Metal Working Terms

Metal Working TermsSpeak the language

Terms you'll run into on our install guides, our shop videos, and any time we talk through a repair on the phone. This is traditional panel-beating and fabrication language — the vocabulary of shaping and joining sheet steel by hand, the way body men have done it for a hundred years and the way we still do it in Orange.

Reading the Metal Hand Tools & Panel Beating Shaping Machines Joining & Welding Body Solder & Filler Related Terms Worth Knowing

Reading the Metal

The concepts behind why the tools exist

Contour: The three-dimensional shape a panel is supposed to hold — its intended surface, independent of any single dent or high/low spot. "Working to contour" means shaping toward that original form rather than just chasing flat, since a fender or roof skin is never actually flat — it's a deliberate curve, and metal finishing succeeds or fails by how closely it returns to that shape.
Crown: The amount of curve in a panel. High crown means a lot of curve in a small area (a fender edge, a rounded corner); low crown means a broad, gentle curve (a hood, a roof skin, a door skin). Low-crown panels are far less forgiving — small errors show as waves across a wide, flat-looking area, which is why hoods and doors are some of the hardest panels to get right.
High Spot / Low Spot: The peaks and valleys in a panel's surface once it's been dented or worked. Identifying these accurately — usually by feel, by eye under raking light, or with a body file — is most of the actual skill in metal finishing. You can't fix what you can't find.
Oil Canning: The wavy, flexible "pop in, pop out" condition in a flat or low-crown panel, named for the way an old-fashioned oil can's bottom flexes when pressed. It happens when a panel has lost its crown — usually from being over-stretched — and no longer holds tension across its surface. Oil canning isn't fixed by hammering harder; it's usually fixed by shrinking the panel back to size (see Shrinking Disc).
Grain (Metal Grain): The direction sheet steel was rolled at the mill. Steel is slightly stronger and more resistant to stretching along the grain than across it. Matters most when you're fabricating a patch panel from flat stock — orienting the grain to match the panel you're replacing gives a stronger, better-behaved repair.
Stretching: Working metal so it covers more surface area than it started with — which happens automatically any time metal is bent, dented, or hammered directly (see Hammer-on-Dolly). A dent is stretched metal; that's why dents don't just pop back to flat, and why panel repair is as much about un-stretching metal as it is about un-bending it.
Shrinking: The opposite of stretching — reducing a panel's surface area back down after it's been over-stretched. Done by controlled heating and rapid cooling (see Shrinking Disc), which causes the heated area to contract more than the surrounding cold metal allows it to expand.
Work Hardening: What happens to sheet steel as you hammer, bend, or flex it repeatedly — it gets stiffer and more brittle in the worked area. Push it too far and the metal cracks instead of moving. This is why panel beating is done in controlled, incremental passes rather than a few heavy blows: give the metal a chance to move without hardening past the point of no return.
Annealing: Heating metal to relieve work hardening and restore its softness/ductility, allowing further shaping without cracking. Common on aluminum panels, which work-harden faster than steel.
Form and Shape: Two sides of the same job. Shape is the target geometry you're chasing — see Contour and Crown. Form is the physical reference you check that shape against as you work: a buck, a die, the mating panel, or just your eye and hand. Shaping without something to form to is guesswork; a form nobody's shaping metal to is just a pattern.

Hand Tools & Panel Beating

What actually sits on the bench

Dolly: A dense, shaped steel hand tool held against the back side of a panel to back up hammer blows from the front — or vice versa. Dollies come in many profiles (heel, toe, egg, comma, etc.) to match different panel curves; the shape of the dolly you choose should roughly match the crown of the area you're working.
Hammer-on-Dolly: Striking the panel directly opposite where the dolly is held. This stretches the metal at the point of impact — useful for moving metal into a low spot, but overused it will over-stretch a panel and cause oil canning.
Hammer-off-Dolly (Hammer-off): Striking the panel slightly to the side of where the dolly is held, rather than directly opposite it. This uses the dolly as a lever to bring high spots down without stretching the metal further — the technique most metal finishers reach for first, since it corrects shape without adding the stretch that hammer-on-dolly work does.
Slapper (Slapping Spoon): A long, flat, slightly curved steel tool used to strike broad areas of a panel — spreading force over a wider area than a hammer face would, useful for working large, gentle high spots down without concentrating the blow into a new low spot.
Pick Hammer: A hammer with a pointed or chisel-shaped head opposite the flat face, used to raise small, isolated low spots from behind the panel — "picking" a dent up from the inside rather than pounding it down from the front.
Body File / Vixen File: A file with curved-cut teeth (rather than straight rows) designed to skim across a panel's high spots while leaving low spots untouched — the shine pattern the file leaves behind shows you exactly where the metal still needs work before you move to a hammer and dolly again. "Vixen" is a specific curved-tooth pattern that's become the generic term for this style of body file in most shops.
Pick and File: The classic diagnostic-and-correction cycle in metal finishing: file the panel to reveal high and low spots by the shine pattern, pick or hammer the low spots up, file again, repeat — working the panel true before any filler goes anywhere near it.
Planishing: Fine, light hammer work (often with a planishing hammer — a powered or hand tool with two opposing dies) done after rough shaping, to smooth out the small hammer marks and true up the final surface. The last hammer step before metal finishing with a file.
Tipping (Tipping an Edge): Bending or rolling the outer edge of a panel over — by hand, with a hem tool, or over a form — to hide the raw edge, stiffen the panel, or create a lip that mates with another panel. Common on door skins, hood edges, and wheel arch lips; a close relative of hemming, and one of the last steps before a panel's edge is finished.
Shrinking Disc: A smooth (non-abrasive) stainless steel disc mounted on a grinder or polisher. Spun against a high spot, friction generates heat quickly; a damp rag or light water mist then cools it fast, causing the heated steel to contract. Far more controllable than shrinking with an open torch, since the heat stays concentrated on the actual high spot instead of spreading across the whole panel. The standard modern tool for correcting oil canning and over-stretched metal without filler.
Stud Welder / Slide Hammer: A stud welder tacks small pins to the face of a dent; a slide hammer (or a dedicated dent-puller attachment) then hooks onto those pins and pulls the low spot back out, without needing access to the back side of the panel. Common on quarter panels and other areas you can't reach a dolly into.
Joggle / Flange: A joggle is a stepped offset pressed into a panel edge so it sits flush against an adjoining unstepped panel — common on repair panels that need to blend into original metal without a visible ridge. A flange is a bent-over edge on a panel, either rolled for stiffness or left flat as a mating surface for the next panel to weld or bond to. Most patch panels carry both: a flange to join to, joggled where it needs to sit flush.

Shaping Machines

How flat sheet becomes a compound curve

English Wheel: A large stand-mounted machine with two rollers — a flat lower anvil wheel and a curved upper wheel — that a panel is rolled between under pressure. Passing metal through repeatedly, adjusting the gap and the path, gradually stretches and shapes it into a smooth compound curve. The traditional way to hand-form large curved panels (fenders, hoods, nose cones) from flat sheet, and still the standard in shops doing this work the old way.
Bead Roller: A machine with a pair of matched rollers that forms a raised bead or reinforcing rib into a flat panel as it's cranked through — used both for cosmetic body lines and for stiffening a flat repair panel so it doesn't oil can.
Shrinker / Stretcher (Jaws): Hand or pneumatic tools with jaws that either compress (shrinker) or spread (stretcher) the edge of a panel in small bites — used for shaping flanges and curves in flat stock before it goes anywhere near an English wheel, especially on tight radius work like wheel-arch lips.

Joining & Welding

How the metal gets connected

TIG Welding (GTAW – Gas Tungsten Arc Welding): Welding using a non-consumable tungsten electrode to create the arc, shielded by inert gas (typically argon), with filler metal fed in separately by hand if needed. Produces the cleanest, most controllable weld of the common processes — the standard choice for thin sheet metal body work and repairs where the weld needs to be ground and finished invisibly.
MIG Welding (GMAW – Gas Metal Arc Welding): Welding using a continuously-fed wire electrode that also serves as the filler metal, shielded by gas. Faster than TIG and easier to learn, but generally less precise on thin sheet — more common for structural/chassis work than for finish body panels.
Cleco: A spring-loaded, removable fastener used to hold two drilled sheet metal panels in alignment before final riveting or welding — squeeze the pliers, drop the pin through matching holes, release, and it clamps the panels flush. Pulls back out and reuses indefinitely, unlike a rivet or tack weld, which makes it the standard way to fit and re-check a patch panel or skin repeatedly before committing to anything permanent.
Gas Welding / Torch Welding (Oxy-Acetylene): Welding using a flame from burning oxygen and acetylene together, with filler rod melted into the joint by hand. The oldest of these processes and still useful for its controllability at low heat — also the same equipment used for brazing, torch shrinking, and simply heating a stubborn part.
Brazing: Joining metal by melting a filler alloy (traditionally bronze or brass) that flows into the joint at a lower temperature than the base metal's melting point — the base metal itself never melts. Produces a strong joint with less heat distortion than welding, historically common on the very sheetmetal this shop specializes in.
Tack Weld: A short, small weld placed to hold two pieces of metal in position before the final, full weld is run — lets you check fit and alignment (like a door gap) before committing.
Filler Rod: The metal rod fed into a weld puddle by hand (in TIG or gas welding) to add material to the joint, as opposed to processes like MIG where the filler is built into the continuously-fed wire.
Lap Weld / Butt Weld: Two ways to join panel edges. A lap weld overlaps one edge over the other before welding — stronger and more forgiving of gaps, but leaves a visible ridge unless ground flush. A butt weld joins two edges flush, edge to edge — cleaner-looking when finished but less forgiving of gaps and requires more precise fit-up beforehand.
Plug Weld: A weld made by drilling or punching a hole through the top layer of an overlapped joint, then filling it with weld metal to fuse it to the panel underneath — the way to replicate a factory spot weld where a spot welder can't reach or the stack is too thick for one. Common on rocker panels, floor pans, and anywhere a lap joint needs the strength of a spot weld without spot-welder access.

Body Solder & Filler

The traditional way to finish, no filler

Lead / Lead Loading / Body Solder: The original body filler: a lead-tin alloy melted with a torch and worked into shape by hand with a wooden or wax paddle while still soft, then filed smooth. Predates plastic body filler by decades and was the factory-correct finishing method on many of the cars we work on — still used here where correctness matters more than convenience.
Tinning: Coating bare metal with a thin layer of solder (or, in a welding context, flux/filler) so a subsequent material — lead, solder, another metal — will properly bond to it. A required prep step before lead loading; lead won't stick to bare untreated steel.
Metal Finishing: Working a panel with hammer, dolly, and file until it's true and smooth enough to prime directly, with no filler at all — the traditional standard this whole glossary is built around, and the reason all of the above tools and terms exist.

Dykem: A blue (or sometimes red) layout fluid brushed or sprayed onto bare metal, dried to a thin coating that a scribe cuts cleanly through — the scratched line shows bright silver against the color, far easier to see and follow than a pencil or marker line on raw steel. Standard prep before scribing a cut line, a hole location, or a fit-up mark on a patch panel.
Scribe: A hardened steel hand tool with a sharp point, used to mark cut lines, fold lines, or fit-up reference marks directly into (or through) a coating on metal — see Dykem. Cuts a permanent, precise line that won't rub off or wander the way a pencil or marker can.
Debur: Removing the sharp, raised edge (the burr) left behind after cutting, drilling, or punching sheet metal — with a deburring tool, file, or sanding disc. Left in place, a burr snags gloves, keeps a Cleco or panel from sitting flush, and gives paint a sharp edge to crack along later. A quick step, easy to skip, and one of the fastest ways to tell rushed work from careful work.
Stationary Panel: A body panel that's permanently welded or bolted solid to the car's structure — a quarter panel, roof skin, or rocker, as opposed to a closure panel (door, hood, deck lid) that hinges open. The distinction changes the repair approach: closures usually come off and go to the bench, while stationary panels get worked in place, on the car.
Gapping: Adjusting a panel's fit — shifting the hinges, striker, or mounting points — until the space between it and the surrounding panels is even, consistent, and matches spec all the way around. The step that turns a door or hood from merely closing to closing right.
Buck: A shaped wood or metal form used as a reference or support while hand-forming a panel over the English wheel, helping you match a specific target shape rather than working freehand.
Guide Coat: A thin, contrasting-color dusting of primer or powder sprayed over a panel before final sanding — sands off the high spots first, leaving color in the lows, so you can see exactly what's still not flat before you commit to paint.
Quench: Rapidly cooling heated metal — with water, a damp rag, or air — to lock in a shrink or to control how the metal's grain structure sets after heating.

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