A method of making a part (10; 110; 210; 310) comprising a solid portion (14; 114; 214; 314) with an internal passage (16; 116; 216; 316), the method comprising: (a) building the part (10...310) using an additive manufacturing process by powder-bed fusion that builds the part (10...310) on a layer-by-layer basis, wherein building the part (10...310) comprises: i. fusing the solid portion (14... 314) of the part (10... 310); ii. forming a solid core (12; 12A-E; 112; 212; 312; 412) within at least a portion of the internal passage (16... 316), wherein forming the solid core (12...412) comprises: forming an attachment feature (20; 20A-E; 120; 320A-B), wherein forming the attachment feature (20... 320A-B) comprises forming at least one of a hole, bore, tongue, groove, receptacle, link, insert, chuck, socket, and clamp on the solid core (12...412); and forming a shearing feature (22; 22A-E; 322A-B); iii. positioning a material (18; 118; 218; 318) between the solid portion (14... 314) and the solid core (12...412), wherein the material (18...318) is semi-sintered or un-sintered; (b) applying a force selected from the group consisting of a compressive, pneumatic vibratory, and electric vibratory force to the solid core (12...412) at the attachment feature (20... 320A-B); and (c) shearing the material (18...318) positioned between the solid portion (14...314) and the solid core (12... 412) with the shearing feature (22... 416). (a) building the part (10...310) using an additive manufacturing process by powder-bed fusion that builds the part (10...310) on a layer-by-layer basis, wherein building the part (10...310) comprises: i. fusing the solid portion (14... 314) of the part (10... 310); ii. forming a solid core (12; 12A-E; 112; 212; 312; 412) within at least a portion of the internal passage (16... 316), wherein forming the solid core (12...412) comprises: forming an attachment feature (20; 20A-E; 120; 320A-B), wherein forming the attachment feature (20... 320A-B) comprises forming at least one of a hole, bore, tongue, groove, receptacle, link, insert, chuck, socket, and clamp on the solid core (12...412); and forming a shearing feature (22; 22A-E; 322A-B); iii. positioning a material (18; 118; 218; 318) between the solid portion (14... 314) and the solid core (12...412), wherein the material (18...318) is semi-sintered or un-sintered; i. fusing the solid portion (14... 314) of the part (10... 310); ii. forming a solid core (12; 12A-E; 112; 212; 312; 412) within at least a portion of the internal passage (16... 316), wherein forming the solid core (12...412) comprises: forming an attachment feature (20; 20A-E; 120; 320A-B), wherein forming the attachment feature (20... 320A-B) comprises forming at least one of a hole, bore, tongue, groove, receptacle, link, insert, chuck, socket, and clamp on the solid core (12...412); and forming a shearing feature (22; 22A-E; 322A-B); forming an attachment feature (20; 20A-E; 120; 320A-B), wherein forming the attachment feature (20... 320A-B) comprises forming at least one of a hole, bore, tongue, groove, receptacle, link, insert, chuck, socket, and clamp on the solid core (12...412); and forming a shearing feature (22; 22A-E; 322A-B); iii. positioning a material (18; 118; 218; 318) between the solid portion (14... 314) and the solid core (12...412), wherein the material (18...318) is semi-sintered or un-sintered; (b) applying a force selected from the group consisting of a compressive, pneumatic vibratory, and electric vibratory force to the solid core (12...412) at the attachment feature (20... 320A-B); and (c) shearing the material (18...318) positioned between the solid portion (14...314) and the solid core (12... 412) with the shearing feature (22... 416).