A terahertz guided cutting tool will be built and tested.An initial brass board prototype will be built based on a commercial off the shelf (COTS) THz specialty coating thickness measurement system with handheld probe TeraMetrix has developed.This will be adaptable to both non-metallic straight blades and a metallic circular cutter.This system will be tested with various coupons to ensure cutting accuracy, ability to handle various features and areas of high curvature, comfortable and ergonomic use and maintainability.This will be followed by an alpha prototype customizing the handheld probe and incorporating lessons learned.The system will be lightweight (< 3lbs) and easy to use through a small touchscreen on the tool. In phase I, testing on relevant coatings and composite substrates has demonstrated thickness measurement with precision and accuracy < 1 mil.The THz method can measure coatings <<5 mils to >300 mils. The THz method does not exhibit thickness error in the presence of curved surfaces, fasteners or seams.