A method of forming a core for use in casting a turbine engine component characterized in that: forming a normal resolution region of the core using a first process of molding; and forming a high resolution region of the core using lithographic molding, which is a method of molding different than the first process and effective to produce high resolution features; wherein the high resolution region has one or more high resolution features selected from the group consisting of a recess, cavity, opening, protrusion, channel, groove, slot, and depression; wherein the normal resolution region is defined by a first core piece and the high resolution region is defined by a second core piece; wherein the first core piece includes a cavity therein; wherein the second core piece includes a protrusion, joining the first and second core pieces (12, 14) such that a first portion of the protrusion is received in at least a portion of the cavity; heating the protrusion via an intermediate thermal heat treatment process causing the protrusion to thermally deform to create a three dimensional interlocking joint between the first and second core pieces (12, 14) by allowing thermal creep to irreversibly interlock the first and second core pieces (12, 14) together such that the joint becomes physically locked together providing joint stability through thermal processing; wherein the cavity is offset from a lateral contact surface such that the cavity is exposed through the first core piece via a neck having a cross-sectional area that is less than the cavity; and inserting a locking member into the cavity housing the protrusion and into at least a portion of space in the cavity which was vacated by the protrusion once the protrusion was thermally deformed during the intermediate thermal heat treatment process. forming a normal resolution region of the core using a first process of molding; and forming a high resolution region of the core using lithographic molding, which is a method of molding different than the first process and effective to produce high resolution features; wherein the high resolution region has one or more high resolution features selected from the group consisting of a recess, cavity, opening, protrusion, channel, groove, slot, and depression; wherein the normal resolution region is defined by a first core piece and the high resolution region is defined by a second core piece; wherein the first core piece includes a cavity therein; wherein the second core piece includes a protrusion, joining the first and second core pieces (12, 14) such that a first portion of the protrusion is received in at least a portion of the cavity; heating the protrusion via an intermediate thermal heat treatment process causing the protrusion to thermally deform to create a three dimensional interlocking joint between the first and second core pieces (12, 14) by allowing thermal creep to irreversibly interlock the first and second core pieces (12, 14) together such that the joint becomes physically locked together providing joint stability through thermal processing; wherein the cavity is offset from a lateral contact surface such that the cavity is exposed through the first core piece via a neck having a cross-sectional area that is less than the cavity; and inserting a locking member into the cavity housing the protrusion and into at least a portion of space in the cavity which was vacated by the protrusion once the protrusion was thermally deformed during the intermediate thermal heat treatment process.