Machining Decision Matrix
| Buyer question | 6061 | 7075 |
|---|---|---|
| Why select it? | Balanced strength, corrosion resistance, fabrication and cost | Higher strength and fatigue performance where design requires it |
| Machining behavior | Generally predictable in common T6/T651 product forms | Machines well, but high-strength thin or heavily pocketed parts still need distortion control |
| Welding | Commonly weldable with a qualified procedure; properties near the weld must be considered | Generally not the preferred fusion-welded structural alloy |
| Corrosion / finish | Usually better general corrosion resistance; widely anodized | Often needs more deliberate corrosion protection and finish validation |
| Cost driver | Material is usually less expensive; simpler process chain in many projects | Higher stock cost plus possible finishing, inspection and scrap-risk costs |
Distortion Matters More Than Cutting Speed
A plate can machine cleanly and still move after deep pockets are opened. Specify product form and temper, keep machining allowance balanced where possible, use an appropriate roughing/finishing sequence and verify final flatness after the part reaches a stable condition. T651-type stress-relieved plate is often considered for machined plate work, but the exact designation and availability must be confirmed for the ordered product.
Tooling, Chips and Surface Finish
- Use sharp tools and geometry suitable for non-ferrous metals.
- Control chip evacuation so recutting does not damage the surface.
- Validate lubricant or coolant compatibility with the alloy and subsequent finishing process.
- Treat thin walls, ribs and interrupted cuts as stability problems, not only speed-and-feed problems.
- Define finish acceptance with a measurable requirement rather than “good surface.”
Cost Comparison Should Include the Whole Part
A fair quotation includes raw stock size, material yield, machining time, scrap risk, heat-treatment condition, surface treatment, inspection and documentation. Choosing 7075 for an unspecified “strength upgrade” can increase cost without improving a part whose governing limit is stiffness, corrosion, joint design or geometry.
Questions to Put on the RFQ
- Alloy, temper and product form
- Stock thickness and machining allowance
- Final drawing dimensions, flatness and surface finish
- Welding, anodizing or coating requirements
- Critical characteristics and inspection method
- Required material certificate and traceability
- Whether substitutions or alternate tempers may be quoted
Compare 6061 and 7075 against the drawing and service conditions rather than selecting by strength alone.
Post time: Jun-05-2026