The combinations of abrasive, backing, bonding and grit sizes are so great that it would be impossible to cover the subject in a few words. However, general rules are:
With all types, the open, coarser grain is less likely to clog and finer grains produce a finer finish. It is often a good thing to start with a coarse grain and work up to a finer one.
When sanding it is important to sand with the grain and when sanding flat surfaces a cork rubbing block is recommended. Maintain constant pressure and overlap (like lawn mowing) to ensure that all areas are covered.
Clean the paper to reduce clogging.
Store in a warm and dry place. Modern day abrasives tend to fall into two categories.
Coated abrasives in the form of glass or emery paper where the abrasive material is coated or bonded onto a form of paper or cloth backing, and bonded abrasives where the material is bonded together to form a wheel or stone.
Coated abrasives and bonded abrasives are both fields where there are a substantial number of variables. The right selection is essential for best performance.
The need to sharpen tools has been recognised as long as tools have been used. The first method of sharpening was probably through the use of sand stones and then hide such as used in the old leather razor straps.
The medium paper is for hand sanding or for orbital sanders.
The heavy paper open coat will reduce clogging. For machine use and particularly for sanding soft and resinous woods.
Close grain should be used for finishing.
Aluminium oxide cloth backing is for heavier sanding, drum or contour work and for use on metal materials.
This is important. Paper is the traditional material and is still very popular. Laminate and cloth backings are also now used.
Backings are measured by weight of the paper or backing material and are letter coded. 'A' is the lightest at approximately 75 gsm per metre, 'E' being approximately 300 gsm per metre.
The general rule is that the lighter backing is used for finer and more flexible work and the heavier backing for heavier work.
Cloth backings are of pre-stretched material and have been produced for the rough treatment of machines and metal working.
This varies from hide glue to resin. Hide glue being more flexible and suitable therefore for lighter work and resin being more suitable for disc sanders and heavy sanding machinery.
Manufactured from a super abrasive Mono crystalline diamond set two thirds into nickel that bonds them to a perforated precision ground steel base which has been injection moulded onto a polycarbonate/glass fibre substrate. Usually colour coded to denote the grit, they are designed to give an exceptionally sharp edge on most popular woodworking tools including T/C router bits.
This contains natural aluminium oxide crystals and is normally cloth backed and mainly used on finished metals. It can be lubricated with water.
This is a natural material first found in the USA and very effective for finer finishes on all types of timber, including hardwood. It has a form of self-sharpening feature which means that as it wears, it breaks down into new cutting edges. Must be used dry.
Made from crushed glass, it is used for joinery and woodwork and hand sanding. Wears quickly.
All abrasives come in different grit sizes. Grits are sieved for measurement, the grit sizes being governed by the sieve mesh. The larger the size of the grit the coarser the grain and vice versa.
Grit sizes vary between 16 the coarsest, to 400 (the finest for woodwork) and even up to 1,200 for the very fine specialist finishing materials for metal.
These should be a must for virtually every tool user for sharpening chisels and plane irons etc. The most popular selling size is the 8in x 2in combination grit which provides coarse on one side and fine on the other side of the stone. Light oil is applied to the stone prior to sharpening.
This paper has a form of self-lubricating process for fine finishing and is the material normally used on a waterproof backing paper for wet or dry finishing.