Cast tool and jig plate exists because it can be made flat and stay flat, but it has about half the tensile strength of 6061, it welds badly, and it anodizes blotchy. Answer six questions about your part and this tool tells you which plate to buy, with the tradeoff numbers side by side instead of a forum argument.
Last updated July 2026
| Option | As supplied, in | Per foot | Move after cut, in | Meets target |
|---|---|---|---|---|
| Cast tool and jig plate | 0.0150 | 0.0075 | 0.0001 | no |
| 6061-T651 | 0.0500 | 0.0250 | 0.0009 | no |
| 7075-T651 | 0.0500 | 0.0250 | 0.0017 | no |
The 0.015 in cast figure is a whole-plate guarantee, so over a short span the real deviation is usually far less than the number shown. Movement is a first-order estimate of midspan bow from releasing residual stress, not a simulation. Leave stock and rough-then-rest either way, and size the blank with the raw stock size optimizer.
| Option | Cost per lb | Order nominal, in | Cost per part |
|---|---|---|---|
| Cast tool and jig plate | 1.40x | 1.000 | 1.13x |
| 6061-T651 | 1.00x | 1.250 | 1.00x |
| 7075-T651 | 2.10x | 1.250 | 2.18x |
Cast plate holds plus or minus 0.005 in on thickness and arrives flat, so you order it at the finished nominal. Rolled plate has to clear its own minus tolerance plus a cleanup cut on each face, which normally costs you one nominal step. That is why a 1.40x per pound premium lands closer to 1.13x per finished part.
| Your answer | Cast | 6061 | 7075 |
|---|---|---|---|
| Fixture, subplate or jig | 4 | 1 | 0 |
| Flatness 0.005 in per foot | 3 | 0 | 0 |
| Light skim both faces, under 10 percent | 0 | 1 | 1 |
| Total | 7 | 2 | 1 |
This is a weighted rule engine, not a physics model. It encodes the tradeoffs shops argue about so the argument happens once, in the open, with the numbers visible.
1 pc 5000 series cast tool and jig plate, 1.000" nominal +/-0.005" x 24" x 24", cast, thermally stress relieved, machined both faces, flat within 0.015" over the plate, finished thickness 1.000", mill cert and DFARS domestic melt required.
| Property | 5000 series cast tool and jig plate | 6061-T651 | 7075-T651 |
|---|---|---|---|
| Base alloy | Cast aluminum-magnesium, roughly 5xxx chemistry. ALCA-5 class is a modified 5083 type | Wrought Al-Mg-Si | Wrought Al-Zn-Mg-Cu |
| Product route | Cast, thermally stress relieved, machined both faces | Rolled, solution treated, quenched, stretched 1.5 to 3 percent | Rolled, solution treated, quenched, stretched |
| Ultimate tensile, psi | 23,000 typical | 45,000 typical (42,000 min, B209) | 83,000 typical (78,000 min, B209) |
| Tensile yield, psi | 12,000 typical | 40,000 typical (35,000 min, B209) | 73,000 typical (68,000 min, B209) |
| Elongation, percent | 3 typical | 8 to 10 min | 5 to 7 min |
| Brinell, typical | 65 | 95 | 150 |
| Density, lb per cubic inch | 0.098 | 0.0975 | 0.101 |
| As-supplied flatness | 0.015 in over the whole plate, guaranteed | Commercial B209, up to about 0.20 in on a 48 in wide 1 in plate | Same as 6061 |
| Thickness tolerance | Plus or minus 0.005 in | ASTM B209 band, about plus or minus 0.035 in at 1.000 nominal | Same as 6061 |
| Residual stress | Essentially none | Low, roughly 1.5 ksi peak | Moderate, roughly 3 ksi peak |
| Stability after machining | Excellent, stays about as flat as it started | Good | Fair, moves about twice as much as 6061 |
| Machinability | Excellent, chips break clean, watch for porosity in a finished surface | Good, gummy, wants sharp polished tooling | Excellent chip breaking in T651 |
| Weldability | Poor, porosity and cracking, not recommended | Good with 4043 or 5356 filler | Not recommended, crack sensitive |
| Anodize response | Poor, blotchy, varies heat to heat. ALCA-5 class looks better than Mic-6 class | Very good, the reference material | Good, comes out darker, hard coat builds slower |
| Relative cost per pound | 1.40x | 1.00x | 2.10x |
Tensile and yield for the wrought alloys are typical values with the ASTM B209 minimum in parentheses. Buy to the minimum, design to the minimum, expect the typical.
They are competing cast tooling plate products of the same class with near-identical published flatness and thickness specs. Both are cast, then stress relieved, then machined on both faces. The real differences show up in anodize appearance and lot-to-lot consistency, not in strength or flatness.
It is not. QC-10 is a wrought 7000 series mold plate and it belongs in the 7075 and 7050 column, not the cast column. If someone tells you to use QC-10 instead of Mic-6 for flatness, they are recommending a different product category with roughly three times the tensile strength and a different price.
Cast tool plate is about half the tensile strength of 6061 and about a quarter of 7075. That is the price of the flatness. It is a different alloy family on a different product route, not a premium grade of the same thing.
Above 2.000 in, specify 7050-T7451 instead of 7075-T651. 7075 is quench sensitive and loses core properties as section thickness goes up. 7050 was designed for exactly that problem and holds its properties through the thickness.
| Material | Product route | Tensile, psi | Yield, psi | Brinell | Density, lb/in3 | As-supplied flatness | Cost per lb | Where it belongs |
|---|---|---|---|---|---|---|---|---|
| Cast tool and jig plate, Mic-6 class | Cast, stress relieved, faced | 23,000 typ | 12,000 typ | 65 | 0.098 | 0.015 in over plate | 1.40x | Fixture plates, subplates, jigs, checking fixtures |
| Cast tool and jig plate, ALCA-5 class | Cast, stress relieved, faced | 23,000 typ | 12,000 typ | 65 | 0.098 | 0.015 in over plate | 1.40x | Same as Mic-6 class, better anodize appearance |
| 6061-T651 | Rolled, quenched, stretched | 45,000 typ / 42,000 min | 40,000 typ / 35,000 min | 95 | 0.0975 | Commercial, about 0.20 in at 1 in x 48 in | 1.00x | General plate, welded parts, anodized parts |
| 7075-T651 | Rolled, quenched, stretched | 83,000 typ / 78,000 min | 73,000 typ / 68,000 min | 150 | 0.101 | Commercial, same grid as 6061 | 2.10x | Structural and high load parts up to 2.000 in |
| 7075-T7351 | Rolled, overaged, stretched | 73,000 typ | 63,000 typ | 135 | 0.101 | Commercial, same grid as 6061 | 2.25x | Marine and humid service, stress corrosion resistance |
| 7050-T7451 | Rolled, overaged, stretched | 76,000 typ | 68,000 typ | 140 | 0.102 | Commercial, same grid as 6061 | 2.50x | Thick sections over 2.000 in, aerospace structure |
| 7000 series mold plate, QC-10 class | Rolled, wrought, NOT cast | 74,000 typ | 64,000 typ | 140 | 0.102 | Mold plate grade, tighter than Commercial | 2.60x | Mold bases and high polish tooling, often confused with Mic-6 |
| 5083-H321 | Rolled, strain hardened | 46,000 typ | 33,000 typ | 82 | 0.096 | Commercial | 1.30x | Welded marine structure, the wrought cousin of cast tool plate |
| 2024-T351 | Rolled, naturally aged, stretched | 68,000 typ | 47,000 typ | 120 | 0.100 | Commercial | 1.80x | Fatigue critical aerospace parts, poor corrosion resistance |
Typical values are what a mill cert usually reports. Minimum values are the ASTM B209 guarantee for the temper and thickness range, and they are the only numbers you should design to. Cost per pound is indexed against 6061-T651 at 1.00 and moves with market and quantity. Note that QC-10 class mold plate sits in this table as a wrought 7000 series product, not a cast one.
Hard disqualifications run first. Welding removes 7075-T651 and flags cast plate. Appearance anodize flags cast plate. High load tapped holes in material under 0.750 inch remove cast plate. A marine environment on a load-bearing part removes 7075-T651 and substitutes 7075-T7351, or 7050-T7451 above 2 inches. Whatever survives is then scored, starting from zero, on use case, flatness requirement, span, thickness, material removal, tapped holes and finish. Highest score wins and the score margin sets the confidence line.
rolled deviation = Commercial grid value at your thickness x (span / 48)^2
cast deviation = 0.015 in over the whole plate, not span scaled
target deviation = flatness per foot x (span / 12)
Rolled plate bow scales with the square of the length you measure across, which is why a plate that looks fine on a 12 inch subplate is unusable as a 60 inch bed plate. The cast figure is a whole-plate guarantee, so over a short span the real deviation is normally far below 0.015 inch.
midspan bow = (peak residual stress / elastic modulus) x removal fraction x span^2 / (8 x thickness)
Peak residual stress is taken as roughly 200 psi for cast and stress relieved tool plate, 1,500 psi for stretched 6061-T651 and 3,000 psi for stretched 7075-T651. Removal fraction is 0.08 for a light skim, 0.25 for moderate removal and 0.55 for heavy or one-sided pocketing. This is a first-order estimate of the bow you release, not a simulation.
cost per part = cost per pound x (ordered nominal / finished thickness) x density ratio
rolled ordered nominal = smallest standard nominal where nominal minus B209 thickness tolerance minus 0.020 in cleanup is still at or above the finished thickness
cast ordered nominal = smallest standard nominal at or above the finished thickness
Cost per pound runs 1.00 for 6061-T651, 1.40 for cast tool and jig plate, 2.10 for 7075-T651 and 2.50 for 7050-T7451. Because cast plate holds plus or minus 0.005 inch and arrives flat, it usually orders one nominal thinner than rolled plate for the same finished dimension, which is why the 1.40x per pound premium typically lands near 1.13x per finished part.
Once the selector names a plate, the next question is what a blank actually costs at your size. Get an instant quote on 6061, 7075 and 7050 plate cut to your fixture size, DFARS domestic material with mill certs on every order.
Very little on paper. Both are 5000 series cast aluminum tooling plate, cast then thermally stress relieved then machined on both faces, and both are supplied flat within about 0.015 inch over the whole plate at plus or minus 0.005 inch thickness. They are competing products of the same class, not different materials. The differences shops actually notice are in anodize appearance and lot-to-lot consistency, where ALCA-5 class material generally behaves better.
For a fixture, usually yes. Cast tool and jig plate arrives flat within 0.015 inch over the whole plate against roughly 0.20 inch for Commercial grade rolled 6061, holds plus or minus 0.005 inch on thickness, and carries almost no residual stress so it stays flat after you cut pockets in it. The tradeoff is strength: about 23 ksi tensile against 45 ksi for 6061-T651. Use 6061 when the plate carries load, gets welded, or gets anodized.
Mic-6 class cast tooling plate is a cast aluminum-magnesium alloy in the 5000 series family, not a heat-treatable 6000 or 7000 series alloy. That is why it cannot be strengthened by heat treatment, why it runs about 23 ksi tensile and 12 ksi yield, and why it stays dimensionally stable. It is cast rather than rolled, which is the whole reason it has no rolling stress to release when you machine it.
No, and this is the most common mix-up in the category. QC-10 is a wrought 7000 series mold plate, not a cast product. It has roughly three times the tensile strength of Mic-6 class cast plate and belongs in the same column as 7075 and 7050. If a shop recommends QC-10 as an alternative to Mic-6 for flatness, they are proposing a different product category at a different price point, not a like-for-like swap.
You can, but expect blotchy and inconsistent results. Cast plate has a non-uniform grain structure, chemistry varies between heats because of the scrap content in the melt, and porosity can trap acid, so the coating builds unevenly and the color shifts lot to lot. If the part must be anodized for appearance, machine it from wrought 6061-T651 instead. If it is a fixture that just needs corrosion protection, chem film is the practical answer.
For fixtures with real flatness requirements, usually yes, and by less than the per-pound premium suggests. Cast tool and jig plate runs roughly 1.4 times 6061 per pound, but because it holds plus or minus 0.005 inch on thickness you can order it one nominal thinner for the same finished dimension, which recovers 10 to 20 percent of that. Add the second op you do not have to run to flatten it and the premium usually pays for itself.