Mill plate is made to a tolerance band, not to nominal, and the band is wider than most buyers expect. This tool shows the published thickness tolerance and the realistic as-received range for your nominal and width, then works backward from your finished thickness to tell you which nominal to actually put on the purchase order.
Last updated July 2026
Mills bias toward the upper half of the band on purpose. Undersize plate gets rejected and remelted, oversize plate ships and gets invoiced by weight. Plan the buy off the high end, plan the cleanup off the low end. 0.500 nominal typically arrives 0.505 to 0.520 in.
No blank length entered, so the flatness allowance falls back to a flat 0.010 in per face. Enter a blank length to scale it off real bow.
Vertical scale is proportional to the maximum as-received thickness. The white outline is the finished part. Everything between the white outline and the inner solid line is what the mill tolerance forces you to machine away.
6061-T651 aluminum plate, 0.625 in nominal thickness | Spec: ASTM B209, AMS-QQ-A-250/11 | Thickness note: material may run the high side of the tolerance band. Minimum acceptable as-received thickness 0.602 in, maximum 0.648 in. Part finishes at 0.450 in after machining both faces. | Mill certs required with shipment.
Tolerance grid as of July 2026, assembled from distributor-published reproductions of the ASTM B209 plate thickness table. ASTM B209 is the governing document. Confirm the row against a current copy of ASTM B209 or ASTM B209M before using these numbers to accept or reject material. Cast tool and jig plate and precision ground plate figures are product specifications, not consensus standard values.
Plus and minus in inches, applied to 6061, 7075 and 7050 rolled plate. The band widens with both thickness and width. A 1 inch nominal plate at 60 inches wide is entitled to a 0.104 inch total spread, which is more than a tenth of the thickness you ordered.
| Nominal thickness (in) | Width up to 48 in | Over 48 to 60 in | Over 60 to 72 in |
|---|---|---|---|
| 0.250 to 0.374 | ±0.014 | ±0.018 | ±0.022 |
| 0.375 to 0.499 | ±0.016 | ±0.021 | ±0.025 |
| 0.500 to 0.624 | ±0.018 | ±0.023 | ±0.028 |
| 0.625 to 0.874 | ±0.023 | ±0.029 | ±0.035 |
| 0.875 to 1.124 | ±0.035 | ±0.045 | ±0.052 |
| 1.125 to 1.499 | ±0.040 | ±0.050 | ±0.058 |
| 1.500 to 2.000 | ±0.045 | ±0.058 | ±0.068 |
| 2.001 to 3.000 | ±0.060 | ±0.075 | ±0.088 |
| 3.001 to 4.000 | ±0.075 | ±0.092 | ±0.105 |
| 4.001 to 6.000 | ±0.095 | ±0.115 | ±0.130 |
Below 0.250 inch the material is sheet, not plate, and a different and tighter ASTM B209 table applies. 5083 and 5052 are non heat-treatable and sit in a separate column that is close to this one but not identical. Confirm the row against a current copy of ASTM B209 or ASTM B209M before using it to accept or reject material.
The spec column is the full symmetric band. The observed column is where rolled plate lands in practice, which is the upper half of the band, because undersize plate gets remelted and oversize plate gets invoiced.
| Nominal (in) | Width band | Allowed by spec (in) | Typically arrives (in) |
|---|---|---|---|
| 0.250 | Up to 48 in | 0.236 to 0.264 | 0.254 to 0.263 |
| 0.375 | Up to 48 in | 0.359 to 0.391 | 0.380 to 0.389 |
| 0.500 | Up to 48 in | 0.482 to 0.518 | 0.505 to 0.520 |
| 0.750 | Up to 48 in | 0.727 to 0.773 | 0.757 to 0.771 |
| 1.000 | Over 48 to 60 in | 0.955 to 1.045 | 1.035 to 1.045 |
| 1.500 | Up to 48 in | 1.455 to 1.545 | 1.514 to 1.541 |
| 2.000 | Up to 48 in | 1.955 to 2.045 | 2.020 to 2.045 |
| 3.000 | Up to 48 in | 2.940 to 3.060 | 3.018 to 3.054 |
| 4.000 | Up to 48 in | 3.925 to 4.075 | 4.023 to 4.068 |
| Alloy | Product form | Thickness tolerance basis | Density (lb/in3) | Note |
|---|---|---|---|---|
| 6061-T651 | Rolled plate | ASTM B209 heat-treatable grid | 0.0975 | Workhorse plate. 0.500 nominal runs plus or minus 0.018 at 48 in wide. |
| 7075-T651 | Rolled plate | ASTM B209 heat-treatable grid | 0.1010 | Same tolerance band as 6061, higher strength, more residual stress on release. |
| 7075-T7351 | Rolled plate | ASTM B209 heat-treatable grid | 0.1010 | Overaged, lower residual stress, still the same thickness band. |
| 7050-T7451 | Rolled plate | AMS 4050 plate, B209 style thickness grid | 0.1020 | Thick section aerospace plate. Bands get wide above 3 in. |
| 5083-H321 | Rolled plate | ASTM B209 non heat-treatable column | 0.0960 | Marine plate. Close to the heat-treatable grid but a separate table. |
| 5052-H32 | Rolled plate | ASTM B209 non heat-treatable column | 0.0968 | Mostly sheet gauges. Plate table starts at 0.250 in. |
| 5000 series cast tool and jig plate | Cast, machined both faces | Supplier product spec | 0.0980 | Plus or minus 0.005 in flat, 0.250 to 4.000 in, no width dependence. |
| 6061 precision ground plate | Rolled then ground | Supplier product spec | 0.0975 | Plus or minus 0.003 in through 1.000 in nominal, plus or minus 0.005 in above. |
T_max = T_nom + tol
T_min = T_nom - tol
The tolerance is read from the table by nominal thickness and width band. Anything between T_min and T_max is conforming material and cannot be rejected on thickness.
observed range = T_nom + 0.3 x tol to T_nom + 0.9 x tol
This is not in the standard. It is the observed bias in rolled plate and it is the range you should plan your buy around.
C = skim + flatness allowance + relief allowance
skim = 0.010 for a light skim, 0.020 for flatten then finish
flatness allowance = bow per foot x blank length in feet / 2
relief allowance = 0.010 when a stress relief skim is taken, otherwise 0
With no blank length entered the flatness allowance falls back to a flat 0.010 inch per face.
N = 2 for both faces, 1 for a single face
margin = T_min - N x C - T_finished
A positive margin means the worst plate the mill is allowed to ship still cleans up. A negative margin means you are gambling on the mill running high, which it usually does, right up until the day it does not.
first N_std where (N_std - tol at N_std) - N x C - T_finished >= 0
The standard nominal list walked is 0.125, 0.190, 0.250, 0.3125, 0.375, 0.500, 0.625, 0.750, 0.875, 1.000, 1.125, 1.250, 1.500, 1.750, 2.000, 2.250, 2.500, 3.000, 3.500, 4.000, 4.500, 5.000 and 6.000 inches.
extra per face = (N_std - T_nom) / 2
purchased weight increase = 100 x (N_std - T_nom) / T_nom
increase in material machined away = 100 x (N_std - T_finished) / (T_nom - T_finished) - 100
plate weight = length x width x N_std x density
milled, free state = 0.0010 x span / 12
ground, free state = 0.0005 x span / 12
If the print calls for tighter than the milled figure over the part span, the operation is a grind, not a mill, and it needs to be quoted that way.
Need the stock to cut these from, get an instant quote on 6061, 7075 and 7050 plate cut to your blank size, with the mill cert on every piece so the as-received thickness is traceable back to the heat lot.
Usually not. Half inch nominal 6061 plate is allowed roughly plus or minus 0.018 inch under ASTM B209 at widths up to 48 inches, and mills deliberately run the high side of the band because undersize plate gets rejected and remelted while oversize plate ships and gets paid for. In practice 0.500 nominal arrives between 0.505 and 0.520 inch. Order 0.625 nominal if you need a finished 0.500 with clean faces.
Roughly plus or minus 0.035 inch at widths up to 48 inches, plus or minus 0.045 inch over 48 to 60 inches, and plus or minus 0.052 inch over 60 to 72 inches, for heat-treatable alloys such as 6061, 7075 and 7050. The tolerance is symmetric on paper but not in practice. A 1 inch nominal plate in 48 to 60 inch width commonly measures 1.035 to 1.045 inch, so plan your allowance off the high end.
Leave 0.010 to 0.020 inch per face for cleanup, plus a flatness allowance, plus 0.010 inch per face if you are taking a stress relief skim, then step up to the next standard nominal that survives the worst-case minus tolerance. For a 0.500 inch finished part in 6061-T651 that means ordering 0.625 nominal. For a 2.500 inch finished part held to a thousandth, order 2.750 or 3.000, not 2.500.
Because the economics only run one direction. Undersize plate fails incoming inspection, gets rejected and goes back to the melt, so the mill loses the whole roll. Oversize plate is inside the tolerance band, ships normally, and is invoiced by weight, so the mill gets paid for the extra metal. The result is that plate is consistently biased toward the top of the ASTM B209 band rather than centered on nominal.
Plus or minus 0.005 inch on every thickness from 0.250 to 4.000 inches, with no width dependence, because 5000 series cast tool and jig plate is machined on both faces after casting rather than rolled to size. That is roughly one seventh of the band you get on 1 inch rolled 6061. It is the reason fixture plates get bought as cast tool plate even though it costs more per pound and has about half the tensile strength.
No, not if the part tolerance is tighter than the mill tolerance. A 2.500 inch part held to plus or minus 0.001 inch cannot come out of 2.500 nominal plate, because the plate is entitled to arrive anywhere from about 2.440 to 2.560. Order the next nominal up and machine both faces. Ordering on-size only works when your part tolerance is looser than the ASTM B209 band for that thickness and width.