History

The origin of coated abrasives is lost in antiquity. Their development through the ages is the result of the work and contributions of many people. When and where coated abrasives were invented, and when they were first introduced into this country, cannot be answered authoritatively. Coated abrasives have evolved from technological developments to which many people have contributed, rather than from a single invention. As a background for the lessons to follow, a short outline of their development may be helpful.

Dried fish skins were used at an early date for smoothing and polishing wood. This was improved by the development of "shagreen", a material originally made from the skin of certain species of rough scaled sharks. Later, shagreen was made from other types of skins into which a granular material, such as seeds, had been worked to produce the characteristic roughness. It was used both as an abrasive and as an ornamental material depending on the texture. It was in common use in the 16th century as shown by the introduction into the English language of the word "shagreen" at that time. This was an anglicized version of the French word "chagrin", meaning to vex or annoy.

Abrasive paper was sold in the streets of Paris in 1769 as illustrated by an old print of that date; but it is not known how it was made. The first known article describing a method of making coated abrasives was published in 1808. Calcined and ground pumice was mixed with varnish and spread on paper with a brush.

Emery cloth was invented in England in 1831 by Lothrop. He used sand, powdered glass or emery mixed with glue. This mixture was spread on cotton cloth.

A man named Fisher was granted a United States patent in 1835, for a machine and a method for making coated abrasives. Steam was allowed to act on the uncoated side of the paper to prevent curling. The sand was sprinkled from a sieve onto glue coated paper carried by an endless belt. In 1844, Fremy in France, began the commercial manufacture of glass and emery paper with a machine of somewhat different design than the one for which he obtained a patent. In 1856, emery paper of graded degrees of fineness was manufactured in England. Powdered emery was blown into a chamber in which glue coated sheets of paper were hung at various heights. The highest paper received the finest dust, while the lower sheets received the coarser dust. In 1861 a German patent was granted on a flint abrasive paper.

In recent years development work has been done in many countries, and vast improvements have been introduced until coated abrasives have become known as the "Modern Tool of Industry".

In the manufacture of commercial abrasive products, seven distinctly different abrasive materials are employed. In order of their respective hardness (soft to hard) these are: crocus, flint, garnet, emery, zirconia alumina, ceramic, aluminum oxide, silicon carbide and diamonds. The majority of modern coated abrasives have working surfaces of man-made abrasive minerals which are harder, tougher, and sharper than anything nature has to offer except for the diamond.

The bonding materials holding the minerals to the flexible backings, and the backings themselves, have been specifically developed to meet the rigorous demands on these modern tools. The manufacturing controls of coated abrasives are now so great that the consistency of any one product is almost invariably better than that of the material on which it is being used.

Coated abrasive products are employed in the manufacture of almost every product used, whether in the factory, the office, the home or on the farm. They are used on products on the land, in the air and on the sea. Even in the rare cases when coated abrasive products were not used directly to make a product. The machines that made the product were themselves usually brought to accurate and polished perfection with the aid of coated abrasives in one form or another.

The coated abrasive industry is very competitive and has become highly technical. During the third quarter of this century, and more particularly over the last 10 years, the coated abrasive industry substantially expanded the use of its products by developing many new and improved items as well as many new end uses for them. There are probably some 40,000 different specifications of these products made and sold by the industry today, as compared to but a few thousand at the beginning of this expansion.

What Raw Materials are Used in the Manufacture of Coated Abrasives‌

The coated abrasive industry uses approximately, 750 different types of raw materials. The major classifications are - cloth, paper, vulcanized fiber and combinations of these laminated together, as well as the various types of abrasive grains for the abrading media and resins, varnishes, glues and fillers for the adhesive or bonding systems. Many of these materials have been developed solely to meet the requirements of the coated abrasive industry. For example, the backings and bonds used on coated abrasive products today provide flexibility with strength, resistance to stretch, insulation from heat, and overall uniformity unobtainable in such products until the coated abrasive industry created the demand.

Abrasives

Silicon Carbide – The hardest and sharpest manufactured abrasive and bluish black in appearance. Its hardenss and sharpness make it ideal for sanding, polishing and finishing non-ferrous metals (aluminum, bronze, brass, magnesium, titanium, etc.), glass, plastics, rubber, fibrous woods, and other low tensile or soft materials. Recent product developments include utilizing silicon carbide grain with chemically active bonds for special metal applications.

Aluminum Oxide – A tough durable manufactured abrasive characterized by long life of its cutting edges and points and perhaps the most widely used of the man-made minerals. It ranges from white to dark brown depending on the titanium content and can be toughened or alloyed with other minerals depending on the need. It is well suited to high tensile materials and is used over a broad range of ferrous and non-ferrous metals, and both soft and hard woods.

Zirconia Alumina – A high performance alloyed abrasive formed by zirconia deposited in an alumina matrix. Excellent for heavy duty stock removal requirements for virtually all type of metals as well as some woods

Ceramic Alumina – A new, high performance alumina base abrasive. This man-made mineral is a chemical rather than a fused material. The excellent structure created by the chemical manufacturing process and the addition of magnesia provides for controlled fracturing and thus the continuous renewal of sharp cutting edges. The abrasive is well suited to a broad range of medium to heavy stock removal jobs on steel, cast iron, aluminum, forgings, fabrications, etc.

Garnet – A natural abrasive. In appearance, it is reddish brown. By special heat treat­ment a tougher, sturdier grain is produced for use on coated abrasives. It is used almost exclusively in wood sanding.

Flint – A natural abrasive, grayish white in appearance. Quite sharp, the abrasive lacks toughness and therefore, is generally limited to use in sheet form for home repair, etc.

Emery – A natural abrasive that is dark gray in appearance. It is used rather extensively for light polishing of metal surfaces where its blocky shape enhances finishing action,

Backings

Paper - the paper employed by Carborundum Abrasives Company is made with the strongest and toughest fiber stock available. It is available in several different weights, thicknesses and widths according to the application for which it is intended. Two specific types of paper are used - Fourdrinier and Cylinder. The particular characteristic of Fourdrinier Paper is that it is a balanced sheet having a high resistance to tearing and is very flexible. It is made in a single layer which can be obtained in several different weights. Cylinder Paper is made of several plies with the fibers distributed to provide maximum strength in the lengthwise direction. This feature makes it especially adaptable for use in the form of belts and drum covers.

Both types of paper come in large rolls, in the following weights:

A weight, Fourdrinier only -40 lbs. per ream*

C weight, Fourdrinier only - 70 lbs. per ream"

D weight, Fourdrinier only - 90 lbs. per ream'

E weight, Fourdrinier and Cylinder - 130 lbs. per ream*

F weight, Cylinder only - 170 lbs. per ream*

(*A paper maker's ream is 480 sheets 24" x 36", not 9" x 11".)

Prior to coating of each roll, the roll is carefully check­ed by experienced technical personnel to maintain rigid standards,

Cloth – Several different types and weights are used by Carborundum Abrasives Company in the manufacture of cloth backed abrasives. These ranges from soft flexible jeans to the very heavy duty sateens and knits. Some coated abrasive manufacturers will use a variety of backing material including heavy duty ducks and light weight twills. All cloth backings manufactured by Carborundum Abrasives Company are engineered to established technical specifications under rigid quality control.

J - is commonly used to designate a light weight twill weave cloth. It is most frequently used in applications where flexibility of the abrasive product is required to conform to shapes and contours in the workpiece. Flexbac Metal Cloth, Flexbac Resin Cloth, Moulding Cloth and light duty Resin Cloths are some of the major users of jeans.

X - is commonly used to designate a medium to heavy duty backing which can range from medium /heavy twills (drills) to specially designed sateens for tougher applications. High strength and low stretch are the key elements while major requirements can range from general purpose non-waterproof to the most heavy duty wet or dry application, depending on the commodity.

Y - is commonly used to designate a very high strength low stretch heavy duty twills, sateen or knit backed product. Specific applications would include heavy duty stock removal requirements in metal working and wood planing industries.

S - is commonly used to designate a special sateen weave engineered to be used exclusively for sectional belts.

Fibre - vulcanized fibre backing made of several layers of impregnated paper resulting in a very hard and strong material. This backing is primarily used on resin bonded fibre discs for portable disc grinder applications.

Combination - backing is made by combining strong paper stock and light weight cloth with adhesive; is used where resistance to tearing and breaking is a requirement. It is more commonly used in floor refinishing applications.

Adhesives

Glue - The glues employed in coated abrasives are specially made animal hide glues with great strength and flexibility. They are used dry, on less severe mechanized operations, and for hand sanding.

Calcium Carbonate Filler - When mixed with glue, tends to provide denser and more heat-resistant bonds, lending the product for uses on tougher work. This type of adhesive is used on most dry mechanized operations.

Resin - the resins are either urea or phenolic resins with the latter most widely used. Phenolic resins are hard, tough and heat-resistant adhesives and well suited to the most demanding coated abrasive applications. Because they can be manufactured to fit virtually any applications, resin bond products are the most widely used coated abrasives. The addition of fillers further influences strength and heat dissipation. Resins will continue to evolve into new forms as the market demands.

Finishing Coated abrasive products are coated in widths from 36 inches to 68 inches depending on the end uses for which they are intended. They are dried or cured, or both, and conditioned to the proper moisture content for future processing into the form required by the various consumers. They are then wound into rolls which vary in length from 200 yards to approximately 2,000 yards. These are called 'Jumbo Rolls". The average diameter is 36 inches. The rolls are stored in controlled-temperature storage rooms until they are transferred to the finishing plant. The method of processing Jumbo Rolls of coated abrasive products for consumer use in belts, sheets, discs, etc., is known as "finishing" The finishing methods used to convert Jumbo Rolls of coated abrasives include flexing, splicing, slitting into roll form, automatic sheet cutting, disc die cutting.

Flexing and splicing are important components of the product characteristics. Both finished product and variation results in different are discussed in depth in the following two lessons.

 

Processes of Coating

There are two methods employed by the coated industry to coat the backing with grain: Gravity and Electrocoating.

Gravity - The grain is dropped from a hopper onto the adhesive covered sheet (See Sketch 1 opposite). Only a small number of products are gravity coated.

Electrocoating - This process is used in applying the grains or grits to the backing so that each particle literally takes an upright position. In this process the grains are passed into an electrostatic field where they become charged, one end of each grain becoming positive and the other negative

Adhesives

A negative electrode or pole, used in creating the electrostatic field attracts the positive end of the grain particle and repels the negative end. Thus the grain is turned and applied in an upright position on the backing. The result is a sanding or abrading surface that possesses a much higher percentage of keen, upright points. Furthermore, the dispersion of the grain particles is exceptionally uniform. Grinding, polishing and sanding efficiency with electrocoated products is 20-25% better than with gravity coated material.

Coatings

Closed - A closed coating completely covers the surface of the backing. It is employed on most products and is good for severe operations where a high rate of stock removal and a heavy working pressure is required.

Open - A coated abrasive product is called open coated when the amount of grain is reduced to approximately 60% of that of a closed coat. As open coated abrasives load less readily, they are effective on operations where the sanded material tends to clog the coating. For example; solder, soft aluminum, paint, varnish and woodworking.

Inspection

All coated abrasive products are thoroughly inspected in every step of the manufacturing process, and before shipment. Specially trained personnel assure strict conformance to specifications.

Identification

For easier, quicker identification of each coated abrasive product, every item in the line displays the trademark "Carborundum Abrasives". This trademark is applied to the backing of every product.

In addition, it is prominently displayed at the top of each label. The trademark is expressed by the words "Carborundum Abrasives" displayed in bold letters, and this trademark signifies any and all products manufactured by Carborundum Abrasives Company.

Sequence of markings -Other markings of importance in the specification and ordering of coated abrasive products are: quantity, dimension, grit, backing, type of abrasive, type of coating, and flex. Therefore, in identifying the products on both the backing material and the labels, the Carborundum Abrasives Company features:

A. The trademark

B. The product name

C. The grit size

D. The backing

E. The abrasive

F. Coating (if applicable) i.e. open coat

G. Flex

When ordering coated abrasive products these specifications must be listed in addition to the more promi­nent identification markings, thus assuring delivery of the correct product.

The Way to Identify and Specify Coated Abrasives

Using the Carborundum Abrasives Control Key system you can identify the coated abrasives available that meet your job requirements. It classifies all coated abrasives according to one easy-to-understand grading system. It identifies grain, backing and bond (resin or glue) and allows ranking of product from general purpose to premium performance. Product names and markings give essential job information. Uniform, simply defined number and letter symbols make it easy to compare any Carborundum coated abrasive with any other. Every Carborundum coated abrasive has its exact place on the single Control Key Scale.