We produced large binder-free multi-walled carbon nanotube (MWNT) blocks from fluorinated MWNTs using thermal heating and a compressing method in vacuo. This technique resulted in the formation of covalent MWNT networks generated by the introduction of sp(3)-hybridized carbon atoms that cross-link between nanotubes upon de-fluorination. The resulting carbon nanotube blocks are lighter than graphite, can be machined and polished, and possess average bending strengths of 102.2 MPa, a bending modulus of 15.4 GPa, and an electrical conductivity of 2.1 x 10(2) S/cm. Although each nanotube exhibits a random structure in these blocks, the mechanical properties are 3 times higher than those obtained for commercial graphite. On the basis of theoretical molecular dynamics simulations, a model is presented for the nanotube interconnecting mechanism upon de-fluorination.