The F-atom reaction with NH3 and ND3 has been studied using the universal crossed beams technique. Angular resolved time-of-flight spectra were measured for the HF and DF reaction products. Product angular distribution and product kinetic energy distribution in the center-of-mass frame were determined from the experimental TOF spectra. Experimental results show that the HF and DF products are largely forward-scattered relative to the F-atom beam direction with a considerable amount of product at sideway and backward scattering directions. High-level ab initio calculation on the reaction energy pathway suggests that the forward-scattered products are mainly produced via a direct abstraction mechanism at large impact parameters, whereas sideway- and backward-scattered products are likely due to a long-lived complex formation mechanism.