Axes of rotation for platonic solids

The tetrahedron


The tetrahedron has rotational symmetries of order $2$ and $3$. The poles of order two are the midpoints of edges. The poles of order $3$ are the vertices, or the centres of the faces (which are opposite the vertices). The rotation group acts on the four vertices as the alternating group $A_4$. The full symmetric group $S_4$ also acts on the tetrahedron, but the odd permutations act by orthogonal matrices of determinant $-1$, which are not rotations. The transpositions act as reflections, but the $4$-cycles are more complicated.

The cube and octahedron


The cube and the octahedron have the same rotational symmetries, which have order $2$, $3$ or $4$. The poles of order $2$ are the midpoints of the edges of the cube, which are the same (up to rescaling) as the midpoints of the edges of the octahedron. The poles of order $3$ are the vertices of the cube, or the centres of the faces of the octahedron. The poles of order $4$ are the vertices of the octahedron, or the centres of the faces of the cube. The rotation group acts on the four long diagonals of the cube as the permutation group $S_4$.

The dodecahedron and icosahedron


The dodecahedron and the icosahedron have the same rotational symmetries, which have order $2$, $3$ or $5$. The poles of order $2$ are the midpoints of the edges of the dodecahedron, which are the same (up to rescaling) as the midpoints of the edges of the icosahedron. The poles of order $3$ are the vertices of the dodecahedron, or the centres of the faces of the icosahedron.. The poles of order $5$ are the vertices of the icosahedron, or the centres of the faces of the dodecahedron. The rotation group acts on the five inscribed cubes of the dodecahedron as the permutation group $S_4$.