 Tangent command (Assembly environment)
  Tangent command (Assembly environment)
      Applies a tangent relationship between two parts in an assembly. You can apply a tangent relationship between a cylinder, cone, or torus, and a cylinder, cone, torus, or plane. For example, you can use a tangent relationship to ensure that the cylindrical face of one part in an assembly remains tangent to a planar face of another part.

Tangent part faces can touch each other or be offset from each other. When you define a fixed offset, you can type a value for the offset distance.