The short answer
Multi-setup CNC parts fail quotes when the PDF has rich GD&T but **no coherent datum scheme** across flips. Define primary/secondary/tertiary datums that survive each setup so [quote-new.php](https://3dwk.com/quote-new.php) **rates.v1.1** estimate bands stay usable instead of flipping to **needs_manual**.
This guide is for buyers RFQing prismatic parts that need two or more orientations. Illustrations use an **Example part** only—not a customer fixture drawing. Related mill+turn context: [milled and turned features on one CNC part](https://3dwk.com/resources/milled-and-turned-features-on-one-cnc-part).
Why datum schemes dominate multi-setup risk
Each reclamp restarts how the shop finds the part. If Setup 1 machines to Datum A and Setup 2 “assumes” the same faces without calling them, positional stacks explode. Online parsers treat dense GD&T as inspection time; ambiguous datums widen bands further. Background: [GD&T basics for buyers](https://3dwk.com/resources/gdt-basics-for-buyers), [flatness / parallelism / perpendicularity](https://3dwk.com/resources/flatness-parallelism-perpendicularity-machined-parts), [DFM checklist before an online CNC quote](https://3dwk.com/resources/dfm-checklist-before-online-cnc-quote), [first article inspection reports](https://3dwk.com/resources/first-article-inspection-reports).
A housing that looks “one setup” in CAD often needs a flip for the opposite pocket, a side approach for a port, or a soft-jaw reclamp for a thin wall. The datum scheme is the contract that keeps those moves measurable.
Primary, secondary, tertiary that shops can actually use
Prefer a large stable face as primary (A), a long edge or pair of pins as secondary (B), and a stop as tertiary (C)—classic 3-2-1. Do not nominate a tiny chamfer as A just because CAD labeled it first. Soft materials (e.g. PA66, machine-time coeff ×0.8 under **rates.v1.1** estimates) need larger contact areas than 17-4PH (×1.4) so clamps do not dig in.
Call which features are finished in which setup. “All datums after final” is not a scheme—it is a hope. If a sealing face is Datum A but anodize growth will move it, say whether A is pre-finish or post-skim.
Setup order notes that stabilize estimates
State a preferred order when function allows: e.g. mill floor and bores → flip for opposite pockets → side setups for undercuts. If continuous 5-axis is optional, say positional indexing is acceptable—blanket “must be 5-axis” raises machine-class assumptions. See [3-axis vs 5-axis for buyers](https://3dwk.com/resources/3-axis-vs-5-axis-cnc-for-buyers) and [five-axis aluminum housing tips](https://3dwk.com/resources/five-axis-aluminum-housing-design-tips).
Illustration 1 shows an **Example part** datum map across two flips with A/B/C surviving both setups.
Tolerance discipline across flips
Default non-mates to ISO 2768-m. Put true position on bolt patterns relative to the same datums used in fixturing. Avoid “±0.01 all over” plus a second stack of position frames—that doubles inspection narrative without buying function. Pair form controls only where mates need them. Related: [CMM vs optical measurement](https://3dwk.com/resources/cmm-vs-optical-measurement-machined-parts).
Hot alloys (IN718/IN625 time coeff ×2.5, CoCr ×2.2 under **rates.v1.1** estimates) amplify multi-setup time; lines above configured USD thresholds auto-route to **needs_manual**. Bar $/kg planning bands (estimates): PA66 ~5, 17-4PH ~9, IN718 ~55, IN625 ~60. Extra flips on hot alloys hurt more than the same flips on 6061.
Soft jaws, pins and transfer datums
If Setup 2 locates on a finished bore from Setup 1, say so on the PDF. Transfer datums (machined pads for later clamps) are legitimate—draw them. Soft-jaw sketches help when envelopes are irregular; they do not need customer logos or proprietary fixture photos. Related: [press-fit pins and bushings](https://3dwk.com/resources/press-fit-pins-bushings-cnc-housings), [what files to send for a CNC quote](https://3dwk.com/resources/what-files-to-send-for-cnc-quote), [pockets / thin walls / undercuts](https://3dwk.com/resources/cnc-pockets-thin-walls-undercuts).
Finish and datum interaction
Anodize growth or plating thickness can move a sealing face relative to a pre-finish datum. Call whether critical datums are post-finish skimmed. Type II vs Type III notes belong on the finish block—see [how anodize choice changes CNC RFQ cost](https://3dwk.com/resources/how-anodize-choice-changes-cnc-rfq-cost). Cosmetics on non-datum walls should not redefine A/B/C.
Illustration 2 contrasts a vague “machine complete, datums TBD” pack versus a setup-ordered datum block and the clearer estimate path.
Example part walkthrough
**Example part:** 6061-T6 L-bracket, ~90×60×40 mm, two setups (floor+bores then opposite pocket), Datum A = large floor, B = long edge, C = stop face, ISO 2768-m general, Ø6 H7 bore true position 0.08 to A|B|C, optional clear Type II. With STEP + PDF datum scheme, expect an automatic planning band on [quote-new.php](https://3dwk.com/quote-new.php). Same envelope with “±0.01 everywhere” and no A/B/C often lands DFM notes or manual review—without inventing any customer PO.
Inspection sampling across setups
Qty 2 multi-setup parts often imply near-full check of position frames after each critical reclamp story. Qty 25 may allow sampling if your quality agreement allows it. If the PDF says “100% CMM all GD&T after every setup,” inspection stays variable-heavy and the mid rises even when spindle time is modest. Say whether FAIR is once per lot.
What to do next
Draw datums that survive each flip, then upload on [quote-new.php](https://3dwk.com/quote-new.php). Service pages: [CNC machining](https://3dwk.com/cnc-machining-service.php), [materials](https://3dwk.com/materials.php). Treat **rates.v1.1** min/mid/max as estimates, not invoices. If the UI shows needs_manual, answer datum questions rather than forcing a fake firm price.
Common questions
Do I need GD&T frames on every face for multi-setup parts?
No. Call datums once and apply position/form only on functional mates. Dense frames without a scheme still widen bands.
Can I leave setup order to the shop?
Often yes for simple prismatics—if datums are clear. Complex undercuts or thin walls benefit from a preferred order note so estimate assumptions match intent.
Will more datums always tighten the mid estimate?
Not if they conflict. Conflicting A/B/C across views forces clarification. Prefer one coherent scheme over three competing ones.
Does mill-turn change the datum story?
Yes—turned registers and milled flanges should share one surviving datum narrative. See the mill+turn guide linked above rather than pasting prismatic-only notes onto a shaft flange.