Design is an important branch in Computer Aided Design. The automatic dimensioning in engineering draft of steelworks could improve the efficiency of the plant disign. During the developing steelworks design software

a practical algorithm to generate the dimensions on an engineering draft describing specific parts of the steel structure. As for a general engineering draft

the variety of part shapes

the complexity of illustration contents

the abnormality of layout and technical limitations make the automatic dimensioning seem too difficult to be realized. So a special algorithm to dimension joint draft in steelworks draft is proposed. This approach divides the margin of joint draft into eight zones:left top dimensioning zone

left dimensioning zone

left bottom dimensioning zone

top dimensioning zone etc. At the same time

a leader dimensioning algorithm is proposed. These approaches are feasible to generate the ordered dimensioning items for the disordered draft drawings. The algorithms have been applied in the PDSOFT Steelworks successfully.