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How to Sand Wood Trim

Wood trims, such as wall moldings, require fine sanding to accept the high gloss finishes that are typically used for trim pieces. The profile detail of most wood trim prevents the use of efficient power sanders, such as random orbit and belt sanders. While detail sanders can be used, they are designed for small areas and add a lot of time to the project. Creating a custom wood sanding block is the best solution and will guarantee a quality sanding every time.

The intricate shapes of wood trim molding make sanding difficult.

Step 1

Miter cut a 1-inch piece of your trim off at a 90 degree angle. Position the end of the trim on a block of hardwood lumber 3 inches long and wide enough to cover the whole width of the trim. Trace the profile onto the end of the block with it standing with the 3-inch length upright.

Step 2

Cut the profile into your block with a band saw to create a 3-inch long section, that is a negative, or reverse profile of your molding. Cut a piece of 150-grit sandpaper long enough to fold into the profile on your block 3 inches wide. Apply spray adhesive to the back of the sandpaper and stick it to the profile face, folding it into the details of the profile. Sand down the length of the trim, then replace the paper with 220-grit sandpaper, and sand down the length of the trim again.

Step 3

Sand the trim with the block working from one end. Fit the block into the profile to match it and sand all faces of the profile at once. Work the block in line with the grain, with long back-and-forth strokes. Move down the trim, overlapping your strokes for adequate coverage.

Step 4

Peel used paper from the block and replace it in the same way to keep fresh paper. Create a separate block for each profile of molding you are sanding. Keep the blocks for reuse if you are planning to install the same molding profile again.