There are two ways to process wood, cutting or grinding. Although it requires more patience and practice to master cutting techniques (using saws, chisels, planes, scrapers, radial planers, etc.) than mastering grinding techniques, cutting is easier to control and the effect is better. Relatively speaking, I rarely do sanding, and even when I do it, I mostly use hand tools-I don't mind the noise and dust generated by the sander.

Personal preference aside, I have to admit that sanders are useful. Through them, we can make the surface smoother, make the curve smoother, create shapes and rounded corners, or polish the wood to prepare for painting, and so on.

Sandpaper is polished by friction and will leave scratches at the same time. Generally, the finer the sandpaper, the finer the scratches. The finer the scratches, the more obvious the texture of the processed wood.

When sanding the tabletop with 150-mesh sandpaper, I will grind it until the entire surface shows a uniform degree of friction. It is necessary to smooth out all cracks, nicks or scratches that are deeper than the marks made by sandpaper. Then I used 220 grit sandpaper to grind the entire surface, so that I can remove the scratches left by the 150 grit sandpaper. If I continue to use sandpaper with a larger mesh and keep grinding like this, I will end up with a polished surface with only traces of the wood itself.

The sander can be distinguished by its own operating mode: drive a belt to do continuous cycle operation (belt machine), drive a disc (disc sander) with a rotating shaft, rotate a cylindrical sand surface (drum) Sanding machine), driving a piece of sandpaper to move in a track (orbital sanding machine), etc. A brief introduction to these sanders is as follows.

Ordinary electric sander (clockwise from the top left)
Ordinary electric sander (clockwise from the top left): 4 in (10.16 cm) sander, palm sand, belt sander and round sand

One, belt machine

The hand-held belt machine uses continuous and replaceable belts. Normally, the sand width is 3 in (7.62 cm) or 4 in (10.16 cm), and the circumference is 20 in (50.8 cm) or 24 in (60.96cm). The belt machine is mainly used to do large-area grinding work (such as the grinding of the table top). They can quickly grind off the wood on the surface, so they are also difficult to control, prone to pits or bumps.

The belt of the table type belt machine is relatively large, and it is usually used to grind small flat surfaces, or to grind convex surfaces or curves to round and smooth.

The vibrating belt machine has a large belt with a width of 6 in (15.24cm) and a circumference of 25 ft (762 cm). The disc presses the rotating abrasive belt against the wooden board from the inner side of the abrasive belt for sanding. The vibrating belt machine is used in the factory to sand some large and flat surfaces.

The "time saver" is a table type belt machine with a working principle similar to planing, except that it uses one, two or three belts instead of a single cutting head for planing. The belt is installed around the table. The roller makes a cyclic movement, and the size of the sandpaper on each belt will become thinner in turn. At first, the time saver was only found in some large-volume wood workshops. Now that there are smaller and relatively inexpensive time savers, their use is becoming wider and wider.

2. Disc sanding machine

Hand-held disc sander is also called sander. The diameter of the sand disc used is usually 4 in (10.16 cm) ~ 9 in (22.86 cm). The sander is mainly a metal processing tool, but it can quickly grind away a large amount of wood, so it is also very effective for shaping wood. The rotating movement of the sander makes it impossible to sand along the texture-it always leaves scratches transverse to the texture.

For table-type disc sanders, the diameter of the sanding disc is usually 6 in (15.24 cm) ~ 20 in (50.8 cm), and the specific size should match the corresponding table. It is suitable for flattening small wooden boards and the ends of joints, making and polishing convex surfaces, and processing some metal objects. When using, you should place the board on the downward movement of the sanding disc for grinding, and the upward movement will throw the board towards your face.

Three, sand drum machine

The bench sand drum machine performs grinding by rotating a vertical or horizontal cylindrical "drum" (equipped with a cylindrical sand sleeve). The diameter and length of the drum vary. various kinds. Some are solid rubber drums, and some are air in the middle. The sand blasting machine can be used to shape and polish concave and convex surfaces, as well as to process rounded corners and rounded edges.

Four, orbital sanding machine

Orbital sander is also called palm sand. Palm sand is the most gentle sanding machine, mainly used to polish flat and curved surfaces more smoothly. It is a good assistant for woodworkers when processing furniture details. This small sanding machine only needs 1/4 sheet of sandpaper. When in use, press it against the surface of the wood and rub the wood along the direction of the grain. It will shake and form small spiral wear marks, thereby grinding away the excess wood very finely. In the case of high sandpaper mesh, the spiral wear marks caused by palm sand are almost invisible on the wood.

The semi-orbital sander is the larger type of palm sand. It is more useful for surface polishing, but it is less useful in surface polishing.

5. Irregular orbital sanding machine

In the woodworking room, for most surface treatment work, the irregular track sander (round sand) is the best choice. It combines the rotary grinding method of a disc sander and the swirling grinding method of an orbital sander. This makes it very powerful, it will only leave a few scratches transverse to the texture in the passing place.