A lot of time in most woodworking projects is spent on the unglamorous task of sanding. Choosing and understanding the right wood sanding tools will greatly improve the efficiency and effectiveness of your efforts.
Being abrasive – in a good way
Far from being a simple matter of gritty stuff wearing away wood, abrasive science is complex. Many factors affect the performance of sandpaper, including the abrasive material, how uniformly the particles are graded, their shape and how they break down under pressure, the coatings applied to the abrasive surface, and much more.
For our purposes, aluminum oxide abrasive is the go-to material for most hand and power sanding. Aluminum zirconia is a premium material with greater durability for power sanding. Silicon carbide comes in very fine grits useful for smoothing between and after coats of finish.
The "paper" backing ranges in weight from the thinnest, A, used for the finest grits, to F, used for heavy power sanding. Good quality backing paper is fiber reinforced for flexibility and durability. Stearate is added to the surface coating to prevent it from loading with accumulated sanding dust.
Sandpaper grit for most woodworking ranges from very coarse 60 to very fine 400, though there are more extremes available, especially at the finer end. Most sanding materials are now graded by the FEPA system, sometimes designated by the letter "P" before the grit number, which more uniformly grades the particles and has mostly replaced the older CAMI system.
Stearated aluminum oxide 9" x 11" sheets are the mainstay for hand sanding. Keep a supply of grits: 80, 120, 150, 220, 320 and 400. Cheap sandpaper ultimately will waste your time and money. Norton 3X and 3M Sandblaster are excellent and widely available in retail stores. Klingspor's online catalog stocks a phenomenal variety of excellent sanding tools.
When sanding surfaces, use a moderately firm but resilient backing for the sandpaper. The traditional solid cork block, front left in the photo below, is hard to beat for this. Tear the sandpaper sheet across its width into three pieces and wrap one around the block as shown in the photo at top, resetting it later to expose fresh grit. Larger proprietary sanding blocks, such as the one by Norton shown here, make fast work of sanding large flat surfaces.
For sanding curves, I find dedicated shop-made blocks, like the ones at right in the photo above, work best. Shape them as needed and apply thin cork or rubbery material to cushion the sandpaper. Adhesive-backed sandpaper, available in rolls, is especially handy for these.
Use the force
Let's face it, sanding is not a lot of fun so it helps to have electricity on your team. The essential wood sanding power tool is the random orbital sander (ROS). These tools spin a 5" or 6" disc of sandpaper but the spinning axis itself wanders randomly within a small circle, usually about 3/16". This motion efficiently removes wood while minimizing swirl marks.
The larger ROS, at left in the photo, can remove wood more aggressively yet still leave a fine finish, while the smaller, less powerful palm-type ROS, at right, is easier to handle.
Hook-and-loop attachment facilitates switching the sandpaper discs on the base of the ROS. Sanding dust is taken up through holes in the discs, making sanding more efficient, cleaner and healthful. Attaching the hose of an auto-start shop vacuum to the sander will capture almost all of the dust. If you don't have a shop vac, the filter canister that attaches directly to the sander is still far better than nothing.
A gum rubber block is invaluable for quickly cleaning the sanding discs. For sanding work that releases any significant dust into the air, a dust mask with a NIOSH rating of at least N95 (99+ is better) is a must for healthful woodworking.
Whether for smoothing, shaping or removing surface defects, the key to sanding is to start with the correct grit because all subsequent finer grits serve only to successively remove the scratches of the previous grit. Experiment to find an initial grit that will strike a balance in creating a uniform surface reasonably quickly without creating unnecessarily deep scratches that will take too long to remove with successively finer grits.
For surfaces that will receive a film finish such as varnish, shellac, or lacquer, 220 is a good final grit for most woods. An oil finish does not build on the surface so it is better to sand up to 400 grit before applying finish.
Power sanding with the ROS is fast and efficient, so I use it whenever possible, but I always complete the job by hand sanding along the grain with the final grit to remove any swirl marks and leave the best uniform final surface on the wood.
Start with these sanding tools
There is an enormous array of woodworking sanding tools available in addition to those discussed here. Power sanding tools include oscillating spindle/belt sanders, stationary disc/belt sanders, and profile sanders. Hand sanding tools include sanding sponges, shaped backers for curves, and much more.
The basic starting kit I recommend is:
- High quality 9" x 11" aluminum oxide sheets, 80, 120, 150, 220, 320 and 400 grit
- Cork block
- Cork or rubber sheet for making your own curved sanding blocks
- Random orbital sander, large or palm, 5" or 6", depending on the scale of your projects
- High quality hook-and-loop discs, starting at 60 or 80 grit up to at least 220
- Gum rubber cleaning block
- Dust mask rated at least N95