| 摘要 |
An improved circle drawing tool is equipped with a doughnut-shaped outer board, a circular slide track mounted onto the outer board and an inner circular board provided with rolling balls in a plurality of receiving cavities thereof and having such a diameter that it can be rotarily engaged with the slide track as well as the doughnut-shaped outer board in assembly. On the doughnut shaped outer board are disposed a plurality of round holes distributed one by one consecutively according to their diameters. The are 4 straight lines separated apart at 90 degrees in angle. There are a number of small pen insertion holes consecutively spaced by 4 mm on each line and each starting point of the four lines is 1 mm farther away from the center of the outer board. There are 10 radial lines equally divided on the inner circular board. On each radial line there are a plurality of consecutive pen insertion holes defined thereon with every two neighboring points 10 mm spaced apart. Each starting point of all the 10 lines is 1 mm farther away consecutively from the center of the circular board so as to make the pen insertion holes distributed within a certain range in 1 mm divisional level. An extension arm having a plurality of pen insertion holes can be connected to the rotary outer board so as to permit circles larger than the diameter of the outer board can be drawn.
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