Abstract: If we want to manufacture smooth and evenly thick veneers, we must properly control and adjust the back angle of the lathe knife. In the existing technological literature available, no basic rules are pointed out and the related formulae offered are very difficult to be put to use. We analysed two kinds of knife carriages (three types) and found the basic rule concerning the effect of the changes of the back angle of the knife to be a = f(H). A simple method for adjusting the back angle of the knife, ie. the step by step measuring and regulating, has been devised. First, theconstant of the change of the back angle of the knife is to be determined; Then, the oblique angle of the second guide is to be determined and adjusted; Finally, adjust the situation of B to the designed destination.