A method of threading a metal substrate on a rolling mill comprising: receiving a coil of the metal substrate ; uncoiling the metal substrate from the coil ; and guiding the metal substrate to a work stand of the rolling mill with a threading system , wherein guiding the metal substrate to the work stand comprises: guiding the metal substrate to a threading carriage of the threading system ; gripping the metal substrate with the threading carriage ; and moving the threading carriage towards the work stand , wherein the threading carriage comprises a pair of gripping rolls , and wherein gripping the metal substrate with the threading carriage comprises directing the metal substrate between the pair of gripping rolls and gripping the metal substrate with the gripping rolls , wherein the pair of gripping rolls grip the metal substrate at a position that is offset from a leading edge of the metal substrate such that when the leading edge is fed into a roll gap of the work stand , the threading carriage is spaced apart from work rolls of the work stand , characterized in that the method further comprises adding stiffness to the metal substrate by adding a diameter profile along a length of the gripping rolls such that the metal substrate comprises at least one lateral curvature across a width of the metal substrate . receiving a coil of the metal substrate ; uncoiling the metal substrate from the coil ; and guiding the metal substrate to a work stand of the rolling mill with a threading system , wherein guiding the metal substrate to the work stand comprises: guiding the metal substrate to a threading carriage of the threading system ; gripping the metal substrate with the threading carriage ; and moving the threading carriage towards the work stand , wherein the threading carriage comprises a pair of gripping rolls , and wherein gripping the metal substrate with the threading carriage comprises directing the metal substrate between the pair of gripping rolls and gripping the metal substrate with the gripping rolls , wherein the pair of gripping rolls grip the metal substrate at a position that is offset from a leading edge of the metal substrate such that when the leading edge is fed into a roll gap of the work stand , the threading carriage is spaced apart from work rolls of the work stand , characterized in that the method further comprises adding stiffness to the metal substrate by adding a diameter profile along a length of the gripping rolls such that the metal substrate comprises at least one lateral curvature across a width of the metal substrate . guiding the metal substrate to a threading carriage of the threading system ; gripping the metal substrate with the threading carriage ; and moving the threading carriage towards the work stand , wherein the threading carriage comprises a pair of gripping rolls , and wherein gripping the metal substrate with the threading carriage comprises directing the metal substrate between the pair of gripping rolls and gripping the metal substrate with the gripping rolls , wherein the pair of gripping rolls grip the metal substrate at a position that is offset from a leading edge of the metal substrate such that when the leading edge is fed into a roll gap of the work stand , the threading carriage is spaced apart from work rolls of the work stand , characterized in that the method further comprises adding stiffness to the metal substrate by adding a diameter profile along a length of the gripping rolls such that the metal substrate comprises at least one lateral curvature across a width of the metal substrate . <EOS>