Large automotive dies and fixtures in a tool shop

Tooling: Molds, Dies, Jigs and Fixtures

November 7, 2026

In manufacturing, tooling means everything built to make a part rather than being the part: molds, dies, jigs, fixtures and gauges. Tooling is usually a one-time cost paid before production starts, and it decides the price of every part that follows. A good tool makes parts quickly and consistently for years; a poor one makes scrap, downtime and repairs. The basic trade is always the same: spend more on tooling and each part costs less to make.

Prototype, bridge and production tooling

Prototype tooling, sometimes called soft tooling, is built quickly and cheaply from aluminum, tooling board, composite or 3D printed inserts. It makes anywhere from a handful to a few thousand parts, enough to test the design in the real material and process.
Bridge tooling supplies parts for builds and early sales while the production tool is being made, so a launch doesn't wait on steel.
Production tooling is built from hardened tool steel to make hundreds of thousands or millions of parts with routine maintenance.

The right stage depends on volume and timing. See aluminum vs steel injection molds.

Injection molds

An injection molding machine melts plastic pellets and injects them under high pressure into a closed mold, where the plastic cools and is ejected as a finished part, often in under a minute. The mold has two halves: the cavity side, which forms the outside of the part, and the core side, which forms the inside and carries the ejector pins. Molten plastic flows through a runner and enters the part through gates. Water channels drilled through the steel carry the heat away, and slides and lifters form undercuts that would otherwise lock the part in the mold.

A mold's cost depends on part size and complexity, the number of cavities, the steel, the runner system and the surface finish. Our tooling guides cover each piece:

Mold classes

In North America, expected mold life is often specified with the SPI mold classes, now maintained by the Plastics Industry Association.

Class	Expected life	Typical use
101	Over 1,000,000 cycles	Very high volume production
102	Up to 1,000,000 cycles	Medium to high volume, abrasive materials or close tolerances
103	Up to 500,000 cycles	Medium volume production
104	Up to 100,000 cycles	Low volume, non-abrasive materials
105	Up to 500 cycles	Prototypes

Naming a class in your request for quote tells the toolmaker what steel, cooling and wear components to build in.

Compression molds

Compression molds are matched metal molds that close on a charge of material in a heated press. They're used for carbon fiber prepreg, sheet molding compound and rubber. A precise shear edge between the halves sets the edge of the part and lets excess resin escape. See compression molds for carbon fiber.

Die casting dies

Die casting injects molten aluminum, zinc or magnesium at high pressure into a hardened steel die, usually H13. It makes thin-walled metal parts with a good surface finish at high volume, such as housings and brackets. Die life is limited by heat checking, fine cracks caused by the die heating and cooling with every shot: often around 100,000 shots for aluminum, and many more for zinc, which casts at a much lower temperature.

Stamping dies

Stamping dies cut and form sheet metal in a press. A single-hit die does one operation per stroke. A progressive die feeds a coil strip through a series of stations, cutting and forming a little more at each one, so a finished part drops off with every stroke. A transfer die moves separate blanks between stations with mechanical fingers, which suits larger and deeper parts. Die sections are made from tool steels such as D2, or carbide for very long runs, and the die has to allow for the metal springing back after it's bent. See progressive vs transfer dies and springback in stamped parts.

Composite tooling

Carbon fiber and fiberglass parts are laid up on molds made from tooling board, fiberglass or carbon composite, aluminum or steel. Large aerospace parts cured in an autoclave often use Invar, an iron-nickel alloy that expands about as little as carbon fiber when heated. Matching the mold's thermal expansion to the part matters because the part is shaped hot and used cold. See how composite tooling steps up from prototype to production.

CNC router cutting a tooling board pattern

Jigs and fixtures

A fixture holds a part in a known position while it's machined, welded, assembled or inspected. A jig also guides the tool, like a drill jig with hardened bushings. In practice the two words are often used loosely.

Good fixtures follow the 3-2-1 rule: three points locate the part on its main face, two on a second face and one on a third, which fixes it in all six directions. Clamps then push the part against those locators, never away from them. Welding fixtures also have to resist the pull of the weld as it cools, and leave room for the torch. See jig vs fixture.

Gauges and checking fixtures

Go/no-go gauges check a feature in seconds without reading a number: if the go end fits and the no-go end doesn't, the feature is in tolerance. Plug, ring and thread gauges are the common types. A checking fixture holds a formed part, such as a stamped or molded car part, in its in-car position so trim edges, surfaces and holes can be checked quickly on the production floor. A common rule of thumb is that a gauge should be made to about 10 percent of the tolerance it checks. See checking fixtures for automotive parts and precision tooling for high-volume production.

Who owns the tool

In most custom manufacturing the customer pays for the tooling and owns it, while the supplier stores, runs and maintains it. Agree up front on who pays for maintenance and repairs, what happens when the tool wears out, and how it can be moved to another supplier. Automotive programs usually approve new tooling through PPAP (production part approval process) before parts ship.

What drives tooling cost and lead time

Part size, which sets the size of the steel and the press.
Complexity: undercuts that need slides or lifters, tight tolerances, and textured or polished surfaces.
The number of cavities or stations.
Steel grade and hardness, set by the expected life and the material being processed.
Design reviews, simulation, and the number of trial rounds before approval.

For a mold, die or fixture, see our tooling page, or send the drawing with your annual volume and we'll suggest a suitable level of tooling.

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