The short answer
On a CNC RFQ, a **chamfer** and a **fillet** are not interchangeable edge-break notes. A chamfer is a flat break (often 45°) that clears sharp edges for handling and assembly. A fillet is a radius blend that spreads stress and can change cutter access, cycle time, and finish intent. Silence on **which edges** and **which break type** is what widens many [quote-new.php](https://3dwk.com/quote-new.php) **rates.v1.1** estimate bands—not the blank size alone.
This guide is for buyers packaging prismatic aluminum RFQs where drawings say “break all edges” without a size or style. Illustrations use an **Example part** only—not a customer bracket. Related edge and corner notes live in [edge break chamfer deburr callouts](https://3dwk.com/resources/edge-break-chamfer-deburr-callouts-cnc), [fillet vs sharp internal corners](https://3dwk.com/resources/fillet-vs-sharp-internal-corners-cnc-rfq), and [sharp internal corners on CNC quotes](https://3dwk.com/resources/sharp-internal-corners-cnc-quotes); here we focus on **chamfer vs fillet labeling** so estimators do not guess.
What chamfer and fillet mean for quoting
A chamfer removes a triangular wedge—common callouts are C0.2–C1.0 or 0.5×45°. A fillet blends with radius R; internal fillets need cutter diameter clearance, external fillets may be ball-nose or form. Process pages for automotive aluminum ([CNC 3-axis Al 6061 automotive](https://3dwk.com/en/cnc-3axis/al-6061/automotive.html), [CNC 5-axis Al 6061 automotive](https://3dwk.com/en/cnc-5axis/al-6061/automotive.html), [CNC turning Al 6061 automotive](https://3dwk.com/en/cnc-turning/al-6061/automotive.html)) assume edge-break notes when lots mix handling edges, sealing lands, and cosmetic faces.
Do not bury “break sharp” inside a notes cloud. Put **CHAMFER C0.5×45° EXT EDGES** or **FILLET R0.5 EXTERNAL / R1.0 INTERNAL MIN** on the PDF and mirror it in RFQ text. Background: [DFM checklist before an online CNC quote](https://3dwk.com/resources/dfm-checklist-before-online-cnc-quote), [what files to send for a CNC quote](https://3dwk.com/resources/what-files-to-send-for-cnc-quote).
Size bands, tool access and finish
Tiny chamfers (C0.1–C0.2) often ride with a deburr pass under **rates.v1.1** estimates; large chamfers or long runs add programmed toolpaths. Internal fillets smaller than the planned end mill force tool changes or EDM/hand work that widen bands. Soft stock (PA66 time coeff ×0.8) still needs clear keep-outs on sealing lands. Harder alloys (17-4PH ×1.4, IN718/IN625 ×2.5) amplify tool wear on long fillet blends; aggressive R0.2 internal asks on hot alloys frequently auto-route toward **needs_manual** when mid-line bands exceed planning thresholds.
If anodize or powder follows, say whether the break is as-machined or post-finish—see [as-machined before Type II anodize](https://3dwk.com/resources/as-machined-before-type-ii-anodize) and [how anodize choice changes CNC RFQ cost](https://3dwk.com/resources/how-anodize-choice-changes-cnc-rfq-cost).
Bar $/kg planning bands (estimates only): PA66 ~5, 17-4PH ~9, IN718 ~55. Material cost is rarely the edge-break story—tool access and cosmetic keep-outs are.
Sealing lands, cosmetics and clamp keep-outs
O-ring lands, gasket faces, and painted edges hate uncontrolled chamfers that undercut a seal. Soft-jaw or vise clamps can witness on broken edges if keep-outs are silent—see [soft jaws vs vise CNC production lots](https://3dwk.com/resources/soft-jaws-vs-vise-cnc-production-lots). Name **NO BREAK** on sealing lands the same way you name support keep-outs on AM RFQs.
Tolerance and inspection traps
Calling “break all edges 0.5 max” without distinguishing chamfer vs fillet leaves CMM and visual criteria ambiguous. Default non-critical envelope to ISO 2768-m and put functional edge sizes only where assembly or stress needs them. Related: [GD&T callouts that raise CNC quote bands](https://3dwk.com/resources/gdandt-callouts-that-raise-cnc-quote-bands), [datum schemes for multi-setup CNC parts](https://3dwk.com/resources/datum-schemes-for-multi-setup-cnc-parts), [CMM sampling plans for CNC lots](https://3dwk.com/resources/cmm-sampling-plans-for-cnc-lots).
Illustration 1 shows an **Example part** with labeled external chamfer C0.5×45° versus an external fillet R0.5 on the same blank envelope.
Example part walkthrough
**Example part:** 6061-T6 plate ~120×80×12 mm, two external long edges for handling, one sealing land Ø40 that must stay sharp, ISO 2768-m general. With STEP + **CHAMFER C0.5×45° ON EXT HANDLING EDGES ONLY; SEALING LAND — NO BREAK**, expect a usable automatic planning band on [quote-new.php](https://3dwk.com/quote-new.php). Same geometry with silent CAD and “break all sharp / fillet OK” often lands DFM notes or **needs_manual**—without inventing any customer PO.
Illustration 2 contrasts a vague RFQ (“break edges / radius OK”) versus a labeled chamfer/fillet/no-break block and the clearer estimate path.
What widens bands fastest
Unlabeled mix of chamfer and fillet asks, “R0.2 all internal” without cutter access, sealing lands left in a global break note, and 100% visual of every broken edge. Quantity breaks help unit minutes but do not erase keep-out risk—see [how quantity breaks change CNC unit cost](https://3dwk.com/resources/how-quantity-breaks-change-cnc-unit-cost) and [what needs_manual means](https://3dwk.com/resources/what-needs-manual-means-preliminary-quote).
What to do next
Mark **CHAMFER** or **FILLET** with size, name **NO BREAK** keep-outs, 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 the edge-break questions rather than forcing a fake firm price.
Common questions
Is a small chamfer always cheaper than a fillet?
Often for external handling edges, yes—under **rates.v1.1** estimates a short chamfer pass is simpler than a radius blend. Internal fillets are driven by cutter diameter, not preference alone.
Can I write “break or radius OK”?
Avoid it. Estimators cannot pick a toolpath family from that note. Pick chamfer or fillet per edge family.
How do anodize faces change the choice?
Cosmetic faces may prefer a controlled chamfer that does not undercut dye edges. State finish order—see [how anodize choice changes CNC RFQ cost](https://3dwk.com/resources/how-anodize-choice-changes-cnc-rfq-cost).
Should internal sharp corners follow the same habit?
Yes. Internal corner radius is a sibling topic—see [fillet vs sharp internal corners](https://3dwk.com/resources/fillet-vs-sharp-internal-corners-cnc-rfq)—but external chamfer vs fillet remains mandatory on production RFQs.