Figure 18-12. A special insert, with a disk that is centered perfectly under the drum, is needed when the drum sander is used for pattern sanding.
Pattern sanding is done by making a special insert with a guide disk having a diameter equal to the drum's diameter (Figure 18-12). It is important that the disk be centered exactly under the drum; therefore, when making the insert, be sure to follow the instructions shown in Figure 18-13.
Figure 18-13. To make a special insert for pattern sanding, use a drum sander insert as a pattern. Locate the position of the guide disk with the drum sander mounted on the spindle. Attach the disk with glue and 1/2" brads. Click image to see larger view.
Figure 18-14. The pattern, with work attached, rides against the guide disk so the work is sanded to duplicate the shape of the pattern. Click on image to see larger view.
Figure 18-14 shows how the sanding is done. The pattern, which is the shape of the work you need, rides against the guide disk. The rough-cut work is held to the pattern with small brads or is impaled on brad points that project from the pattern. As you make the pass, keep the pattern in constant contact with the guide disk so that the work will be sanded to match the pattern.
Pattern sanding on the drum will work only if you accept it as a smoothing operation. When you rough-cut the workpieces, be sure they are not more than 1/16" or so oversize.