A review of machining damage effects in beryllium was made. Surface damage is caused by twinning and microcracking as a result of various machining operations. Twinning is a result of surface working while microcracks initiate at intersections of twins and grain boundaries, at twin-matrix interfaces, at impurity particles, and in heavily twinned regions. These phenomena may be due to residual stresses in wrought products as well as machining parameters such as tool type, feed, and speed and depth of cut. The loss of mechanical properties due to machining damage is reviewed. Also presented is a study of surface damage actually encountered with machining of the shingles for the Gemini spacecraft.

The memorandum summarizes current knowledge concerning the machining of titanium alloys. The memorandum deals with the following conventional machining operations: milling, face milling, peripheral milling, turning, boring, drilling, tapping, and grinding. The last section of the memorandum deals with chemical milling operations.