A method for manufacturing a tool head (1, 30) of a rotary cutting tool, the tool head (1, 30) having a front end (10, 42) and a rear end (26, 31) between which a centre axis of rotation and a peripheral envelope surface (7, 37) extend, the method comprising: - forming at least a first part (4, 34) and a second part (4', 34') from a powder composition, wherein the powder composition is a hard metal composition or a cermet powder composition, wherein the first part (4, 34) comprises a first joining surface (5, 35) and wherein the second part (4', 34') comprises a second joining surface, the first joining surface (5, 35) being configured to be brought into contact with the second joining surface, wherein the first part (4, 34) further comprises a first outer surface portion (6, 36) configured to form a first portion of the peripheral envelope surface (7, 37) of the tool head (1, 30), and wherein the second part (4', 34') further comprises a second outer surface portion (6', 36') configured to form a second portion of the peripheral envelope surface (7, 37) of the tool head (1, 30), - forming at least one groove (15, 17, 18, 38, 40) in the first joining surface (5, 35) and at least one corresponding groove in the second joining surface, wherein the at least one groove (15, 17, 18, 38, 40) of the first joining surface (5, 35) is configured to face the at least one corresponding groove of the second joining surface when the first joining surface (5, 35) and the second joining surface are brought into contact, comprising forming the at least one groove (15, 17, 18, 38, 40) as a curved groove, - assembling the parts (4, 34, 4', 34') into a shape of a tool head (1, 30) by bringing at least the first and second joining surfaces (5, 35) into contact to form an interface, so that at least one pair of facing grooves (15, 17, 18, 38, 40) forms a channel (23, 24, 41) extending in the interface, the channel (23, 24, 41) having an inlet opening in the rear end (26, 31) of the tool head (1, 30) and an outlet opening in the front end (10, 42) and/or in the peripheral envelope surface (7, 37) of the tool head (1, 30), and the channel being curved in a plane parallel with the centre axis, - joining the assembled parts (4, 34, 4', 34') in a sintering operation to form the tool head (1, 30). - forming at least a first part (4, 34) and a second part (4', 34') from a powder composition, wherein the powder composition is a hard metal composition or a cermet powder composition, wherein the first part (4, 34) comprises a first joining surface (5, 35) and wherein the second part (4', 34') comprises a second joining surface, the first joining surface (5, 35) being configured to be brought into contact with the second joining surface, wherein the first part (4, 34) further comprises a first outer surface portion (6, 36) configured to form a first portion of the peripheral envelope surface (7, 37) of the tool head (1, 30), and wherein the second part (4', 34') further comprises a second outer surface portion (6', 36') configured to form a second portion of the peripheral envelope surface (7, 37) of the tool head (1, 30), - forming at least one groove (15, 17, 18, 38, 40) in the first joining surface (5, 35) and at least one corresponding groove in the second joining surface, wherein the at least one groove (15, 17, 18, 38, 40) of the first joining surface (5, 35) is configured to face the at least one corresponding groove of the second joining surface when the first joining surface (5, 35) and the second joining surface are brought into contact, comprising forming the at least one groove (15, 17, 18, 38, 40) as a curved groove, - assembling the parts (4, 34, 4', 34') into a shape of a tool head (1, 30) by bringing at least the first and second joining surfaces (5, 35) into contact to form an interface, so that at least one pair of facing grooves (15, 17, 18, 38, 40) forms a channel (23, 24, 41) extending in the interface, the channel (23, 24, 41) having an inlet opening in the rear end (26, 31) of the tool head (1, 30) and an outlet opening in the front end (10, 42) and/or in the peripheral envelope surface (7, 37) of the tool head (1, 30), and the channel being curved in a plane parallel with the centre axis, - joining the assembled parts (4, 34, 4', 34') in a sintering operation to form the tool head (1, 30).