The expanding use of materials that are difficult to join with traditional techniques drives an urgent need, in a wide array of industries, to develop and characterize production capable joining processes. Friction stir blind riveting (FSBR) is such a process. However, full adoption of FSBR requires more complete characterization of the process. The relatively inexpensive, portable FSBR machine discussed here facilitates in situ X-ray imaging of the FSBR process, which will enhance the ability of researchers to understand and improve the FSBR process. Real-time, unobstructed, angular X-ray access drives the functional requirements and design considerations of the machine. The acute angular access provided by the machine necessitates tradeoffs in stiffness and Abbe errors. An error budget quantifies the effect of the various trade-offs on likely sensitive directions and relationships. Additionally, the machine motivates more test parameters important to machine designers (e.g., parallelism and runout) that have not yet been explored in the literature. Ultimately, a machine has been developed, which has a single rotational axis that translates parallel to the rotational axis, can be built for under $12,000, has a mass of less than 110 kg, measures 915 mm × 254 mm × 624 mm, has a rotational speed range of 400–8000 RPM, has a feed rate range of 0.1–200 mm/min, can be installed on most test benches, has total rivet runout of 0.1 mm, has plunge and rotational axis parallelism of less than 0.1 deg, and has a plunge axis repeatability of better than 2 m over a 10 mm range.