Sanding is a most necessary and skilled aspect of wood working. The trick is to become fast, efficient, and thorough, so that you can do a great job without dreading the sanding process.
Sanding Grit: Not to be confused with Grits, the numbers refer to the size of the rocks they glue on the paper. The higher the number the smaller the rocks they use. The standard grits we use for typical woodworking are 80, 100, 120, 150, 180, and 220. Then, the paper gets very fine and you see 240, 320, 360, 400, 500, 600, and 1000. Some industrial papers go up to 20,000 grit for polishing real fancy stuff. The numbers on the back of the paper can be confusing. Simply remember that when you see random numbers on the back of the paper that are not the set grit numbers, that you are looking at factory product numbers and not grit info.
Grits: Corn meal hot cereal served best with butter—maybe jam also, and then put on plate with eggs, hash browns, bacon, sausage, biscuits, and on a good day steak!
How To: All the machines have 80 grit, so start hand sanding with 100 or 120 grit. Get all defects out with the roughest grit. Progressively use less course paper until you are polishing the wood with the smooth stuff above 220 grit. As you work your way up through the finer grits you simply must sand out the scratches left by one paper with the slightly smaller scratches with the next.
Types of Abrasives:
There are five main types of sandpaper available, but not all are conducive for woodworking. Glasspaper, also known as flint paper, is very lightweight, typically a pale yellow color. Glasspaper disintegrates easily, and is rarely used for woodworking.
Garnet paper is usually a brownish-red color, which is commonly used in woodworking. It will not sand wood as quickly as other sandpapers, but leaves a better finish. Garnet is an excellent choice for finish sanding.
Aluminum Oxide is another common type of sandpaper for woodworking projects. It is the type of paper most often used in power sanders. Aluminum Oxide is more durable than Garnet paper, but doesn’t leave as nice of a finish.
Silicon Carbide paper is typically a dark gray or even black. This type of paper is used primarily for finishing metals or for “wet-sanding”, using water as a lubricant. While some advanced finishes use Silicon Carbide paper, it is not typically used in woodworking.
Finally, Ceramic sandpaper is made of some of the most durable abrasives available, and can remove considerable amounts of material in a hurry. Ceramic paper is often used for belt sander belts, but sometimes is used for hand shaping of wood. It will usually leave a very rough finish, so exercise care when using Ceramic sandpaper, particularly on plywood and veneers, where it can quickly sand through the finish layer and ruin a piece.