A new micromachining technique using user-defined trains of amplified femtosecond laser pulses is described. In this method, a 2-fold Michelson interferometer is used to split each output pulse of an amplified femtosecond laser system operating at 1 kHz into four different pulses at desired seperations ranging from 1 ps to 1 ns. These quadruple pulses are then focused on metal, semiconductor and dielectric samples and the material removal characteristics are noted. The experimental results show that there is a distinct effect of the pulse separation on the machining characteristics. It is observed that, in some cases, use of the quadruple pulses separated by 1 ns provides better material removal than the original pulses separated by 1 ms. The femtosecond laser-material interaction is also modeled for the case of metal samples using the two-temperature model. Numerical simulations that were carried out show that irradiation with quadruple pulses lead to a reduction in the predicted melting threshold fluence, which agrees with the experimental observation.