Quick answer: This is a plain-English glossary of the terms used in coated abrasives – the words on a belt label, in a machine manual, or in a conversation with a sales rep. It covers grain, backing, bond and coating terms (aluminum oxide, X-weight, size coat, open coat), splice and machine terms (butt joint, contact wheel, platen, tracking), grading terms (grit, CAMI, FEPA) and the defects you're trying to avoid (chatter, loading, glazing, burning). Terms are alphabetical; the most-searched ones are grit, open coat, closed coat, backing weight, splice, loading, SFPM and friable.
Jump to: A · B · C · D · E · F · G · H · I · J · L · M · N · O · P · R · S · T · V · W · Z
A
- Abrasive
- A hard substance used for abrading, grinding, polishing and lapping. Natural abrasives include emery, garnet, flint and crocus; manufactured (electric furnace) abrasives include aluminum oxide, silicon carbide, zirconia alumina and ceramic aluminum oxide. One of the three components of a coated abrasive, with the backing and the adhesive.
- Abrasive machining
- Rough grinding metal parts to size (roughing and shaping) and finishing them to tolerance and surface finish (dimensioning and finishing) with coated abrasive belts.
- Abrasive planing
- Sanding glued-up or lumber-banded panels on a wide belt sander before intermediate sanding or the application of overlays.
- Active filler
- A fine solid material dispersed in the bond adhesive that reacts chemically during grinding to promote a faster or cooler cut. Used mainly for grinding stainless steel, high-nickel alloys and titanium. Also called a grinding aid.
- Adhesive
- The substance that bonds the abrasive grain to the backing. See make coat and size coat.
- Aluminum oxide
- An abrasive grain made by fusing bauxite. Brown, tough and durable; the most widely used coated abrasive mineral.
- Arbor
- The spindle of a grinding machine on which the contact wheel or idler pulley is mounted.
- Arbor hole
- The hole in a contact wheel, idler pulley or disc sized to fit the machine arbor (7/8" on a standard 4-1/2" angle grinder disc).
- Arc of contact
- The portion of the belt's circumference touching the work when running over a contact wheel.
- Automatic tracking
- A light- or air-controlled system that constantly adjusts the belt during operation so it runs true on the contact roll or idler.
B
- Backing
- The flexible or semi-rigid material the grain is bonded to: paper, cloth, fiber, film or combinations.
- Bands (abrasive)
- Cylindrical cloth abrasives, spirally wound on an inner liner, used on expanding rubber drums for sanding corners, grooves and contours.
- Batch system
- In rough lumber sanding, feeding several boards side by side as one unit roughly the width of the belt so they're sanded simultaneously.
- Belt guard
- The protective cover over an abrasive belt, normally part of the machine, that protects operators from injury.
- Belt joint
- The area where the two ends of a belt are spliced together with adhesive. See butt joint and lap joint.
- Belt joint marks
- A pattern left on the workpiece at regular intervals, usually because the joint specification isn't suited to the application.
- Belt tension
- The force applied to a belt in use, normally expressed in pounds per inch of belt width.
- Buffing
- Smoothing and brightening a surface with an abrasive compound pressed against it by a soft wheel or belt.
- Burning the work
- A change in the workpiece from excess heat, seen as discoloration or a burning smell.
- Burnishing
- Using coated abrasives to refine a surface to a smooth, lustrous finish on metal, leather and similar materials.
- Butt joint
- A belt splice where the two ends are butted together with no overlap and held by a strong, thin reinforcing tape on the back. Bi-directional.
C
- CAMI
- Coated Abrasives Manufacturers Institute, the North American body whose grit grading standard uses plain numbers (120, 220).
- Ceramic aluminum oxide
- A micro-crystalline abrasive grain made by a sol-gel process. Two to three times tougher than fused aluminum oxide; fractures to stay sharp.
- Chatter
- An undesirable repeating pattern on the workpiece at regular intervals, usually from an out-of-round or out-of-balance condition on the machine, or from the belt joint.
- Chicken tracks
- Small interrupted indentations or raised areas in a pattern on a flat wood workpiece after sanding, associated with wide belt and oscillating drum sanders.
- Chips
- The pieces of material removed by an individual abrasive grain.
- Closed coat
- A coated abrasive with the coat side completely covered by grain. Maximum cut on hard materials.
- Coated abrasive
- A product made by bonding abrasive grain with an adhesive to a flexible or semi-rigid backing: sandpaper, belts, discs, rolls.
- Compensator
- A wide belt sander option that slows the feed automatically when oversized stock enters the machine, protecting the belt and the machine.
- Contact wheel
- The wheel – rubber, metal or felt – the belt runs over and the work is applied against. Aggressiveness depends on density, serration angle and depth, and the ratio of groove to land width.
- Conventional grinding
- Presenting the workpiece to the belt against the direction the belt is running.
- Cross-scratch
- A scratch made by sanding across (at 90° to) the direction of the wood grain.
D
- Depth of cut
- The amount of stock removed in each pass, usually in thousandths of an inch.
- Disc
- A round, flat coated abrasive, with or without a center hole, attached to a rotating plate or backup pad.
- Drawer sander
- A machine for sanding the dovetails, front and rear, of wooden drawers after assembly.
- Dubbing
- Tapering of the edges of flat stock run through a wide belt or drum sander, usually on the leading or trailing edge.
- Dulling
- Wear of the cutting edges of the grain through use, ending in inefficient cutting. The belt should then be discarded or moved to lighter work regardless of appearance.
E
- Edge cut
- Grooving or rounding of the workpiece edge from excessive stock removal at the belt edge. Also called edge snipe.
- Edge sander
- A machine for sanding edges in a furniture plant.
- End grain
- The cut face of wood that exposes the growth rings – the end of a 2 x 4.
F
- Feed lines
- A pattern on the work produced by grinding; finer finishes show finer, more visible lines. A barber-pole pattern indicates incorrect grinding conditions.
- FEPA
- Federation of European Producers of Abrasives, whose grit grading standard uses the P prefix (P120, P400). Tighter particle-size tolerance than CAMI.
- Fining out
- Generating super-fine finishes in the last stages of polishing, either as the final step or as preparation for buffing.
- Finishing paper
- Products on A-weight (40 lb) backing, normally in fine grits, for hand sanding a final finish.
- Finishing room
- The area of a furniture plant where wash-coat and sealer sanding are done.
- Fish eye
- A spot in a coated surface where the coating is thinner, usually caused by a trace of silicone or similar contaminant. Silicones are rigorously excluded from quality coated abrasives.
- Flap wheel
- Flat pieces of coated abrasive fastened to a core like the spokes of a wheel; the slapping action of the flaps abrades and polishes.
- Flex
- Controlled breaking of the adhesive bond so a coated abrasive can bend. See single, double, full and L flex.
- Flutter sanding
- Sanding irregular carved shapes with eight-wing discs folded into a pinwheel.
- Friable
- Describes a grain that fractures under pressure to expose new sharp edges – self-sharpening. Ceramic and zirconia are friable in a controlled way.
G
- Garnet
- A natural red abrasive grain made by crushing garnet, once widely used on paper and cloth for woodworking.
- Glazing
- Formation of a layer of the ground material over the cutting edges of the grain. Avoided by correct abrasive selection, contact wheel, lubricant or belt speed.
- Glue bond
- Coated abrasives using animal hide glue in both the make and size coats, alone or with an inert filler.
- Grain fracture
- The shape and structure of abrasive grain – blocky, chisel-shaped, wedge and so on.
- Grain size
- The nominal size of the abrasive particle, expressed as a grit number.
- Graphite-coated canvas
- Canvas with a layer of graphite, placed between the platen and the back of the belt to reduce friction on platen-type machines.
- Grinding
- Removing material with a coated abrasive, usually at coarse grits.
- Grinding wheel
- A bonded abrasive: grain and bond formed into a solid wheel.
- Grit
- The designation of grain size, historically the number of openings per linear inch of the screen the grain passes through. Lower numbers are coarser.
H
- Hand block sanding
- Sanding with belts or sheets on a flat or shaped block; flat blocks for flat stock, formed blocks for mouldings.
I
- Idler
- The adjustable machine roller in a belt system that provides tracking and, on some machines, tensioning.
J
- Jitterbug
- A reciprocating or oscillating pad sander with a sheet fixed to a felt or rubber pad, for flat sanding of wood.
L
- Lap joint
- A belt splice made by overlapping the two ends about 3/8" and bonding them. The grain is skived from the bottom lap first. Directional – run with the arrow.
- Load meter
- An optional meter on wide belt sanders reading main-motor load, often as a percentage of rated horsepower.
- Loading
- Filling of the spaces between grains with swarf, reducing stock removal. Reduced by open coat construction or a lubricant.
- Long scratch
- The scratch pattern from stroke or platen sanding, as opposed to the short scratch from a contact wheel.
M
- Machine room
- The area of a furniture plant where rough lumber is dimensioned, glued into panels and machined, often on wide belt abrasive planers.
- Make coat
- The first adhesive layer, applied to the backing to anchor the grain. Also called the maker coat.
- Mould block
- A preshaped backup block behind an abrasive belt that conforms to the moulding being sanded.
- Mould sanding
- Sanding and finishing wood mouldings with a mould block and a very flexible belt.
N
- Natural abrasives
- Abrasives that occur in nature – garnet, flint, crocus and emery – as opposed to electric-furnace abrasives.
- Noseblock
- The fixed, non-turning contact surface on abrasive machinery, common in woodworking plants.
O
- Open coat
- A coated abrasive in which the grain covers about 50 to 70 percent of the coat side, leaving space for swarf. Reduces loading on soft materials.
- Operating speed
- The speed of a coated abrasive in use, in RPM or surface feet per minute.
- Oscillating sander
- A pad sander with a short, high-speed oscillating stroke for fast stock removal.
P
- Pinch rolls
- Opposed rolls, usually rubber, that apply pressure to the workpiece to maintain feed rate and alignment.
- Platen
- A flat or shaped support behind the belt where the work is applied, often faced with resilient material and graphite canvas.
- Pneumatic drum sanding
- Contour sanding with abrasive sleeves on canvas-covered inflatable rubber drums.
- Polishing
- Smoothing roughness or putting a high finish on metal with a coated abrasive polishing belt.
- Portable grinder
- A hand-held coated abrasive machine – a portable disc or belt sander.
- Profile
- The surface configuration of a workpiece – finish, flatness and so on.
- PSA
- Pressure-sensitive adhesive – an adhesive on the back of a disc that allows quick application to and removal from a backup pad. Single use.
R
- Rough grinding
- The first grinding operation, reducing stock rapidly without regard to finish.
- Rough lumber sanding
- The first sanding operation on lumber after sawing.
- Rubbing
- The final phase of finishing, in which the surface is rubbed by hand or machine to the required luster.
S
- Sanding room
- The department of a furniture plant devoted to machine sanding of dimension stock before assembly.
- Satining
- Precision leveling of the coated abrasive surface to prevent scratching of soft material.
- Scalloped edge belts
- Belts with edges slit in a scallop pattern, overhung past the contact wheel edge to grind or polish a fillet.
- Sealer coat
- A finishing coat, generally nitrocellulose, that closes the pores of wood and promotes adhesion of later coats.
- Sealer sanding
- Removing roughness and surface impurities from the sealer coat before the finish coat.
- SFPM
- Surface feet per minute – the linear speed of the belt. SFPM = π × wheel diameter (in) × RPM ÷ 12.
- Shoe
- A platen or smoothing bar – a flat metal support behind the belt, often faced with felt or foam tape.
- Size coat
- The second adhesive layer, applied over the grain to lock it in place. Also called the sizer coat. May carry grinding aids or anti-load additives.
- Smoothing bar
- A platen-type device behind the belt at the point of contact, usually covered with graphite canvas, used on wide belt machines to improve finish.
- Specialties
- Coated abrasive forms other than sheets, rolls, belts and discs – assemblies, flap wheels, cones, bands.
- Spool sanding
- Sanding convex or concave curves on compound shapes such as mirror frames and headboards.
- Straight-line sanding
- A simple reciprocating hand sander, as opposed to one with orbital motion.
- Stroke sander
- A machine with two or more pulleys carrying a long belt over a table; the operator presses a backup block against the back of the moving belt to sand the work.
- Swirl marks
- Grinding marks or scratch patterns left by rotating tools such as orbital sanders.
T
- TJ joint
- Thin joint – a special lap joint construction for applications needing a smooth-running belt with minimum joint thickness.
- Tracking
- Adjusting the idler pulley so the belt runs properly aligned on the contact wheel.
V
- Vonnegut wheel
- A brush-backed wheel carrying coated abrasive strips, used to sand contoured workpieces.
W
- Wash coat
- A very light sprayed coat of finish that adds depth to color after staining; requires light scuffing.
- Wide belts
- Coated abrasive belts 14" wide and wider. Belts over 52" wide are often made with multiple joints and called sectional belts.
Z
- Zirconia alumina
- An alloy abrasive grain of aluminum and zirconium oxides – tough, self-sharpening, blue or green in color, used for coarse stock removal on metal and wood.
Missing a term? Ask us and we'll add it. For deeper reading: sanding belt materials, grit grading, belt joints and belt speeds.
