Acid delinting of cotton seed presents a personal safety and potential environmental hazard for cotton breeders. A means of delinting that does not use acid, but is effective at removing linters without adversely impacting germination is needed. A prototype mechanical cotton seed delinter was developed and built at the United States Department of Agriculture – Agricultural Research Service (USDA-ARS), Cotton Production and Processing Research Unit in Lubbock, Texas in order to optimize the mechanical process of delinting cotton seed. Testing evaluated seven drum linings, one or two roller brushes used for "scrubbing" lint from the cotton seed, and two processing times, five and ten min. The primary performance metrics evaluated were lint loss (i.e. residual lint remaining on the seed after processing) and germination. Other metrics such as visible mechanical damage of the seed and visual observations of durability and ease of clean out were also noted. Results revealed an alternating brush pattern of half nylon and half steel wire bristle brushes (42N42W) to be the best drum material using either one or two roller brushes at ten min of processing time. Lint loss values of the 42N42W material with one or two roller brushes at ten min were 0.95% and 0.88%, respectively. Germination rates for 42N42W at five and ten min were 89.3% and 88.4%, respectively. The 42N42W material appeared to be the most durable and was one of the easiest materials evaluated to clean out between samples. Based on findings in this study, a commercial unit for breeders was built by BC Supply in Lubbock, Texas. The findings of this study will be used in the development of a larger-scale model to process bulk quantities of seed during commercial production.