Use relations/mates to the existing standard three planes or Origin or a tangent mate in combination with others to your "round part" or you could also add some sketch geometry on existing planes or in a 3D sketch. Without more info it's hard to say, post your part or some images & someone can give you a better idea.
Use relations/mates to the existing standard three planes or Origin or a tangent mate in combination with others to your "round part" or you could also add some sketch geometry on existing planes or in a 3D sketch. Without more info it's hard to say, post your part or some images & someone can give you a better idea.