This month's topic is sandpaper & abrasives. I've listed out the most common abrasives with definitions and their normal uses. I've used all of them over the years with varying results. They all have their good and bad sides. In my own woodworking I tend to rely on the ALO paper for the majority of work and the SIC wet/dry paper for final finishing. My experiments with the pumice and rottenstone showed me it would take a lot of practice to develop some finesse and achieve good results.

Garnet
A naturally occurring mineral, which up until the last 10 years has been the traditional choice of woodworkers. Not as hard or long lasting as man made abrasives. Relatively sharp, but very weak bonding structure so it wears out quickly. Very inconsistent when compared to synthetics. Used primarily in woodworking as garnet dulls too quickly to be used in metalworking. I find that garnet paper, especially the cheaper brands, leaves fine particles of grit in the wood, which is not always easy to remove afterwards.

ALO
Aluminum oxide. It has pretty much replaced Garnet as the abrasive of choice. Hard grained, long lasting and can be used on wood, ferrous metals, non-ferrous metals and solid surface materials. Finer grits can be used in sharpening applications. A tough, blocky shaped, man-made grain used for high speed grinding and finishing of metals, wood, and other high tensile strength materials without excessive fracturing or shedding. Wherever the ability to resist fracturing is the main consideration, aluminum oxide will outperform all other coated abrasive grains.

Emery

Emery cloth is a strip of fabric with fine metallic or synthetic particles bonded to it. These particles are normally a variety of corundum that contains aluminum oxide set in iron oxide. Wet and dry paper is similar but the backing is a form of paper, which doesn't fall to pieces when wet. Good for rust removal, polishing, deburring and corrosion and paint removal.

SIC waterproof
Silicon carbide. Can be used wet or dry. A very hard, very sharp, man-made abrasive suited for glass, plastic, rubber, ceramics, solid surface materials, and non-ferrous metals and for final wet sanding on wood, creating a high gloss surface. A very friable grain, silicon carbide cuts faster under light pressure than any other grain used in coated abrasives.

Alumina Zirconia
Very hard and sharp grained, which works well on stainless steel, titanium and other hard steels. Can also be used on wood. A very fine, dense, man-made crystalline grain, which can be used for aggressive stock removal. Zirconium is a very dense material with a unique self-sharpening characteristic, which gives it long life on heavy stock removal operations.

Crocus Cloth
This is a very fine grit iron-oxide coated abrasive on a cloth backing. It is used to polish after most of the work has been done with emery or aluminum oxide. Normally used only on metals.

Steel Wool
Steel wool comes in eight grits and is used for everything from removing paint and rust up to fine furniture polishing. The three coarsest grits (No's. 2, 3 & 4) are for removing varnish, paint, rust, etc. The No.1 is can be used for applying wax and polish for hardwood and tile. O Fine - is for cleaning woodwork, painted surfaces and floors. OO Very Fine - is for metal polishing. OOO Extra Fine - is for rubbing down of paints, shellacs and varnishes before final coat. OOOO Finest - is for the final rubbing down of shellacs & varnishes.

Fiber pads
Fiber pads are man made nylon or polyester wool, which is impregnated with grit. They are available in coarse, medium, fine and very fine. A grit free polishing pad is also available.

Abrasive Blocks
Abrasive blocks have an aluminum oxide paper bonded to either a soft foam pad or a stiffer Styrofoam block. They come in many grits and are particularly good for sanding mouldings and curved surfaces.

Closed Coat
Closed coat means the abrasive grains are adjacent to each other with no space between. The majority of applications will benefit from closed coat material because it allows for more material removal.

Cloth Weights JF - Light weight, very flexible J - Light weight, flexible XF - Heavy, flexible X - Heavy, stiff Y - Very heavy, very stiff

Paper Weights A - Very light weight, flexible B - Light weight, flexible C - Medium weight D - Heavy weight, stiff E - Heavy weight, flexible F - Very heavy weight, stiff

Open Coat
Open coat means the grains are set apart from each other, achieving a surface coverage of about 60% or more. In situations where loading is likely (soft, non- ferrous materials, painted surface, wood, etc.) open coat will resist loading and clogging and extend the useful life of the abrasive.

Stearate
An additive, which prevents the abrasive to be loaded up when sanding soft, resinous woods.