I run quotes for a machining shop in Bao'an, Shenzhen. Aluminum housings and bulk turned parts are maybe 60% of what goes out of our door. When a buyer comes to us for volume aluminum work, the conversation almost always follows the same track — and the buyers who ask the uncomfortable questions early are the ones whose projects don't blow up halfway.
Here's what actually gets checked, from the supplier's side of the table.
1. Which "aluminum" do you mean?
6061-T6, 6063 extrusion, ADC12 die-cast blanks and 5052 sheet all machine differently and price differently. Half the mismatched quotes I see come from a drawing that says "aluminum" and nothing else. If your RFQ doesn't name the alloy and temper, any number you get back is a guess. A shop that answers "we'll assume 6061" without flagging it is guessing too.
2. Where does the tolerance actually matter?
A housing bore at ±0.005 mm costs real money. A mounting hole at ±0.1 mm does not. Buyers who mark every dimension critical pay for precision in places that don't need it, or worse — they get quotes so far apart they can't compare them, because each shop interpreted the print differently. Circle the three or four dimensions that make the part work and let the rest ride standard ISO 2768-m.
3. What happens after sampling?
This is the question that separates a job shop from a production shop. Anyone can cut ten prototypes. Ask how the same part scales: which machines run it at volume, what the monthly output looks like, whether the fixtures get rebuilt for production or the prototype clamps just run slower. Our own answer, for reference — turned aluminum parts scale onto 50 CNC lathes and 70 Tsugami Swiss-type machines, up to around 5 million pieces a month across the floor; housings that need milled pockets stay on the machining centers. If a supplier can't describe that handoff in one sentence, sampling and production happen in two different places, and only one of them quoted to you.
4. Who owns the fixtures and the program?
At volume, your per-piece price lives in the workholding. Ask who pays for production fixtures and who keeps them. The answer changes both the tooling line item and what happens if you move the order later. I've watched buyers discover, mid-program, that their fixtures belong to a middleman they've never spoken to.
5. What does the finish add?
Anodizing Type II adds days and moves the part to a second process with its own tolerance drift — hard anodizing can grow dimensions by a couple of hundredths of a millimeter. If your bore is at the tight end and gets anodized after, say so on the drawing. Buyers who don't are the reason we keep re-anodize budget in the schedule.
6. When does the clock actually start?
Prototypes in 3–7 days and production in 7–15 days are honest numbers here, and surface treatment adds 3–7 on top. But those start after DFM is settled, not after the RFQ email. One unclear thread callout can sit in an inbox for two days. Buyers who answer DFM questions the same day get parts proportionally faster — it's the least used lever in the whole process.
A note on MOQ
We hold MOQ at 1 piece even for new designs, because sampling is how trust gets built, and because a buyer who starts at 50 pieces comes back at 5,000. Not every shop works this way. Some quote attractively at volume and refuse samples entirely — that's a signal about where their margin is.
One thing I still can't predict after thirteen years: which inquiries turn into programs. Last quarter a two-line email about anodized aluminum standoff pins outgrew a 40-page RFQ from a much bigger company. Ask good questions early; the rest tends to sort itself out.
Top comments (0)