Abstract: An apparatus for performing machining operations in poorly accessible locations includes a fastening head, which is held at one end of a shaft stub, while the other end is in engagement via a bevel gear drive with a drive shaft which is retained in a longitudinal housing. A longitudinally displaceable telescopic guide is provided on the longitudinal housing at right angles thereto. The telescopic guide is compressible counter to the pressure of a spring. A micrometer screw is provided for fine adjustment of the distance between the fastening head and the telescopic guide.

Abstract: A two-part navigational measurement device comprising a transparent circular disc having a coordinate grid thereon. An annular ring is coaxially positioned about the circular disc, the circular disc being rotatable within the annular ring. The annular ring has gradations around at least half of its circumference. A tangent ruler is fixed to the annular ring, the tangent ruler having a tangent edge which is tangent to the annular ring at the mid-point of the gradations. Means, such as a set screw may be provided for locking the disc and the annular ring against rotation relative to each other after the course to be adhered to has been determined.