertion opening through which it is intended to introduce said stripped end section into said tubular portion, said method comprising the steps of: - supplying a said connecting device and a said electric cable; - introducing said stripped end section into said tubular portion via said insertion opening; - securely assembling said tubular portion on said stripped end section; said method being characterized in that said step of securely assembling comprises: - a first step of crimping a first zone of said tubular portion with a first portion of said stripped end section that is located in said first zone, which first zone being farthest from said insertion opening, said first crimping step being configured so that said first crimped portion of said stripped end section has a first predetermined degree of compression, said first step of crimping being configured so that the first zone and the first crimped portion have a compactness having a ratio of external perimeter of the first zone and the first portion to the smallest height passing through a centre of gravity of the first zone and the first portion which is less than about 6; - a second step of crimping a second zone of said tubular portion with a second portion of said stripped end section that is located in said second zone, which second zone being closest to said insertion opening, said second crimping step being configured so that said second portion of said stripped end section has a second predetermined degree of compression lower than said first predetermined degree of compression, said second step of crimping being configured so that the second zone and the second crimped portion have a compactness having a ratio of external perimeter of the second zone and the second portion to the smallest height passing through a centre of gravity of the second zone and the second portion which is less than about 6; - a step of punching a third zone of said tubular portion with a third portion of said stripped end section that is located in said third zone, which third zone being between said first and second zones (40, 41), said punching step being configured so that said third portion of said stripped end section has a third predetermined degree of compression higher than said first predetermined degree of compression, said step of punching being configured so that the third zone and the third punched portion have a compactness having a ratio of external perimeter of the third zone and the third portion to the smallest height passing through a centre of gravity of the third zone and the third portion which is greater than about 6. - supplying a said connecting device and a said electric cable; - introducing said stripped end section into said tubular portion via said insertion opening; - securely assembling said tubular portion on said stripped end section; - a first step of crimping a first zone of said tubular portion with a first portion of said stripped end section that is located in said first zone, which first zone being farthest from said insertion opening, said first crimping step being configured so that said first crimped portion of said stripped end section has a first predetermined degree of compression, said first step of crimping being configured so that the first zone and the first crimped portion have a compactness having a ratio of external perimeter of the first zone and the first portion to the smallest height passing through a centre of gravity of the first zone and the first portion which is less than about 6; - a second step of crimping a second zone of said tubular portion with a second portion of said stripped end section that is located in said second zone, which second zone being closest to said insertion opening, said second crimping step being configured so that said second portion of said stripped end section has a second predetermined degree of compression lower than said first predetermined degree of compression, said second step of crimping being configured so that the second zone and the second crimped portion have a compactness having a ratio of external perimeter of the second zone and the second portion to the smallest height passing through a centre of gravity of the second zone and the second portion which is less than about 6; - a step of punching a third zone of said tubular portion with a third portion of said stripped end section that is located in said third zone, which third zone being between said first and second zones (40, 41), said punching step being configured so that said third portion of said stripped end section has a third predetermined degree of compression higher than said first predetermined degree of compression, said step of punching being configured so that the third zone and the third punched portion have a compactness having a ratio of external perimeter of the third zone and the third portion to the smallest height passing through a centre of gravity of the third zone and the third portion which is greater than about 6.