Abrasives Dictionary

Abrasives Dictionary


Abrasive: A substance used for abrading, grinding, polishing and lapping, such as the natural materials emery, garnet, flint and crocus, and the manufactured or electric furnace materials aluminum oxide, silicon carbide and zirconia alumina. One of the three essential components of a coated abrasive product (backing, adhesive, abrasive grain). 

Abrasives machining: Rough grinding metal parts to a desired size (roughing and shaping) and finishing them to required tolerance and surface finish (dimensioning and finishing) using coated abrasive belts.

Abrasive planing: Sanding of glued-up or lumber banded man-made board panels prior to intermediate sanding or the application of overlays. 

Active filler: A fine, solid material dispersed in the grain bond adhesive of a coated abrasive, which is chemically reactive during grinding to promote faster and/or smoother cutting action by the coated abrasive product. These materials are useful primarily in grinding stainless steels, other high nickel alloys and titanium.

Adhesive: The substance used to bond the grain in the backing on a coated abrasive product.

Aluminum oxide: An abrasive made by fusing the mineral bauxite. 

Arbor: The spindle of the grinding machine on which the contact wheel or idler pulley is mounted.

Arbor hole: The hole in the contact wheel or idler pulley sized to fit the machine arbor.

Arc of contact: That portion of the circumference of the coated abrasive belt touching the work being ground, when on a contact wheel. 

Automatic tracking:  A system that ensures the coated abrasive belt runs true on a contact roll or idler. These automatic tracking systems are usually light or air controlled and and constantly adjusts belts during operation to achieve ideal and consistent tracking.

Backing: A flexible or semirigid material to which abrasive grain is bonded by an adhesive. Paper, cloth, fiber and combinations are the major backings used for coated abrasives. 

Bands (abrasives): Spirally wound and bonded to an inner liner, these cylindrically shaped cloth specialties are used on expanding rubber drums for sanding and polishing hard-to-get-at corners, grooves and contoured surfaces. 

Batch system: In rough lumber sanding, several boards of equal or unequal widths of the same relative thickness are accumulated side by side into a unit roughly equal to the width of the abrasive belt in use. This "batch" is then fed into the sander and all the boards are sanded simultaneously. 

Belt guard:  a protective device covering the abrasive belt, which is normally an integral part of the grinding machine used to protect operators and bystanders from personal injury. 

Belt joint: The area of an abrasive belt where the two ends are spliced together with an adhesive. (See Butt joint and Lap joint). 

Belt joint marks: A pattern left on the workpiece at regular intervals, normally caused by a belt joint specification that is not suitable for the application. 

Belt tension:  The force or strain put on a coated abrasive belt during use, normally expressed in pounds per inch or belt width. 

Buffing: The smoothing and brightening of a surface utilizing an abrasive compound pressed against it by a soft wheel or belt.

Burning the work: A change in the characteristics of the workpiece being ground. Normally detected by a surface discoloration or distinct "burning" odor. 

Burnishing: Using coated abrasives to create a special effect on a workpiece (refining the surface). Usually done to develop a smooth, lustrous surface finish on metal, leather, etc. 

Butt joint (belt): Two pieces of coated abrasive "butted" together (with no overlap) to form an endless belt. A very strong, thin, reinforcing patch is used on the back of the butt joint to hold it together. 

Cabinet room (furniture): The assembly area in a furniture plant where case goods are sanded in-the-white, prior to staining and final inspection.

Chatter: An undesirable, repetitive pattern created on the surface of a workpiece, usually at regularly spaced intervals, due to an out-of-round or out-of-balance condition in the abrasive machine. 

"Chicken" tracks: Small, interrupted indentations or raised areas, appearing as a pattern, on a flat wood workpiece after sanding. Normally associated with wide-belt or oscillating drum sander applications.

Chips: Pieces of material removed by an individual abrasive grain during an abrasive grinding operation. 

Chuck: A device for holding a workpiece being grounded.

Closed coat:  A coated abrasive product completely covered by abrasive grain on the coat side. 

Coated abrasives: Products formed by bonding abrasive grain with an adhesive to a flexible or semirigid backing. 

Compensator: An equipment option on wide-belt sanders that reduces the feed speed of the work transport system when excessively oversized work enters the machine. This feature improves coated abrasive belt life and reduces machine wear.

Contact wheel: The wheel, usually rubber, metal or felt, over which a coated abrasive belt runs and against which work is applied. Aggressiveness varies with density, angle and depth of separation, (if any) and ratio of groove width to land width. 

Conventional grinding: The workpiece is presented to the abrasive belt opposite the direction the belt is running. 

Cross-scratch: Refers to a scratch created by sanding across or 90 degrees to the direction of the wood grain. 

Depth of cut: Refers to the amount of stock removed during each pass of a sanding or grinding operation. Usually expressed in thousandths of an inch, e.g., depth of cut .125 of an inch.

Disc: A round, flat coated abrasive product with or without a center clamping hole that is affixed to a rotating plate or backup pad for portable or stationary grinding. Discs with other-than-round outer peripheries are also manufactured for special applications.

Drawer sander: A special machine for sanding the dovetails, front and rear, or wooden drawers after assembly. 

Dubbing: The tapering of any of the edges of flat stock which has been processed through a wide-belt or drum sander. Most commonly occurs on the leading or trailing edge of the work.

Dulling:  The wearing away of the cutting edges of abrasive grains through use. It occurs to some degree during any abrasive operation and will finally result in inefficient cutting or abrading, at which time the coated abrasive should be discarded or shifted to lighter work, regardless of its appearance. 

Edge cut: Grooving or rounding of the edges of work caused by excessive stock removal at the coated abrasive belt edge. Also called edge snipe. 

Edge sander: A machine used for edge sanding in a furniture plant. 

Edge sheet: A term used to describe a condition in which the abrasive product (usually a belt) during use. Usually caused by too severe an application of the coated abrasive product. 

End grain: That portion of a cut piece of wood which exposes the growth rings of a tree. An example is the end of a 2 x 4. 

Feed lines: A pattern on the work produced by grinding. The finer the finish, the finer and more evident are these lines, due to surface reflectivity. Some types of feed lines (barber pole) indicate incorrect grinding conditions. 

Fining out: Generating super fine finishes on a workpiece during the last stages of a coated abrasive polishing operation. Either the last step in polishing, or as preparation for subsequent buffing. 

Finishing paper: Products manufactured on A-weight (40-pound)
 backings, normally in fine grits, usually used to hand-sand for final finish on wood, metal, etc. 

Finishing room: Refers to the area in a furniture plant where the primary sanding operations for finishing furniture are performed, including wash cut sanding and sealer sanding. 

Fish eye: A spot in a finished coated surface, where the coating is sufficiently thinner than in surrounding areas to cause a visible blemish. This defect is usually caused by the presence on the surface, before coating, of a minute trace of some chemical which prevents easy wetting of the surface by the coating materials. Silicones are one of the most common classes of chemicals of this type, and, as a consequence, they are rigorously excluded from high-quality coated abrasives.

Flap wheel: Flat pieces of coated abrasives sheets (flats) arranged and fastened together on a core like spokes of a wheel. The rotation slapping action of the flap does the abrading and polishing. 

Flex: A controlled breaking of the adhesive bond that holds the abrasive grain to the backing of a coated abrasive product. 

Flutter sanding: Sanding irregular, intricate shapes or carvings which may be found on furniture frames, legs, chair backs, etc. Normally done with eight winged DeLappe Discs folded into a pinwheel configuration.

Garnet: A coated abrasive grain , red in color, made by crushing semiprecious garnet material. Coated on both cloth and paper backings. Garnet is widely used in the woodworking and furniture manufacturing industry. 

Glazing: Formation of a layer of the material being ground over the cutting edges of abrasive grains. It can be avoided by proper selection of abrasive, contact wheels, use of fluid or greases, or changing belt speeds. 

Glue bond: Coated abrasive products that use animal hide glue in both the maker and sizer adhesive coats. The glue may be used alone or with an inert filler or extender. 

Grain fracture: Refers to the shape and structure characteristics of abrasive grain used for coated abrasive products, e.g. blocky, chisel-shaped, strong wedges, etc.

Grain size: The normal size of the abrasive particle expressed in grit number, e.g. grit 50. 

Graphite coated canvas:  Canvas with a layer of graphite adhered to it. Designed to reduce friction on a platen-type grinding machine, it is used between the platen and the back of the belt. 

Grinding: Removing material with a coated abrasive product, usually referring to the use of coarser grit sizes.

Grinding wheel:  A cutting tool of circular shape made of abrasive grits bonded together. 

Grit: Designation of abrasive grain size, reflecting the number of the smallest openings per linear inch through which the grain will pass. 

Hand block sanding: Using a flat block or formed block when sanding with belts or sheets, usually to finish wood workpieces. Flat hand blocks are used to polish flat stock, while formed blocks are used to sand shaped mouldings.

Idler: A machine part in a belt system (may be adjustable) which provides belt tracking and, in some installations, belt tensioning adjustments. 

Jitterbug: A reciprocating or oscillating sander that uses a coated abrasive sheet affixed to a felt or rubber backup for flat sanding of wood. 

Lap joint: Coated abrasive belt joints formed by overlapping the two ends of the abrasive material about 3/8 inch and bonding. The abrasive grain must always be removed (skived) from the bottom lap prior to joining.

Loading:  Filling of the spaces between abrasive grains on a coated product with grinding swarf, resulting in a decrease in stock removal and rate of cut. Loading can be reduced in many operations by using an open coat product construction or lubricant.

Load meter: An optional feature on wide-belt sanding equipment. A meter that reads out the main motor load during operation. Some meters are calibrated in percent of rated horsepower. 

Long scratch: Scratch pattern (long scratches) exhibited on a workpiece after stroke sanding or flat platen-type sanding vs. short "scratch" from a contact wheel or roll operation. 

Machine room:  The area of a furniture plant where the rough cut lumber is dimensioned, glued into panels and machined. The dimensioning portion of this operation is frequently carried out on wide-belt abrasive planers.

Mould block: A preshaped backup block that is positioned in back of an abrasive belt that will conform to the moulding being processed or finished. Blocks can either be held by hand and guided over over the straight line moulding, or held in a stationary fixture and the operator or sander pushes the moulded stock against it. In all cases, the coated abrasive belt is held between the sanding block and the work.

Mould sanding:  Sanding and finishing of woof mouldings using a mould block and very flexible coated abrasive belt.

Natural abrasives: Used to differentiate abrasives that occur in nature as opposed to electric furnace-type abrasives are garnet, flint, crocus and emery. 

Noseblock: Refers to the non-turning, fixed surface contact point on abrasive machinery normally found in woodworking plants.

Open coat: A coated abrasive product in which the grain covers approximately 50 to 70 percent of the coat side surface.

Operating speed: The speed of a coated abrasive product in use, usually expressed in either revolutions per minute or surface feet per minute.

Oscillating sander:  A pad-type sander with a coated abrasive sheet fastened thereon, which uses a short, high-speed oscillating stroke, producing fast stock removal.

Pinch rolls: A set of series of opposed rolls (usually rubber), which apply pressure to the workpiece to maintain proper feed rate and workpiece alignment during the abrasive grinding operation.

Platen: A flat or shaped support which backs up a coated abrasive belt in the area where the workpiece is applied. Usually metal or wood, the platen may be surfaced with resilient material and a lubricant such as graphite-covered canvas.

Pneumatic drum sanding: Contour sanding of chair stock and related parts with coated abrasive sleeves mounted on canvas-covered inflatable rubber drums. 

Polishing: The act of smoothing off the roughness or putting a high finish on metal by using a coated abrasives polishing belt.

Portable grinder:  A coated abrasive sanding machine that is used manually and can be easily transported, e.g., portable disc and belt sanders.

Profile: Refers to the surface configuration of a workpiece, namely, details of grinding surface, finish, flatness. etc.

PSA (Pressure-Sensitive Adhesive): An adhesive applied to the backing of coated abrasive products which permits easy production application and removal to and from a backup pad.

Rough grinding: The first grinding operation for reducing stock rapidly without regard for the quality of the finish.

Rough lumber sanding: Refers to the first sanding operation on lumber, after the sawing operation.

Rubbing: The final phase of finishing in which the part surface is "rubbed" by machine or hand to give the required luster.

Sanding room: Designates a department in a furniture plant that is devoted primarily to machine sanding of dimension stock prior to assembly. 

Satining: A precision leveling of the coated abrasive surface to ensure against scratching of soft material.

Scalloped edge belts: Belts with edges slit in the pattern of a scallop. Used to overhang the edge of a contact wheel to grind or polish a fillet in a workpiece.

Sealer coat:  A coat of finishing material (generally nitrocellulose in nature) designed to close the pores on wood and promote adhesion of subsequent finishing materials.

Sealer sanding: Removing the roughness or surface impurities from the sealer coat surface prior to the finish lacquer coat.

SFPM: Surface feet per minute.

Shoe: Technically referred to as a platen or smoothing bar. A flat metal support located behind the coated abrasive belt. Frequently faced with felt or vinyl foam tape to provide resiliency.

Smoothing bar: A platen-type device backing up the coated abrasive belt at tge point of contact with the workpiece. Usually covered with graphite canvas to reduce frictional heat. Used on wide-belt machines in woodworking, particleboard and plywood sanding to promote better finishes.

Specialties: Coated abrasive forms other than sheets, rolls, belts and discs, e.g., assemblies, flap wheels, cones, etc.

Spool sanding: Sanding convex or concave profile on curves such as mirror frames, headboards and other compound shapes. 

Straight line sanding: Refers to a simple reciprocating-type hand sander as opposed to a sander employing orbital motion.

Stroke sander: A machine that makes sanding contact by "stroking" the back of a moving coated abrasive belt with a backup block or pad. Essentially, these machines consist of two or more pulleys over which the coated abrasive belt travels, a table which supports the workpiece, and means for applying pressure and movement along the belt.

Swirl marks: Grinding marks or scratch patterns left by rotational-type tools.

TJ joint: Thin joint -- Special coated abrasive belt lap joint construction for use in applications where a smooth-running product with minimum joint thickness is a necessity.

Tracking: The act of adjusting the idler pulley in a coated abrasive belt system so that the belt is properly aligned on the contact wheel.

Vonnegut wheel:  Brush-backed wheel containing a loading of coated abrasive strips, used to sand contoured workpieces.

Wash coat: A very light coat of finishing material primarily adding depth to the color of furniture after staining. The solution is sprayed on and requires light scuffing.

Wide belts: Coated abrasive product made in belt form with widths 14 inches and larger (belts over 52 inches wide must frequently be supplies with multijoints and are often called "sectional belts").



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