Abstract: Rolls for forming convoluted heat exchanger strips having louvers in the successive convolutions. The rolls comprise a series of axially stacked upper and lower discs having intermeshing gear-like teeth around their periphery for forming convolutions in a metal strip and for cutting and forming the louvers therein. The cutting teeth have their opposite side faces beveled, the beveled face on the leading side of the tooth extending radially outwardly from the area of the crotch between teeth through the tip of the tooth. On the trailing side of each tooth the beveled face extends radially outwardly from more closely adjacent the vertex of the crotch to a point short of the tooth tip.