Wipe out project tool marks

It happens to the best of us, but by following a few simple precautions, you can remove the goofs before they pose a problem. Begin with sound machining, assembly, and prep practices, relying on the handy Tool-Mark Problem Solver for specific fixes.

Tool marks leave an uneven surface on the wood, change its color, and alter the way it absorbs a stain or finish. Once a stain or finish goes on, most tool marks are pretty much there to stay, unless you sand back down to bare wood. The ultimate strategy for eliminating tool marks is prevention, with final touch-ups serving as backup.

Preventing tool marks starts by using only sharp and clean bits, blades, and other cutters on your machines, and running these at the proper speed. Align your tablesaw fence parallel to the blade. Also, mill all pieces of stock slightly oversize, observing how well the wood machines, and adjusting feed rates and direction to get the best cut. Finally, "sneak up" on the final cut, taking off just a small amount of material. Doing this will clean up existing tool marks without creating new ones.

Many believe power-sanding cures a world of ills, and it can. But it also can cause its own set of tool-mark problems. Take care here or you'll risk the hard work you spent building the project.

First, wipe down all the surfaces you plan to sand with a tack rag to remove sawdust and other debris that can make scratches when they are picked up by the sander. Then, move up through the sandpaper grits in small steps from coarse to fine and let the sander do the work, wiping down the piece between each grit change.

Next, use a soft cloth to apply mineral spirits to all the areas you sanded. The "mineral spirits rubdown," shown below, offers three benefits—t gives you an idea what the wood will look like under a clear finish, shows up glue stains you may have missed, and highlights any remaining tool marks, including notoriously hard-to-see sanding swirls. Note the spots that need more work and go back to them after the mineral spirits dries. This trick also can be used prior to assembly or during dry-fitting to find problems that would be difficult to repair after assembly.

For the ultimate surface, complete the process with a final hand-sanding at 220grit (or up to one step higher than your last machine grade), following the direction of the wood's grain. Despite advances in sanding technology, nothing produces a mar-free surface like patient hand-sanding under an attentive eye. And one last check with mineral spirits will ensure no surprises at finish time. What should you do if you apply a stain or finish and a tool mark bids hello? Simple: Reach for the sandpaper once more and a hefty can of elbow grease.

Though not typically caused by tools, dents and scratches in wood also can show up at finish time like uninvited guests. And while sanding removes surface scratches, dents require a different tack. First, moisten the dented area by placing a damp cloth over the depression, and then running a hot household iron over the cloth, as shown below. The steam generated will swell the compressed wood fibers, letting you sand them flush once they dry.

Sometimes, the easiest and best fix for tool marks is to mill a replacement part, or better yet, to machine extra stock for spares in the beginning. Another option includes using tool-marked stock in areas where it won't be seen.

December/January 2005/2006