A method of manufacturing spectacle arms, comprising the following steps of: - grooving an inner face of a first cover plate, so as to form several grooves in said inner face extending parallel and spaced apart one after the other; - providing a gauge comprising: - several longilineal inserts extending parallel and spaced apart one after the other and having respective front and rear (31, 32) ends; - a front bridge joining the front ends of all the longilineal inserts and having front indexing means disposed between the longilineal inserts; - a rear bridge joining the rear ends of all the longilineal inserts and having rear indexing means disposed between the longilineal inserts; - setting the gauge on the inner face of the first cover plate, so that all the longilineal inserts are disposed inside the grooves and that the front and rear bridges (33, 35) protrude from the first cover plate; - pressing and bonding a second cover plate on the inner face of the first cover plate, so that the longilineal inserts are inserted between the first cover plate and the second cover plate and that the front and rear bridges (33, 35) protrude from the first cover plate and the second cover plate; - cutting the first cover plate and the second cover plate by means of a cutting tool around the longilineal inserts in order to form spectacle arms, wherein the cutting tool, prior to cutting around a longilineal insert, is positioned and held in place with respect to said longilineal insert by cooperating with front indexing means and rear indexing means adjacent to said longilineal insert. - grooving an inner face of a first cover plate, so as to form several grooves in said inner face extending parallel and spaced apart one after the other; - providing a gauge comprising: - several longilineal inserts extending parallel and spaced apart one after the other and having respective front and rear (31, 32) ends; - a front bridge joining the front ends of all the longilineal inserts and having front indexing means disposed between the longilineal inserts; - a rear bridge joining the rear ends of all the longilineal inserts and having rear indexing means disposed between the longilineal inserts; - several longilineal inserts extending parallel and spaced apart one after the other and having respective front and rear (31, 32) ends; - a front bridge joining the front ends of all the longilineal inserts and having front indexing means disposed between the longilineal inserts; - a rear bridge joining the rear ends of all the longilineal inserts and having rear indexing means disposed between the longilineal inserts; - setting the gauge on the inner face of the first cover plate, so that all the longilineal inserts are disposed inside the grooves and that the front and rear bridges (33, 35) protrude from the first cover plate; - pressing and bonding a second cover plate on the inner face of the first cover plate, so that the longilineal inserts are inserted between the first cover plate and the second cover plate and that the front and rear bridges (33, 35) protrude from the first cover plate and the second cover plate; - cutting the first cover plate and the second cover plate by means of a cutting tool around the longilineal inserts in order to form spectacle arms, wherein the cutting tool, prior to cutting around a longilineal insert, is positioned and held in place with respect to said longilineal insert by cooperating with front indexing means and rear indexing means adjacent to said longilineal insert.