Sand Paper

Posted by Easy WoodCraft on

Feb 6, 2017

No chapter about smoothing tools would be complete without discussing sandpaper. Like many woodworkers, I loathe sanding. It's messy work that I try to keep to a minimum. Whenever possible, I reduce hand- or power-sanding with the appropriate use of planes and scrapers. But unless a project consists mainly of flat, square surfaces (like many Craftsman-style designs), I end up using sandpaper for final smoothing.

Types of sandpaper

There are three main types of sandpaper that are commonly used in a woodshop: silicon-carbide, garnet, and aluminum-oxide (top to bottom in the top photo). For years, all that was available was garnet sandpaper, made from finely crushed semiprecious stones.

This type of paper tends to dull and wear out quickly but has the best reputation for smoothing without leaving scratches. Silicon-carbide paper (often called wet/dry sandpaper) is used primarily for sanding between coats of finish, since it can be used wet. Aluminum-oxide is a relatively new abrasive that stands up well and lasts much longer than garnet.

Regardless of the type of abrasive, all sandpaper is categorized by grits that define the size of the particle (see the chart below).

Although there are many rules of thumb for grit selection, I've found that I usually need only two for smoothing. I start with 150-grit and then finish with 220. This is possible because I don't expect the sandpaper to do what I should have done with a plane or a scraper. Instead of grinding away at an imperfection with a power sander, I'll remove it first with a plane or scraper. Many woodworkers don't realize that it's actually faster this way.

Hand-sanding

If you're planning on sanding by hand, I suggest ripping a standard 9"xll" sheet in half across its width and then folding it in thirds, as shown in the middle drawing on the opposite page. This creates three separate sanding surfaces that can be folded over in turn to produce a fresh surface as the other two sides wear out. Just as important, folding the paper like this prevents the grit side of sandpaper from rubbing against itself which will dull it before you even have a chance to use it.

Sanding block

I also strongly recommend a sanding block, especially if you're working on a flat surface. A sanding block helps to distribute sanding pressure evenly and reduces hand fatigue. Although you can purchase many snazzy sanding blocks with complicated levers and fancy hold-downs, I've always felt a scrap of wood or a cork block wrapped with sandpaper works best. You can quickly change paper and even modify the block to make it better suit the job at hand. As with any sanding, make sure to sand with the grain to prevent cross-grain scratches. Also, clean the sandpaper often by removing it from the sanding block and giving it a sharp rap on the edge of your workbench.

SANDING PLATE

Years ago, the folks at Sandvik came up with a terrific product called a sanding plate that I've grown quite fond of (photo at right). It's basically a serrated metal plate that works sort of like a cheese grater for wood. Precision holes are punched in the hardened steel to create tiny, volcano-like craters with sharp edges (drawing at right).

Since these holes are made with much accuracy the resulting steel plate performs like varying grades of sandpaper, but it doesn't wear out and it rarely, if ever, clogs. The sanding plate is cut into different shapes and sizes and is attached to plastic handles—some in the form of a sanding block, others like files. When the plate finally does wear out, you can strip it off and slap on a replacement plate.

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