6061-T6511 Flat Bar: Sizes, Weights, Tolerances, and How to Order It
By Glorfindel
6061-T6511 flat bar is extruded rectangular aluminum bar supplied to ASTM B221, stress relieved by stretching so it holds shape when machined, with minimum properties of 38,000 psi ultimate tensile and 35,000 psi yield. To get its weight per foot, multiply thickness by width in inches by 1.17. This post gives the full size and weight tables, the mechanical minimums, the tolerance realities that surprise people who expect bar to arrive flat and square, and the one substitution worth knowing when the section you want is not stocked.
In Short
- →6061-T6511 flat bar, also sold as rectangular bar, is extruded, stretched for stress relief, aged, and lightly straightened. Specification is ASTM B221.
- →Weight per foot is thickness x width x 1.17 for 6061 at 0.0975 lb per cubic inch. Distributor tables using 0.098 run about half a percent heavier.
- →Minimum mechanical properties are 38,000 psi ultimate and 35,000 psi yield with 17 percent elongation, the same as extruded round bar.
- →Extruded flat bar carries mill-finish surfaces and commercial straightness and twist. If you need a flat, square, dimensionally tight blank, plate cut to size is usually the better buy.
- →Standard mill stock length is 12 feet. Order the length you need.
- →If the size you want is not a stocked bar section, the same rectangle cut from plate weighs exactly the same and is often available faster.
Weight Per Foot by Section
Thickness down the left, width across the top, pounds per lineal foot. Computed as thickness x width x 12 x 0.0975.
| Thickness (in) | 1 in | 2 in | 3 in | 4 in | 6 in |
|---|---|---|---|---|---|
| 0.125 | 0.146 | 0.293 | 0.439 | 0.585 | 0.878 |
| 0.250 | 0.293 | 0.585 | 0.878 | 1.170 | 1.755 |
| 0.375 | 0.439 | 0.878 | 1.316 | 1.755 | 2.633 |
| 0.500 | 0.585 | 1.170 | 1.755 | 2.340 | 3.510 |
| 0.750 | 0.878 | 1.755 | 2.633 | 3.510 | 5.265 |
| 1.000 | 1.170 | 2.340 | 3.510 | 4.680 | 7.020 |
| 1.500 | - | 3.510 | 5.265 | 7.020 | 10.530 |
| 2.000 | - | 4.680 | 7.020 | 9.360 | 14.040 |
Mechanical Minimums
Identical to extruded round bar, because it is the same process and the same temper.
| Product | Alloy and temper | Min ultimate | Min yield | Elongation |
|---|---|---|---|---|
| Extruded flat bar | 6061-T6511 | 38,000 psi | 35,000 psi | 17 percent |
| Cold finished bar | 6061-T651 | 42,000 psi | 35,000 psi | 17 percent |
| Rolled plate | 6061-T651 | 42,000 psi | 35,000 psi | varies by thickness |
What Extruded Flat Bar Is Not
This is the expectation gap that generates most of the complaints about bar stock, and it is worth being blunt about.
- It is not precision ground. Extruded bar arrives with mill-finish surfaces and commercial dimensional tolerances, not a machined finish.
- It is not guaranteed flat or square. Commercial extruded product carries allowances for straightness, twist, and flatness set by the Aluminum Association, and a long thin section can use a lot of that allowance.
- It is not a finished blank. If you need four square sides and a controlled thickness, you are machining it, so buy with facing stock in mind.
- Precision or manifold-quality extruded bar exists for exactly this reason. It holds roughly half the commercial twist and straightness allowance, tightens the dimensional tolerance to the plus side, and carries an elevated minimum ultimate around 44 ksi. It costs more and it is the right call for hydraulic manifolds and fixture bodies.
When to Buy Plate Instead
The most useful thing we can tell a buyer about flat bar is when not to buy it.
- Your section is not a stocked bar size. A rectangle cut from plate weighs exactly the same and we can cut any dimension, so you are not forced up to the next catalogue size.
- You need dimensional control. Plate is rolled to tighter thickness tolerance than extruded bar is extruded to, and 6061-T651 plate carries the higher 42,000 psi ultimate minimum.
- You need width beyond stocked bar. Plate goes far wider than bar sections do.
- You need thick and short rather than thin and long. Buying a 3 inch thick, 8 inch wide piece is a plate purchase, not a bar purchase.
- Buy bar when the section is standard, the length is long, and the mill finish is acceptable. That is a real and common case, and bar is cheaper there.
What to Put on the Purchase Order
- 6061-T6511, ASTM B221, with AMS-QQ-A-200/8 added if your print uses the legacy callout.
- Thickness x width x the length you need, not the 12 foot stock length.
- Certification requirement. Mill certs with heat number and lot traceability ship on every order from us, with DFARS and domestic-melt options.
- Straightness and twist, if the part is long. Ask for the number in writing rather than assuming commercial is good enough.
- Whether precision or manifold quality is required, if flatness and twist actually drive the part.
6061-T6511 flat bar is extruded, stress relieved, and supplied to ASTM B221 with a 38,000 psi ultimate minimum and a 35,000 psi yield. Use thickness x width x 1.17 to get pounds per foot, buy the length you need rather than a 12 foot stick, and remember that if the section is not stocked, the identical rectangle cut from plate weighs the same and is frequently the better purchase.
Frequently Asked Questions
How much does 6061-T6511 flat bar weigh per foot?
Multiply thickness by width in inches by 1.17. A 1 x 4 inch bar is 4.68 pounds per foot and a 0.5 x 2 inch bar is 1.17. Distributor tables using a density of 0.098 rather than 0.0975 will read about half a percent heavier.
Is 6061-T6511 flat bar the same as 6061-T6 flat bar?
T6511 is T6 that has additionally been stress relieved by stretching and lightly straightened. Mechanical minimums are the same, but the stress relief matters if you are machining the bar, because unrelieved material moves when you remove metal from one side.
What is the difference between flat bar and rectangular bar?
Nothing. They are two names for the same extruded rectangular section. Some catalogues split them by size, calling narrow sections flat bar and wider or thicker ones rectangular bar, but the product and the specification are identical.
Is aluminum flat bar flat?
Not to a machined standard. Commercial extruded bar carries Aluminum Association allowances for straightness, twist and flatness, and a long thin section can use a lot of that allowance. If flatness drives your part, specify precision or manifold quality, or buy plate cut to size.
Can I get flat bar in a size that is not standard?
Yes, by cutting it from plate. A rectangle cut from 6061-T651 plate weighs exactly the same as bar of identical dimensions and can be any thickness and width we stock, which is 0.25 to 10 inches thick. It also carries the higher 42,000 psi ultimate minimum.
6061-T6511 flat bar
Price flat bar, or the same rectangle from plate.
Tell us the section and length. We will price extruded bar and a plate-cut equivalent, with mill certs and a committed ship date on either.