4 Stationary Sanders
4.1 Stationary Sanders Overview
Stationary sanders, which can include disc, belt, spindle, drum, and thicknessing sanders, will remove material much faster than sanding by hand. Sanders are used for smoothing surfaces, not removing large amounts of material. A sander is used to finish a surface that a saw or other tool has previously shaped. Choose a stationary sander based on the shape of your workpiece and whether you are sanding an edge, face, or surface of the board.
Discussed in this chapter are two different belt sanders, a disc sander, and a spindle sander. The combination sander has two different stations, a vertical belt sander and a disc sander. Both belt and disc are operated by the same switch. Only one person should use the combination sander at a time. The combination sander is best suited for the ends of boards, while the edge sander is used for straight and convex edges, and the spindle sander for concave edges. Board faces can be sanded with an orbital sander, by hand, or with a drum or thickness sander.
Sandpaper for stationary sanding machines comes in different grits, like sheet paper for hand sanding and abrasives for power hand sanders. However, changing paper on these machines takes more time than a power hand sander. In practice, these machines generally have rougher grits installed (80, 100, or 120), and paper is only changed when it is worn out. Workpieces on stationary sanders are typically not worked through a series of grits like a hand sanding regimen.
The sanding abrasives on these machines can be cleaned with a rubber abrasive cleaning stick. Treat the abrasive cleaning stick like a workpiece; it needs to be held tight against the table and introduced to the abrasive with regard to the direction of travel.
4.2 Stationary Sanders Operation
It is very important to understand the belt, disc, or spindle direction of travel and to feed material against the abrasive action. If workpieces are not held firmly by the operator against a sander’s worktable, they will kickback and become airborne. The sander removes material surprisingly quickly, keep your fingers clear of the abrasive at all times.
These sanders are capable of leaving deep sanding scratches and burns. Introduce material gently into the abrasive, and always finish sand by hand after a machine for the best results. Apply only enough pressure to get the job done. This will ensure you keep surfaces squarer, it is safer, and it will extend the life of the abrasive.
The accuracy of a project can quickly be ruined on a sander. Sanding operations (whether machine, random orbital, or hand sanding) always tend to round edges and surfaces and create pillowed shapes. It is much harder to keep a surface true and flat on the sander than it is on the appropriate saw.
Always take note of the direction the belt or disc is traveling. Keep in mind where a piece will fly if you lose control. Small parts can easily become dangerous airborne projectiles in the shop. If your work piece is oddly shaped, too small, too large/heavy, or difficult to hold in hand securely, consider using a vice and file or hand sand. Hold small pieces with wooden parallel jaw clamps if you must use the sander. This technique is shown on the bandsaw in Figure 3.2.2.
When working on the edge sander, use a light touch. Hold the workpiece firmly and securely. Introduce your workpiece slowly into the belt, using your hands to pin the material down against the worktable. Edge sanders typically have large horsepower motors; they remove material fast and can pull parts from your hands. Edge sanders are for edges only, not ends or faces of boards.
At the vertical belt sander, the belt pulls the material down into the work table. You can move the work piece side to side along the table when sanding and rotate in either direction along a curve (unlike the edge sander).
Always work on the down-stroke side of the disc sander, where the force pulls the workpiece into the table. Because of the rotational movement, the sandpaper is traveling faster at the outer edge of the circle. It’s easy to press too hard, removing too much material or burning the surface.
ALWAYS keep the workpiece under control on the table.
ONLY sand on the down-stroke side of the sanding disk.
DO let the abrasive do the work. DO NOT force workpieces into the belt/disc.
DO tell a monitor or instructor immediately if you notice a hole in the abrasive.
DO wear respiratory protection when working at a stationary sander.
DO use the abrasive cleaner to unclog the paper.
DO NOT leave anything on the worktable.
DO NOT “freehand” above the worktable.
NEVER wear gloves at a stationary sander.
NEVER sand metal on a sander in the wood shop.
4.3 Making A Push Stick: Sanding The Edges
Sand carefully up to your pencil line using the stationary sanders. One of your objectives is learning the machine capabilities, make sure to try each sander. The machines are very different, but there are a lot of crossovers between them.
Focus on removing all bandsawn texture from the edge of the curve. You do not need to sand the straight cuts that form the cleat of the push stick or the interior edges of the holes.
The final step is to break the arrises of the push stick by hand. An arris is the sharp edge from the intersection of two surfaces, in our case, the corners between the shaped edge that was sawn and sanded, and the face of the plywood. The arrises need to be “broken” to prevent splintering. Work with a file or piece of sandpaper by hand to ease them carefully and consistently. Don’t forget the hole’s arrises.
Here are a few tips for working on stationary sanders:
- Always, always, always feather in to prevent flat spots in a curve. Work on increasing longer sections to create the smoothest transitions. The workpiece should always be in motion when in contact with the abrasive.
- Learn to trust your sense of touch, your fingers are more capable of finding small blemishes along a surface than your eyes are.
- Sanders remove high spots. The only way to fair a curve is to remove all the material above the lowest valley. If you saw past the line, sometimes you need to decide between recutting the piece or leaving a saw mark or two rather than significantly changing size and shape at the sander.
