Cold rolled alloy steel sheet in the 0.018 in to 0.250 in nominal range is routinely produced to a thickness tolerance of +/-0.006 in at light gauges, expanding to roughly +/-0.010 in to +/-0.015 in once nominal thickness crosses about 0.130 in, per OnlineMetals tolerance tables for cold rolled sheet [S1][S5].
The governing reference for cold rolled sheet and plate in stainless and heat resisting steels is ASTM A480, which lists permissible variations under specified thickness from 0.005 in (0.13 mm) up through 3.250 in (82.6 mm) in 0.001 in to 0.014 in steps, with cold rolled coils in cut lengths and coils typically running to tolerances tighter than the published table [S3].
Where the +/-0.006 in band comes from, and when it widens
For OnlineMetals cold rolled sheet, the published width tolerance of +/-0.006 in is mirrored as the thickness tolerance on light gauges, with 1075 spring-tempered at 0.010 in nominal shown as a representative alloy [S1]. Protocase publishes the same number for cold rolled steel: 11 gauge, 0.120 in (3.05 mm) nominal, +/-0.006 in [S2].
Engineers Edge gauge tables step that band with width: at 0.018 to 0.028 in (0.46 to 0.71 mm) thickness, the tolerance is 0.002 in (0.051 mm) on 36 in (914.4 mm) stock and 0.0025 in (0.064 mm) on 48 in (1219 mm) stock; 0.029 to 0.036 in thickness runs 0.003 in and 0.004 in respectively on the same widths [S8]. Those tight numbers are why cold rolled sheet is the default starting stock for precision blanking and stamping, not hot rolled P&O.
OnlineMetals' alloy sheet table for 4130 normalized cold rolled at 0.160 in lists +/-0.009 in thickness tolerance, already past the 0.130 in transition where the band opens up [S5]. Komacut's July 2026 reference table shows the trend continuing: nominal 3.50 mm carries +/-0.10 mm to +/-0.15 mm, and nominal above 4.00 mm reaches +/-0.15 mm to +/-0.18 mm [S4].
ASTM A480 thickness table: the actual published numbers
ASTM A480 lists permissible thickness variations for cold rolled sheets in cut lengths and coils across stainless and heat resisting steels. Selected bands pulled directly from the O'Neal Steel reproduction: nominal 0.005 in to 0.007 in (0.13 to 0.18 mm) carries +/-0.001 in over and +/-0.003 in under; 0.016 in to 0.026 in (0.41 to 0.66 mm) runs +/-0.003 in over and +/-0.008 in under; 0.072 in to 0.084 in (1.83 to 2.11 mm) runs +/-0.007 in over and +/-0.018 in under; 0.130 in to 0.145 in (3.30 to 3.68 mm) runs +/-0.010 in over and +/-0.025 in under; 0.160 in to 0.170 in runs +/-0.014 in over and +/-0.036 in under; and 0.250 in and over falls under the plate table, not sheet [S3].
For plate up to 10 in (254 mm) inclusive, the tolerance under specified thickness is 0.010 in (0.25 mm), with width and length tolerances published separately in the same A480 table [S3]. The key A480 note: thickness measurements are taken at least 3/8 in (9.52 mm) from the longitudinal edge, which prevents the edge crown from inflating the read.
For European cold rolled wide stainless strip, BS EN 10259 covers thicknesses up to 6.5 mm rather than stopping at 3.0 mm, and the special tolerance range is about 70% of the normal range, giving procurement a tighter commercial option without changing the alloy or the mill [S6].
Comparison: tolerance bands across cold rolled sheet, alloy sheet, and plate
Putting the published numbers side by side clarifies which stock to order for a given tolerance budget. Cold rolled mild sheet at 0.120 in (11 ga) is +/-0.006 in per Protocase, while 4130 normalized cold rolled at 0.160 in is +/-0.009 in per OnlineMetals alloy tables, and ASTM A480 cold rolled sheet at 0.160 to 0.170 in is +/-0.014 in over and -0.036 in under [S2][S3][S5]. That gap is the practical reason the same part quoted in 1018 versus 4130 versus 304 stainless will land at three different thickness bands even at the same nominal.
The Komacut July 2026 table shows the same widening in metric: 3.50 mm nominal at +/-0.10 mm to +/-0.15 mm, while stock above 4.00 mm reaches +/-0.15 mm to +/-0.18 mm [S4]. EMJ's reference reproduces AISI flat bar data, where for carbon maximum 0.28% on a 2 in wide by 1 in thick flat, the width tolerance is 0.005 in and the thickness tolerance matches, giving a benchmark for cold drawn flats that share the same +/-0.005 in mill discipline as thin cold rolled sheet [S9].
For procurement decisions, the rule is simple: if the part needs under +/-0.005 in on thickness, plan to grind or machine the stock down; the mill will not hit it on as-rolled sheet. Verify incoming stock with a thickness gauge at 3/8 in inboard from the edge, matching the A480 measurement convention, and back the reading with a coating thickness gauge when surface treatment is applied downstream.
Flatness, width, and camber: the tolerances the thickness table hides
Rolled Alloys' flatness reference notes that on a longer dimension under 36 in, the flatness tolerance is 1/4 in, and tighter flatness is conditional on minimum specified yield strength, since higher yield stock springs back more off the leveler [S7]. The A480 width table for hot rolled and cold rolled sheets (not resquared) sets 0 over and 1/16 in under for stock 24 to under 48 in wide, and 0 over and 1/8 in under for stock 48 in to 60 in wide inclusive, with all-thicknesses coverage [S3].
For stainless sheared mill plate, A480 length tolerances over 108 in wide step from 1-1/4 in over and 7/8 in under at the 0 to under 3/8 in thickness band, up to 1-1/8 in over and 1 in under at the 3 in to under 4 in thickness band, on the over-240 in length column [S3]. Those are the numbers that catch engineers out when they assume a "tolerance on thickness" implicitly means a tight tolerance on length and width as well; it does not.
Selecting the right stock for the tolerance you actually need
For a 0.060 in nominal cold rolled part where +/-0.005 in on thickness is the design budget, the published mill tolerance of roughly +/-0.002 in to +/-0.004 in at that gauge covers the requirement with margin, so 1008 or 1018 cold rolled sheet is the cost-effective pick, not alloy [S1][S8]. If the part also needs through-hardening or better fatigue life, 4130 normalized cold rolled at the same nominal steps the tolerance out to roughly +/-0.005 in to +/-0.009 in depending on gauge, and is still inside a +/-0.010 in budget [S5].
For corrosion or temperature service where 304/316 stainless is the alloy of choice, BS EN 10259 should be cited on the print with the "special" tolerance range selected, which is about 70% of the normal range, since that is the contractual path to a tighter thickness band on European mill stock rather than a domestic A480 coil [S6]. On the incoming inspection side, the same ultrasonic thickness gauge used for wall-thickness verification on plate and tubing applies to thin cold rolled sheet when calibrated for the lower mass and the couplant used is the water-gel type rather than the high-viscosity paste used on heavy plate.
Procurement should refuse A480 coil stock for any print that calls out flatness tighter than 1/4 in on a dimension under 36 in, since that limit is the flatness baseline for sheet and plate and tighter demands a stretcher-leveled or precision-ground variant, which is a different product line at a different price.
Failure modes and constraints engineers miss
Three recurring traps show up on cold rolled alloy sheet orders. First, ASTM A480 tolerances are asymmetrical (more under than over) on cold rolled sheet, so a print that reads "0.060 in +/-0.005 in" can be rejected by a mill that ships 0.055 in and is inside A480 but outside the symmetric drawing callout; the fix is to either accept A480's asymmetric band or specify A480 special tolerances in the note block [S3].
Second, online tolerance tables from service centers are seller-applied bands, not A480 bands, and OnlineMetals explicitly states a cut tolerance of +0.125 in, -0 in on long and sheet products unless specified otherwise, which sits on top of the mill thickness tolerance and matters for cut-to-length blanks, not coils [S5]. Third, switching from a 1008/1018 cold rolled sheet to a 4130 normalized sheet at the same nominal can quietly widen the thickness band by 50% or more, because 4130 is sold against alloy sheet tables, not mild sheet tables, and the difference lands in tolerance stack-up at the press, not in the BOM [S1][S5].
For molds, dies, and large base plates that will be machined on both faces, the upstream stock tolerance matters less because material will be removed; for stamped or roll-formed parts that ship as-rolled, the as-shipped thickness band is the part thickness band, and it deserves the same metrology discipline as a finished dimension. Engineers should cross-reference the comparable spec-anchored analysis of 1.2738 vs P20 for large mold base plates when the alloy choice itself is the decision variable, since the same tolerance-versus-alloy trade-off recurs across mold and die work.
Track these signals on the next quote cycle: confirm whether the mill cites ASTM A480, AISI, or a house standard on the MTR, since that determines which tolerance table is contractually binding; flag any 4130/4140/4340 cold rolled sheet order where the requested gauge is under 0.060 in, because that crosses into the tighter cold rolled sheet band where alloy-specific tables diverge from mild sheet tables by up to +/-0.005 in; and request the special tolerance range under BS EN 10259 when sourcing European cold rolled stainless, since the 30% tighter band is often available at no premium over the normal range [S3][S5][S6].