Sanding secrets

Sanding is both a plague for woodworkers and an essential ingredient of great craftsmanship. You may get everything else right, but if you mess up on the sanding, your project will be second-rate.

Unfortunately, necessity doesn’t make the job fun–it’s easy to lose enthusiasm when you’re covered in sawdust. The key to sanding well is to get the work done as efficiently as possible. And to make that happen, you need the right attitude, equipment and techniques.

Sanding might seem like the final step in a project, but it’s not. The bulk of effective sanding happens at the beginning and middle stages of construction. By the time your project is assembled, you can’t do much more than ease corners and fix up small dings.

I always start sanding my stock after rough-cutting parts to length and width. No matter how smooth a piece of wood seems, don’t be fooled. It still needs to be sanded. Marks left behind by the planer may seem almost invisible at first, but they really jump out when covered by a finish–especially dark stains.

If I’m using finely planed softwood, I’ll complete my initial sanding using a 120-grit disc in a random-orbit sander; make that 80-grit for hardwoods. If the wood surface is noticeably scalloped because it was milled with a poorly tuned thickness planer, use a belt sander oriented in the same direction as the wood grain and the same abrasive grits.

One exception to this rule is when you’re levelling an edge-glued solid wood panel. Sand at 90º to the grain until all the joints are level, then continue to sand parallel to the grain to remove cross-grain scratches. Regardless of the sander or situation, the objective is the same: remove all traces of milling marks. There’s no point in making the wood really smooth now, though. It’s almost certain to get dinged up as you continue working.

Complete the second stage of sanding after the parts are cut to length, once joinery features such as dados, rabbets or biscuit slots are complete. This is the time to bring surfaces to the next level, and a random-orbit sander is the ideal tool, whether you’re using hardwoods or softwoods. Just be sure to increase only one grit level finer from what you used during the first stage. Work the sander back and forth along the grain using light hand pressure.

 

Ordinary overhead shop lights are rarely adequate to reveal the areas you may have missed with the sander. But a 500-watt quartz-halogen floodlight shining across wood surfaces at a shallow angle makes it easy to see those spots.

Test-fit your project without glue, then take it apart and give the components a final sanding with a 180-grit abrasive for hardwoods and 220-grit for softwoods. A little work rounding the corners of the assembled item with a piece of 220-grit paper, and you’re ready to clean up the dust with a vacuum and finish your ultra-smooth project. Now, that wasn’t so bad after all, was it?

Face frames

Woodworking projects often include a framework of narrow stiles and rails fastened to the front of cabinet openings. These face frames always have corners with intersecting grain directions. How do you smooth these opposing pieces of wood without making cross-grain scratches? You don’t–at least, not at first.

If stiles and rails form face-frame corner joints that are more than 1/32" uneven, level them with a belt sander spinning a 100-grit abrasive in a two-step process. Start by sanding across the grain, right over the ends of the stiles, until the joint is level. Next, rotate the belt sander 90º and remove cross-grain scratching created during the first step. Finish up with a very light sanding over the joint, using a 180-grit disk in a random-orbit sander, and you’re done.

Smoothing profiles

Factory-milled moulding and trim are the most challenging items to sand properly because of their curved shapes and the prominence of milling marks often found on the surface. Hand-sanding removes these flaws, but it takes a lot of work and time. It’s not easy to maintain the enthusiasm required to complete the sanding on these consistently, unless you have some help.

My favourite tool for power-sanding irregular surfaces is an item developed in Canada nine years ago called a sanding mop. Cloth-backed discs of sandpaper are mounted on a mandrel that you can chuck in a handheld drill or drillpress. Spin the sanding mop at about 3,000 rpm, and it’ll smooth all kinds of profiles and contours without rounding over crisp edges. A wider version of this item is made for sanding wider trim on a shop-built table.