Guide
What should you know before specifying aluminum stamping in 6061-T6?
Aluminum stamping is the process of blanking, piercing and forming brackets, clips and covers from aluminum sheet or strip on a die, most often in 6061-T6 on a die shop’s own floor. The alloy and its temper decide how tightly the part can bend, how far it springs back and how the die itself has to be built, so a drawing written the way a steel stamping is written often needs a second look before it is quoted.
By Saola Manufacturing engineering team · Published · Updated
Most of what makes an aluminum stamping different from a steel one traces back to two facts: aluminum alloys split into heat-treatable and non-heat-treatable families that behave differently under a punch, and aluminum reacts with tool steel differently than steel or brass does. This guide works through temper, bend radius, springback, burrs, hole spacing, galling, die choice and finishing in that order, so a drawing for a bracket, clip or cover can be written once instead of clarified twice.
On this page
Why does temper matter when you specify aluminum for a stamped part?
6061 is a heat-treatable alloy that reaches its strength through solution heat treatment and aging, while 5052 is a non-heat-treatable alloy that reaches its strength through cold work; the softer the starting condition, the more easily the sheet forms in the die.
The split is written into the material specification itself. ASTM B209/B209M, the specification for aluminum and aluminum-alloy sheet and plate, separates heat-treatable alloys from non-heat-treatable alloys in its own scope, because the two families are supplied, formed and finished on different logic. 6061 and 5052 are both wrought alloys carried in the Aluminum Association’s alloy register: 6061 takes a T-temper from heat treatment, and 5052 takes an H-temper from strain hardening instead, since it has no age-hardening response to speak of.
That difference shows up at the press. A bracket blanked and formed in 6061-O or 6061-T4, then solution heat-treated and aged to T6 afterward, forms more like the annealed alloy it started as. The same bracket ordered as 6061-T6 stock and formed cold has to work with the fully aged material’s resistance to bending, which is why the temper at the moment of forming matters as much as the temper on the certificate. State which sequence the drawing assumes; if a project needs an alloy or temper outside 6061-T6, ask in the RFQ rather than assume it is on the shelf, since stocked material is 6061-T6 aluminum sheet alongside brass strip and steel to drawing specification.
What minimum bend radius should an aluminum stamping drawing call out?
Minimum bend radius depends on alloy, temper and sheet thickness together, and it grows sharply as the temper gets harder; published aircraft sheet-forming guidance shows 6061-T6 needing several times the radius that annealed 6061 or 5052 needs at the same thickness.
| Alloy and temper | 0.032 in sheet | 0.064 in sheet | 0.128 in sheet |
|---|---|---|---|
| 5052-O | Flat, no radius | 0 to 1t | 0 to 1t |
| 5052-H32 | Flat, no radius | 0.5t to 1t | 0.5t to 1.5t |
| 6061-O | 0 to 1t | 0 to 1t | 0 to 1t |
| 6061-T4 | 0 to 1t | 0.5t to 1.5t | 1t to 2t |
| 6061-T6 | 0.5t to 1.5t | 1t to 2t | 1.5t to 3t |
Two rows above make the point without needing to read every column. At the same thickness, 5052 and annealed or T4 6061 can often take a flat or near-flat bend where fully aged 6061-T6 already needs a measurable radius, and the gap widens as the sheet gets thicker. A drawing that specifies 6061-T6 and a radius sized for 5052 is asking the die to do something the alloy will not do without cracking at the outer fiber of the bend.
Grain direction changes the picture again. The same guidance notes that a bend line set at an angle to the rolling direction of the sheet, ideally 90 degrees across the grain, tolerates a tighter radius than a bend line running parallel to the grain, because the fibers being stretched on the outside of the bend lie across the fold instead of along it. When the strip layout allows it, orient bend lines across the grain during nesting; where a bend has to run with the grain, budget the larger radius instead of fighting the material. As with any formed feature, give the inside radius as a reference or a range on the drawing and let the die designer choose within it, rather than holding it to a tight tolerance no die can guarantee.
How much should you plan for springback in a stamped aluminum bracket?
Springback grows with the material’s resistance to bending relative to its stiffness, so a bracket in 6061-T6 springs back more after the punch releases than the same shape in 5052 or in 6061-O or -T4, and it grows further as the bend approaches the alloy’s minimum radius.
A die built from a flat drawing angle produces a part that opens up slightly once it leaves the tool, because the metal that was elastically stressed relaxes back. The usual fix is to overbend the punch angle so the part relaxes to the angle actually wanted, or to bottom the punch into the material at the end of the stroke so it locally yields and sets the angle rather than only elastically flexing it. Which approach fits depends on the die design, not the drawing, so the drawing should state the finished angle and its tolerance and leave the compensation to the die maker.
Springback is also a reason to treat a temper swap as a real change rather than a substitution. Forming the same geometry in 6061-T6 instead of the 6061-T4 the die was tuned for changes both the minimum radius and the amount of springback, so a die proven on one temper cannot be assumed to hold the same angle on another without a trial. Flag any temper change in writing before it reaches the press.
How should burr side and burr height be specified on an aluminum stamping drawing?
Give a maximum burr height and state which face of the part the burr may be on; a note that reads only “remove all burrs” cannot be inspected, and that is true for aluminum exactly as it is for steel or brass.
The mechanics are the same shearing action described for any punched material: a smooth, burnished band on the punch side, a rougher fracture band further through the thickness, and a burr pushed out on the die side as the slug separates. Aluminum is softer than steel, so the burr on a given die tends to be smaller for the same clearance and edge condition, but it is not absent, and it still grows as the punch and die edges wear. State the maximum height and the allowed side rather than leaving the die’s current wear state to decide it.
Burr direction matters for the same reason it does anywhere else: a part that slides against another component, seats a gasket, or is handled by people should have the burr on the side facing away from contact. Where a coating follows stamping, remember that anodizing and plating both build up on edges as well as faces, so a burr limit and an edge-break note set before finishing can read differently once the finish is on. The surface finishing page covers deburring alongside the finishes that follow it.
What hole-to-edge and hole-to-bend spacing keeps an aluminum stamped part manufacturable?
Hole-to-edge and hole-to-hole spacing should be at least one material thickness on an aluminum stamping, the same baseline used for brass and steel; a hole punched closer than that tears the web instead of shearing it cleanly, and a hole placed too near a bend line moves as the flange stretches and springs back.
This is the rule the die shop already applies to every material it runs, because it comes from how a punch shears a web rather than from the alloy: closer spacing than one thickness leaves too little material to resist tearing before the slug separates. Softer tempers such as 6061-O or 5052 are more forgiving of a tight edge distance than fully aged 6061-T6, but designing to the same one-thickness minimum across tempers keeps a part reusable if the temper changes later in the project.
Holes that cross a bend line carry the extra variation described in the bend-radius and springback sections above: the bend location, the springback and the sheet thickness all feed into where that hole ends up relative to the rest of the part. For a hole that only clears a fastener, a wider position tolerance or a slot absorbs the variation cheaply. For a hole that has to align tightly with a feature on another flat, say so in the RFQ; piercing it after forming is a different die design and a different cost, and it is easier to price correctly when it is called out up front rather than found at first inspection. The stamping capability page lists this rule alongside the other design choices that drive die cost.
Why does aluminum gall in a stamping die, and how is it controlled?
Aluminum tends to smear and cold-weld onto tool steel under the pressure of blanking and forming more readily than steel or brass does, so die clearance, punch surface finish and lubrication matter more on an aluminum job than on the same die run in a harder material.
Galling starts when the thin oxide layer on the aluminum surface breaks down under contact pressure and the exposed metal transfers onto the punch or die face. Once a high spot of transferred aluminum builds up on the tool, it scores every part that follows, degrades hole and edge quality, and raises the force the press has to deliver. Because it is progressive, a die that ran clean on the first shift can be scoring parts by the last one if nothing is done between runs.
The controls are mostly about matching the tool to the material rather than the drawing: die clearance set for the specific alloy and temper being run, a polished or hard-coated punch and die face on tooling dedicated to aluminum, and a stamping lubricant chosen for aluminum rather than reused from a steel job on the same press. None of this shows up on the part drawing, but a drawing that calls out alloy and temper precisely gives the die shop what it needs to set clearance and lubrication correctly before the first strip runs.
Should an aluminum bracket run on a progressive die or a compound die?
A compound die cuts the outline and pierces holes in the same stroke and suits a simple flat aluminum part; a progressive die feeds strip through a row of stations that pierce, form and cut off, and suits a bracket that needs one or more bends, because the part leaves the press already formed.
Both die types are set and run on the die shop’s own floor, on brass strip, 6061-T6 aluminum sheet and steel to drawing specification alike. The choice between them follows the part geometry more than the material: a flat washer or plate with a hole pattern is a compound-die candidate regardless of alloy, while a bracket with a bend, a coined feature, or several pierced holes at different stations is a progressive-die candidate because each operation becomes its own station in the strip.
Strip layout is decided at this stage too, and it is where the grain-direction choice from the bend-radius section gets locked in: nesting the part so its bend lines fall across the rolling direction of the coil, where the outline allows it, buys back some of the margin that a hard temper like 6061-T6 otherwise spends. If lifetime volume is still uncertain and a die has not been committed to yet, a separate guide works through when a die is worth building at all against cutting the same part from flat sheet.
What finish should you specify for a stamped aluminum part?
Anodizing is the finish built for aluminum and follows stamping, applied by a partner plant we manage; zinc plating is a finish for iron and steel and is not applied to aluminum parts, so the base metal decides which one belongs on the drawing, not habit carried over from a steel part.
| Step | Governing document | Base metal in its scope |
|---|---|---|
| Sheet material certification | ASTM B209/B209M-21a | Aluminum and aluminum alloys, heat-treatable and non-heat-treatable |
| Anodizing | MIL-A-8625F | Aluminum and aluminum alloys |
| Zinc plating | ASTM B633-23 | Iron and steel; does not cover aluminum |
Anodizing on aluminum and powder coating are applied by partner plants we manage, and the quote names where each step is done; zinc plating, RoHS-compliant blue trivalent chromate and oil-dip rust protection are the finishes offered for steel parts. State on the drawing whether an aluminum part is anodized in the temper it was formed in or after a later heat treatment to T6, since that changes the finishing sequence, not just the color or thickness of the coating. A guide to anodizing vs powder coating vs zinc plating compares the three finishes and where each applies. If the assembly mixes an anodized aluminum bracket with zinc-plated steel fasteners, note the pairing in the RFQ so dissimilar-metal contact is a decision made on purpose rather than discovered later.
Frequently asked
Can an aluminum alloy or temper other than 6061-T6 be stamped?
Ask in the RFQ. 6061-T6 aluminum sheet is run routinely alongside brass strip and steel to drawing specification, but a different alloy or temper needs to be discussed and priced before it is quoted, rather than assumed to be on the shelf.
Does bending across the grain remove the need for a bend radius?
No. Bending across the grain allows a tighter radius than bending with it, but the radius still depends on alloy, temper and thickness, as the bend-radius table above shows. Grain direction narrows the margin needed; it does not remove it.
Should the bend radius carry a tight tolerance on the drawing?
Usually no. Give the inside radius as a reference or a range and control the features the bend positions instead, the same practice used on any stamped part regardless of material.
Is a stamped aluminum bracket anodized before or after forming?
Either can work, but the drawing should say which. Anodizing after forming and any post-form heat treatment is the more common sequence; state the intended temper at the time of anodizing so the finishing schedule matches the part.
Why would the same bracket need a different die in aluminum than in steel?
Die clearance, punch finish and lubrication are set for the specific alloy and temper being run, because aluminum galls against tool steel more readily than steel does against itself. Tooling proven on a steel version of a part is not assumed to run aluminum cleanly without that setup.
Sources
- AC 43.13-1B, Acceptable Methods, Techniques, and Practices: Aircraft Inspection and Repair, with Change 1, Table 4-6 and Section 4-55 (bend radius and grain direction), Federal Aviation Administration, 1998 (Change 1, 2001)
- ASTM B209/B209M-21a, Standard Specification for Aluminum and Aluminum-Alloy Sheet and Plate, scope, ASTM International, 2021
- MIL-A-8625F, Anodic Coatings for Aluminum and Aluminum Alloys, Department of Defense, 1993
- ASTM B633-23, Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel, scope, ASTM International, 2023
- International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys (Teal Sheets), The Aluminum Association, accessed September 2026