RFQ PREPARATION / CNC MACHINING INSIGHTS
“Aluminum” or “stainless steel” is often not enough information for a drawing-defined CNC order. A material callout should identify the grade the design requires, the condition if relevant, and whether an alternative needs buyer approval before machining begins.
State the exact alloy or grade
Use the material designation intended by the design rather than a broad material family. This allows the manufacturing review to compare the drawing requirement with the part’s function, machining approach and specified finishing. ExactMach has hands-on experience machining 6061 and 7075 aluminum grades; the drawing should still identify which grade the order requires.
Where the project references a material standard, include the designation and revision as part of the controlled document set. ASTM maintains the relevant standards ecosystem for many engineering materials; its official standards site is a useful source when a specific standard is required by the project.
Add condition and permitted alternatives when needed
Some designs need more than an alloy name. If the condition, temper, stock form, certification record, or an approved alternative matters to the assembly, state it clearly in the drawing or RFQ. If it does not matter, avoid adding restrictions that are not tied to a functional need.
| RFQ item | What to state |
|---|---|
| Material designation | The intended alloy or grade, not only the broad material family. |
| Condition or temper | Include it when it is specified by the design or a related standard. |
| Approved alternatives | Say whether substitution needs written buyer approval before machining. |
| Finish or heat treatment | Place it in the same RFQ package as the material callout. |
| Documentation request | Identify any record needed before the order is released. |
Link material to function, not just availability
Material selection can be driven by weight, corrosion environment, stiffness, thermal behavior, appearance, assembly fit or another design requirement. A one-line functional note is helpful when it explains why a material choice cannot change. It is more useful than asking the machining team to infer the reason from a part image.
For aluminum selection, compare 6061 and 7075 for CNC parts. If the project is evaluating other material families, see our guide to stainless steel versus titanium CNC parts.
Plan material and surface treatment together
Surface finish and heat treatment are part of the material decision, not separate afterthoughts. Put anodizing, heat treatment, cosmetic finish, masking, or other post-machining requirements in the RFQ at the same time as the material callout. This supports a clearer review of threaded features, mating surfaces and visible faces.
Do not bury the callout in an email
Place the final material requirement on the released PDF drawing or a named specification that accompanies it. Use the same revision identifier across the drawing, model and RFQ. If a material change is proposed after quotation, record the updated revision and the buyer approval rather than relying on an unclear filename.
Keep the request precise and practical
Clear material information reduces unnecessary assumptions, while still leaving room for a manufacturing question when the drawing is incomplete. ExactMach coordinates CNC milling, CNC turning, prototypes and custom parts around Shenzhen and Dongguan, including anodizing and heat-treatment support for drawing-defined international orders.