Tolerances

TOOL STEEL TOLERANCES

Length of bars

Standard Tool Steel mill lengths are 8-12 foot - random. Sizes 4-1/2" diameter or equivalent cross section and larger are 7-12 foot - random.

Size Tolerances

De-Carb Finish Round Bar
Size Over Tolerance
1/4" to under 1-1/2" diameter 0.010" +0.005"
1-1/2" to under 3-1/16" diameter 0.020" +0.015"
3-1/16" to under 4-1/16" diameter 0.040" +0.020"
4-1/16" to under 5" diameter 0.065" +0.020"
5" to under 7-1/16" diameter 0.084" +0.030"
7-1/16" to under 12-1/16" 0.105" +0.040"
12-1/16" and over 0.125" +0.040

De-Carb Finish flats and squares

Flats and squares are machined oversize on the thickness and width. All sizes have a thickness tolerance of +0.015"/0.035" over the normal size, - and a width tolerance according to the following table.

Plate Saw Cut Width Oversize tolerance Minus
Up to 2" wide +0.030" To 0.065" 0.000
Over 2" wide to 3-1/2" inclusive +0.030" To 0.125" 0.000
Over 3-1/2" to 5" inclusive +0.035" To 0.125" 0.000
Over 5" +0.035" To 0.188" 0.000

Machining Allowances

When ordering forgings or hot rolled bar stock allowance must be made in machining to remove all the decarburized surface.

De-Carb Finish tool steels have the appropriate amount of stock already removed.

ALLOY STEEL TOLERANCES

Length of Bars

Standard hot-rolled mill length bars are 16-24 foot-random, and certain grades and sizes are specified as having a 2 foot length in spread with 10% maximum short random lengths.

H. R. Round Bar Size - Tolerances

Variation from size, inches

Specified Sizes, Inches Over Under Out-of-Round of Square inches.
3/8" to 5/16" +0.005" -0.005" 0.008"
Over 5/16" to 7/16" +0.006" -0.006" 0.009"
Over 7/16" to 5/8" +0.007" -0.007" 0.010"
Over 5/8" to 7/8" +0.008" -0.008" 0.012"
Over 7/8" to 1" +0.009" -0.009" 0.013"
Over 1" to 1-1/8" +0.010" -0.010" 0.015"
Over 1-1/8" to 1-1/4" +0.011" -0.011" 0.016"
Over 1-1/4" to 1-3/8" +0.012" -0.012" 0.018"
Over 1-3/8" to 1-1/2" +0.014" -0.014 0.021"
Over 1-1/2" to 2" +1/64" -1/64" 0.023"
Over 2" to 2-1/2" +1/32" 0" 0.023"
Over 2-1/2" to 3-1/2" +3/64" 0" 0.35"
Over 3-1/2" to 4-1/2" +1/16" 0" 0.046"
Over 4-1/2" to 5-1/2" +5/64" 0" 0.058"
Over 5-1/2" to 6-1/2" +1/8" 0" 0.070"
Over 6-1/2" to 8-1/4" +5/32" 0" 0.085"
Over 8-1/4" to 9-1/2" +3/16" 0" 0.100"
Over 9-1/2" to 10" +1/4" 0" 0.120"

Out-of round is the difference between the maximum and minimum diameters of the bar, measured at the same cross section.

Machine Straightening - Bars are furnished with a permissible variation from a straight line not to exceed 1/8 inch in any 5 foot, but may not exceed 1/8 x Number of feet of length / 5

NOTE: 8620 Alloy Bars as rolled - not machine straightened.

Hot Rolled Alloy Plate - Tolerances

Variations of thickness Undersize Oversize
Over 1/2" to under 3/4" 0.010" 0.030"
3/4" to under 1" 0.010" 0.040"
1" to under 2" 0.010" 0.060"
2" to under 3" 0.010" 0.100"
3" to under 4" 0.010" 0.110"
4" to under 6" 0.010" 0.150"
6" to under 10" 0.010" 0.240"

MACHINING TOLERANCES

Allowances for Machining Bars

When regular quality alloy or special quality or carbon hot rolled steel bars are to be machined, experience has shown that it is advisable for the purchaser to make adequate allowances for surface finishing and specify hot rolled or thermally treated sizes accordingly. Such allowances require consideration for the manufacturing practice utilized to remove the surface metal, as well as the bar size, length, straightness, size tolerance, and out-of-round tolerance. Bars should be straightened before machining.

The accompanying table contains the recommended minimum machining allowance per side for steel bars.

Recommended Minimum Machining

Allowance per side

Percent of specified size

Bars Recommended Minimum Machining allowance per side percent of specified size Non-Resulfurized Resulfurized
Turned on Centers 3.0% 3.8%
Centerless Turned or Ground 2.6% 3.4%

Note 1 - Based on bars within special straightness tolerance.

Note 2 - Since straightness is a function of length, additional machining allowance may be required for turning on centers.

*Using this table, the following example can be made:

When machined by centerless turning or grinding, a 2" non-resulfurized hot rolled steel bar would require 0.052" (2" * 2.6% (.026)= 0.052") removal from the radius.

When regular quality alloy steel and special quality carbon steel hot rolled bars, such as squares and flats, are machined by methods other than shown in the table, the recommended minimum surface removal is 1.6% of the specified dimension for non-resulfurized steel. For sizes under 5/8 of an inch should be 0.010 of an inch for non-resulfurized steel and 0.015 of an inch for non-resulfurized steel.

Resulfurized grades are typified by a poorer surface and the increased surface removal shown above and in the table is recommended. Conversely, steels made to higher qualities may permit lesser amounts of surface removal depending on size, grade and quality specified.

STANDARD VARIATIONS IN CUTTING

Material Cut or Sawed from stock sizes

Standard variations for cutting have been established as listed below. All variations in sawing will be within these standards. If you need more accurate cutting, we will be glad to quote you on special requirements

Cutting Tolerances

Rounds and Squares up to 3" +0.0625" / -0.00"
Rounds and Squares 3" to 6" +0.125" / -0.00"
Rounds and Squares over 6" +0.1875" / -0.00"
Flats up to 3" wide +0.0625" / -0.00"
Flats over 3" to 10" wide +0.125" / -0.00"
Flats over 10" wide +0.1875 / -0.00"

Plate Sawed Material

Cut from various thicknessess of carbon and alloy plate.

Straightness Tolerances

Bars are furnished with a permissible variation from a straight line not to exceed 1/8" over each 5 feet of bar length.

Width Tolerances

Material Thickness CARBON and ALLOY STEELS
Up to 3-1/2" Thick +0.060" To +0.125"
Over 3-1/2" to under 5" +0.060" To +0.1875"
5" and Over +0.060 To +0.250

Note: This tolerance does not apply if material is cut narrower than plate thickness.