Tooling and jig plate is aluminium plate or block bought for flatness and dimensional stability first, and strength second. The right choice depends on whether your part is a thin, flat fixture base (cast, precision-milled plate), a stressed or welded tooling structure (rolled 5083 or 6061-T651), or a deep-machined mould or block (thick 6061, 7075 or forged block). This guide explains each route, the numbers that matter and how to order.
A jig holds and guides a cutting tool; a fixture locates and clamps a workpiece. Both, along with inspection plates, vacuum tables, machine bases and mould plates, depend on one property more than any other: the plate must be flat when it arrives and stay flat after you machine it.
Ordinary rolled plate is quenched from a high temperature during heat treatment. The quench leaves the surface in compression and the core in tension. When a machinist removes metal from one face, that balance is disturbed and the plate bows. Tooling plate products tackle the problem in two ways. Cast tooling plate is produced from a slab that is never quenched, so internal stress is very low from the start; it is then stress-relieved and milled flat on both faces. Rolled tooling plate, such as 6061-T651 or 7075-T651, is stretched by a controlled 1.5 – 3 % after quenching so that most residual stress is removed mechanically.
The term "jig plate" in the market almost always refers to the cast, precision-milled product, often bought by the sheet in imperial thicknesses from 1/4 in to 4 in. "Tooling block" usually means thicker material, from about 50 mm upward, used for mould bases, deep cavities and large machined parts, and sawn from very thick plate or from a forging.
Continuously or DC-cast slab, thermally stress-relieved and milled on both faces, then film-protected. Very stable and flat, typically supplied 6 – 100 mm (1/4 – 4 in). Lower strength and elongation than wrought plate. Proprietary versions are sold under brand names such as MIC-6®, ATP-5® and Alca 5®; buyers often ask for a generic equivalent.
Non-heat-treatable, so there is no quench stress. Machines and welds well, has good corrosion resistance and is often supplied in a cast-and-milled or H111 condition for fixtures, welded jigs and vacuum tables.
Stretched heat-treated plate. Roughly twice the strength of cast plate, good machinability and an excellent anodising response. The usual choice for loaded fixtures, machine frames and plates that must be tapped and bolted repeatedly.
High-strength plate for injection-mould cavities, blow moulds and parts that need a hard, wear-resistant surface. Thick plate is widely used for prototype and short-run moulds because it machines very fast.
Thick sections, typically 50 – 600 mm, sawn from plate or forging. Ordered for mould bases, deep-pocket parts and large monolithic components. Specify stress-relieved material and check the certificate for through-thickness properties.
Open-die forged 6061, 7075 or 2024 block, used when a thick part needs finer grain and better properties in the short-transverse direction than plate can offer. See our forged block page.
Values below are typical, not guaranteed minimums. For cast tooling plate, producers publish only typical data, and the figures differ slightly between brands and alloys, so always design to the certificate or producer datasheet for the exact product you buy. Wrought-plate figures are standard Aluminum Association typical values.
| Property | Cast precision plate (typical range) | 5083-H111 | 6061-T651 | 7075-T651 |
|---|---|---|---|---|
| Tensile strength | about 165 – 220 MPa (24 – 32 ksi) | 290 MPa | 310 MPa | 570 MPa |
| Yield strength (0.2 %) | about 105 – 140 MPa (15 – 20 ksi) | 145 MPa | 276 MPa | 505 MPa |
| Elongation | about 3 % | 22 %+ | 12 % | 11 % |
| Brinell hardness | about 65 – 70 HB | 75 HB | 95 HB | 150 HB |
| Residual stress | Very low (no quench) | Very low (no quench) | Low (stretched) | Low (stretched) |
| Weldability | Fair to good, depends on alloy | Excellent | Good | Poor |
| Anodising response | Functional; colour may be uneven | Fair | Excellent | Good |
Cast tooling plate figures summarise published producer datasheets for commercial cast plate; check the specific product data before design.
The practical message is simple. Cast plate trades strength for stability: use it where the part is located, clamped and measured, not where it carries high loads. When a fixture is bolted to a machine table and loaded by cutting forces, or when holes are tapped and threads reused hundreds of times, the extra strength and hardness of 6061-T651 or 7075-T651 make a difference.
Cast precision plate is milled on both faces, which gives a tight thickness tolerance (commonly about ±0.13 mm / ±0.005 in), close flatness and a fine machined finish in the region of Ra 0.5 – 0.8 µm (20 – 32 µin). Rolled plate is supplied to the standard mill tolerances of ASTM B209 or EN 485, which are much wider; if you need rolled plate to tooling-plate accuracy, order it precision-milled or fly-cut.
| Characteristic | Cast precision plate | Rolled plate as supplied | Rolled plate, precision milled |
|---|---|---|---|
| Thickness tolerance | Tight (milled) | Mill tolerance per ASTM B209 / EN 485-3 | Tight, to order |
| Flatness | Close; held after machining | Mill flatness; T651 holds shape when machined | Close, to order |
| Surface | Fine milled finish both sides | Mill finish, may show handling marks | Fine milled finish |
| Protection | PVC or paper film both faces | Interleaving or film on request | PVC film |
| Typical thickness | 6 – 100 mm (1/4 – 4 in) | 6 – 250 mm and above | To suit |
When writing a purchase order, state flatness as a value over a length (for example 0.1 mm per 1000 mm), state parallelism if two faces must agree, and say whether the tolerance applies before or after you machine the part. Be careful when comparing quotes: one supplier may quote flatness per foot, another per metre, another over the full plate.
Weight is calculated from density. Most rolled plate is about 2.70 g/cm³; cast tooling plates are slightly heavier at roughly 2.7 – 2.8 g/cm³ because of their alloy content. The table uses 2.70 g/cm³ for comparison; check the producer density for exact cast-plate weights.
| Thickness | mm | kg per m² | kg, 1250 × 2500 mm | lb per ft² |
|---|---|---|---|---|
| 1/4" | 6.35 | 17.1 | 53.6 | 3.51 |
| 3/8" | 9.52 | 25.7 | 80.4 | 5.27 |
| 1/2" | 12.70 | 34.3 | 107.2 | 7.02 |
| 5/8" | 15.88 | 42.9 | 133.9 | 8.78 |
| 3/4" | 19.05 | 51.4 | 160.7 | 10.53 |
| 1" | 25.40 | 68.6 | 214.3 | 14.05 |
| 1-1/4" | 31.75 | 85.7 | 267.9 | 17.56 |
| 1-1/2" | 38.10 | 102.9 | 321.5 | 21.07 |
| 2" | 50.80 | 137.2 | 428.6 | 28.09 |
| 2-1/2" | 63.50 | 171.5 | 535.8 | 35.11 |
| 3" | 76.20 | 205.7 | 642.9 | 42.14 |
| 4" | 101.60 | 274.3 | 857.2 | 56.18 |
| Application | Usual choice | Why |
|---|---|---|
| CNC fixture plates, sub-plates, drill jigs | Cast precision plate | Stays flat when pockets are cut; no need to skim before use |
| Inspection and CMM base plates | Cast precision plate | Stability over time matters more than strength |
| Vacuum tables and router plates | Cast plate or 5083 | Flat, easy to drill hundreds of holes, no distortion |
| Welded jigs and assembly frames | 5083 or 6061-T651 | Good weldability; 5083 keeps strength in the weld zone |
| Loaded machine bases, gantries | 6061-T651 or 6082-T651 | Higher yield strength and stiffness per kg |
| Injection and blow moulds, prototype tools | 7075-T651 or thick 6061-T651 | Fast machining, good surface, hardness for wear |
| Deep-cavity mould bases, large blocks | Thick plate block or forged block | Properties through the full section |
| Semiconductor and vacuum fixtures | 6061-T651, 5083 | Clean machining, anodising, vacuum compatibility |
A common mistake is to order cast jig plate for a part that is really structural, such as a bracket that carries a cantilevered load, and then see it crack at a tapped hole. The opposite mistake is ordering standard 6061-T6 mill plate for a thin fixture and spending hours skimming both faces flat. For background on the two main rolled grades, see 6061 plate and block for CNC machining and our comparison 6061 vs cast tooling plate.
All of these products machine well with sharp carbide, high spindle speeds and flood coolant or mist. Remove material symmetrically from both faces where possible, rough first, let the part rest, then finish. That habit gets the most from even the most stable plate.
Thin cast plate is soft compared with T651 plate; spread clamping forces and avoid over-tightening, which can dent the surface and spoil flatness.
In cast plate and other low-strength material, specify thread inserts for threads that will be assembled often. In 6061-T651 and 7075-T651, tapped threads hold well.
5083 welds very well with ER5183 or ER5356 filler. 6061 welds with ER4043 or ER5356, with a softer heat-affected zone. Weldability of cast tooling plate depends on its alloy; check the datasheet. 7075 is not considered fusion-weldable.
6061-T651 gives the most even decorative anodised colour. Cast plate takes clear and hard anodic coatings for wear and corrosion protection, but colour may be blotchy. Ask before specifying colour anodising.
Store plate flat on even supports, keep the film on until machining and remove film from both faces at the same time to avoid uneven temperature during cutting.
Jig plate is usually cast, stress-relieved and milled on both faces, so it is flat, has a tight thickness tolerance and stays flat when machined. Normal rolled plate has wider mill tolerances and, unless it is a stretched T651 temper, may distort as material is removed.
Generally not for highly loaded parts. Typical tensile strength is around half that of 6061-T651 and elongation is only about 3 %. Use it for fixtures, bases and templates, and choose 6061-T651, 6082-T651 or 7075-T651 for parts that carry significant load.
Yes, cast and precision-milled tooling plates from other producers serve the same purpose. Compare thickness tolerance, flatness, surface finish and alloy on the datasheet rather than assuming two products are identical.
7075-T651 is the most common choice for aluminium injection moulds because of its hardness and strength; thick 6061-T651 is used for less demanding tools. Check that the plate is stress-relieved and has consistent properties through its thickness.
Yes. Clear and hard anodising work on most tooling plates. For an even decorative colour, 6061-T651 performs best; cast plate can look uneven when dyed.
Yes. Metline supplies tooling plate in metric and imperial thicknesses, full sheets or cut to size, with mill certificates and export packing to customers worldwide.
Tell us the part, flatness and quantity. We will recommend cast, rolled or forged stock and quote a delivered price.
