Reference

Slitting Glossary

The terms a slitting crew, setup operator, or buyer runs into on the line and on a setup sheet, each defined in plain language. Covers the machine, the tooling on the arbor, the parts of the line, and the common edge defects.

46 terms, alphabetical.

Arbor
The rotating shaft in the slitter head that carries the knives and spacers. Its diameter sets the stiffness of the whole build and fixes the bore of every knife and spacer you own. Also called a slitter shaft. Slitter shafts and arbors guide.
Back gauge
A reference stop or setting that positions material to a repeatable point. On slitting setups the term is used loosely for the datum a crew measures strip position and edge trim against when squaring up a job.
Bottom knife
The lower rotary knife in a slitting pair, carried on the bottom arbor. It works with the top knife, offset by a set clearance and overlap, to shear the strip. Its outside diameter is usually larger than the top knife.
Burr
A raised, rough edge left on a strip when the slit does not fracture cleanly. Excess horizontal clearance, dull knives, or worn tooling are common causes. Burr height is a primary measure of slit edge quality. Fixing burr in the slitting problems guide.
Camber
A sideways curve in a slit strip, so it bows left or right instead of running straight. Uneven knife clearance, residual stress in the coil, or mismatched tooling on the arbor can cause it. Fixing camber in the slitting problems guide.
Clearance
The horizontal gap between the upper and lower knife faces, set as a percentage of material thickness per side. Vertical clearance, or overlap, is how far the knives pass each other. Together they control edge quality. Knife clearance reference.
Coil
A continuous length of metal strip wound into a roll for handling and processing. The slitting line pays a master coil off the uncoiler and rewinds the finished narrower strips into smaller coils on the recoiler.
Crossbow
A curl across the width of a strip, so it dishes from edge to edge rather than lying flat. It usually traces to coil set or uneven tension, and shows up when strips are cut to length or laid flat.
Cut to length line
A processing line that cuts a coil across its width into flat sheets or blanks of a set length. Unlike slitting, which cuts lengthwise into narrower coils, it changes length rather than width and produces sheets.
Edge trim
The narrow scrap strips taken off both outer edges of a master coil to remove the rough mill edge and square the material before the working cuts. Edge trim is wound onto a scrap winder or chopped.
Edge wave
A rippled, wavy strip edge caused by the metal being stretched more along the edge than the center. Excess knife overlap, tension problems, or coil shape are typical causes. It shows as loose, fluttering edges. Fixing edge wave in the slitting problems guide.
Ejector ring
A rubber or steel-backed ring next to each knife that pushes the freshly cut strip off the blade so it does not wrap the arbor. Also called a stripper ring. Worn ejector rings let strips climb and jam the head. Ejector rings guide.
Entry guide
Adjustable guides at the infeed that center the master coil and hold it square as it enters the slitter head. Poor entry guiding lets the strip walk sideways into the knives, which drifts width along the coil.
Fraction kit
A graduated set of thin precision metal spacers in small increments that lets the spacer stack land on an exact pocket width without loose plastic shims. Fraction kits are the basis of shimless setup. Fraction kits guide.
Gauge
The thickness of the metal being slit, often given as a decimal or a gauge number. Gauge drives knife clearance, overlap, and separating force, so it is the first number a crew checks when setting up a job.
Hold down
A roll or shoe that presses the strip down at the entry or exit to keep it flat and stop it lifting into the tooling. Hold downs help control threading and reduce edge damage on light gauge.
Knife overlap
How far the top and bottom knives pass each other vertically, also called penetration. Thin ductile metal needs more overlap to start the fracture; thick hard metal needs less. Too much overlap causes edge wave.
Looping pit
A pit between the slitter head and recoiler where the strips hang in a controlled loop, decoupling cutting speed from winding speed and keeping tension even. Common on light gauge, high speed lines.
Mandrel
The expanding shaft on an uncoiler or recoiler that grips the bore of a coil. It expands to lock the coil for payoff or rewind and collapses to load and strip finished coils off the line.
Master coil
The wide incoming coil that a slitting line cuts into narrower strips. Its width, gauge, and weight, along with the number of cuts, define the job and decide which line and tooling can run it.
Mult
A shorthand for the number of strips, or multiples, cut from one master coil in a single pass. A five mult job makes five strips. Cut count, or mults, drives arbor length and tooling needs.
Overlap
See knife overlap. The vertical distance the upper and lower knives pass each other, also called penetration. It works with horizontal clearance to start and complete the fracture that separates each strip.
Pass line
The height and horizontal path the strip follows through the line. A consistent pass line keeps the strip feeding straight and level into the knives; a pass line that steps up or down adds threading and flatness problems.
Penetration
How deep the upper knife reaches past the lower knife, the same idea as knife overlap. Correct penetration starts a clean fracture; too little leaves an incomplete cut, too much stretches and waves the edge.
Recoiler
The powered mandrel at the end of the line that rewinds each slit strip into its own tight coil. Tension, wrap tightness, and strip separation here decide whether the finished coils ship clean or get rejected.
Rewinder
A machine or the recoiler function that winds strip back into a coil. A plain rewinder respools a coil without slitting it, while a slitting line rewinds several narrower strips at once on the recoiler.
Rubber bonded spacer
A spacer with a rubber outer layer bonded to a steel core. It grips the strip and damps vibration but compresses under load, so it controls the strip rather than setting the critical width. Used with metal spacers. Rubber bonded spacers guide.
Scrap winder
A small recoiler that winds the edge trim and cutoff scrap into a coil for handling, instead of letting it pile up. Also called a trim winder. Keeps the line clear of loose scrap during a run.
Separator disc
A disc on the recoiler side that keeps finished strips apart as they rewind so they do not climb over each other and mar their edges. Disc flatness and thickness decide whether coils come off clean. Separator discs guide.
Shim
A thin loose ring stacked in a pocket to pad the spacer stack out to the exact target width. Shims work but add loose parts and tolerance error, which is why fraction kits and shimless setups replace them.
Side trim
Another term for edge trim, the scrap removed from the outer edges of the master coil to clean up the mill edge and set overall width. Side trim width is planned into the cut layout and yield.
Slit width
The finished width of a strip after slitting. The pocket built on the arbor equals the slit width minus one shared knife thickness across each boundary, which is why spacer accuracy drives width accuracy.
Slitter
On the shop floor, slitter can mean the whole slitting machine or the tooling assembly, the arbor loaded with knives and spacers. Context decides which: running the slitter versus building the slitter. What is a slitter.
Slitter head
The working zone of the line where the two arbors carry the knives and spacers that make the cut. Everything that decides width tolerance and edge quality happens here, so it is built with the most care.
Slitter knife
The circular rotary blade that shears the strip. Top and bottom knives pass with a set clearance and overlap to start a controlled fracture. Knives wear fastest of the precision tooling and shrink slightly at each regrind. Slitting knives guide.
Slitting line
The complete line that cuts a master coil into narrower strips: uncoiler, slitter head, tension or looping section, and recoiler. The line, not just the knives, is the unit that decides what tooling you run. Slitting machine and line guide.
Spacer
A precision ring loaded between knives to set each pocket width. Metal spacers carry the cutting force and set the critical dimension; rubber bonded spacers control the strip. Fewer spacers per pocket means less tolerance error. Metal spacers guide.
Strip
A single narrow band of metal produced by slitting a master coil. Each strip is rewound into its own coil on the recoiler. Strip width, edge quality, and flatness are the outputs the whole line is judged on.
Stripper ring
Another name for an ejector ring: a ring beside each knife that strips the cut strip off the blade so it does not wrap the arbor. Rubber rings suit light gauge; steel-backed rings handle higher force and heat. Ejector rings guide.
Tension stand
A driven set of pads or rolls that puts even pull on the strips after the cut so they stay flat and wind tight. Heavier or faster lines use a tension stand where light gauge lines use a looping pit.
Tolerance
The allowed band around a target dimension, most often the plus or minus range on strip width. Tighter tolerance demands better tooling, lower shaft runout, and fewer spacers per pocket to control cumulative error.
Top knife
The upper rotary knife in a slitting pair, carried on the top arbor. It overlaps the bottom knife by the set penetration and sits apart from it by the set clearance. Usually smaller in diameter than the bottom knife.
Turnstile
A rotating rack that holds several pre-built arbors or tooling sets so a crew can swap a full set into the head instead of building on the machine. Turnstiles and cassette heads cut changeover time.
Uncoiler
The payoff at the head of the line that holds the master coil on a mandrel and feeds it under back tension. If it cannot keep the coil centered, the strip walks into the knives and width drifts.
Width variation
Change in strip width along the coil or across a set of strips. It points to shaft deflection, worn spacers, a wandering strip, or drifting clearance. Center strips growing wide is a classic sign of arbor flex.
Yield
The share of the master coil that leaves as saleable strip rather than scrap. Edge trim, cut layout, and setup errors all cut into yield, so tighter planning and buildable setups protect margin on every coil.

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Related guides

Slitting line tooling guideEvery component on the arbor: shafts, knives, spacers, ejector rings, and fraction kits.Slitting machine guideHow coil slitting lines work, from line types to clearance and buying mistakes.How to choose rotary slitter bladesSpec, material, and sizing for the knives that ride on your shafts.