The short answer
On turned-shaft RFQs, a **thread relief and runout note** is not the same as a [shoulder fillet versus undercut](https://3dwk.com/resources/shoulder-fillet-vs-undercut-cnc-turned-shafts), a [GD&T circular-runout callout](https://3dwk.com/resources/concentricity-vs-runout-callouts-cnc-shafts), or a general thread size. Thread runout is the incomplete thread that remains when a threading tool exits; a relief groove is the intentional empty band that lets a full-form thread reach a shoulder or a gauge plane. Silence on whether the last usable thread must sit hard against a shoulder, on relief width and diameter, and on whether a short incomplete runout is allowed, is what widens many [quote-new.php](https://3dwk.com/quote-new.php) **rates.v1.1** estimate bands—not the extra seconds of a plunge groove alone.
This guide is for buyers packaging turned RFQs where a thread runs toward a shoulder, a seal face, or a gauge length with no named relief or incomplete-thread allowance. Illustrations use an **Example part** only—not a customer shaft. Sibling notes live in [designing threads and tapped holes](https://3dwk.com/resources/designing-threads-and-tapped-holes) and the [turned stainless shaft drawing guide](https://3dwk.com/resources/turned-stainless-shaft-drawing-guide); here we focus on **thread-relief packaging** so estimators do not have to guess whether an M12 must be full-form to the shoulder.
What thread relief means for quoting
A **thread relief** is a turned groove, or a specified incomplete-thread length, that clears the thread tool and the mating part. It is not the same as a seating-face undercut, and a general “thread to shoulder” cloud does not tell the shop whether a 1 mm incomplete runout is acceptable. Process pages for stainless turning and milling ([CNC turning SS 316 robotics](https://3dwk.com/en/cnc-turning/ss-316/robotics.html), [CNC turning SS 316](https://3dwk.com/en/cnc-turning/ss-316.html), [CNC 3-axis SS 316](https://3dwk.com/en/cnc-3axis/ss-316.html)) assume relief and runout notes when lots mix shoulder-adjacent threads with gauged lengths.
Do not bury “full thread as needed” inside a notes cloud. Put **M12 × 1.75, FULL FORM TO SHOULDER A, RELIEF WIDTH 2.5 / BELOW MINOR, OR ALLOW 1.5 INCOMPLETE RUNOUT** 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), [thread engagement length](https://3dwk.com/resources/thread-engagement-length-notes-cnc).
Shoulders, gauges, and incomplete runout
A thread that must accept a nut hard against a shoulder needs a relief, or the last incomplete crests will stop the nut short. A thread that only has to gauge over a named length can often keep a short tool runout beyond the gauge plane—if you write that length. [Keyway callouts on CNC turned shafts](https://3dwk.com/resources/keyway-callouts-on-cnc-turned-shafts) and [knurling](https://3dwk.com/resources/knurling-on-cnc-turned-shafts) that sit next to a thread should show the gap so a relief and a knurl do not collide.
Stainless 316 bar $/kg planning bands sit in the mid-commodity stainless range under **rates.v1.1** material tables; material cost is rarely the relief story—tool exit, incomplete crests, and shoulder seating are.
Relief width, diameter, and tool nose
Name relief width, relief diameter (or “below minor diameter”), and whether a radius or a square tool is acceptable in the groove. A relief that is narrower than the tool nose, or that leaves a diameter still inside the thread major, does not actually clear the tool. [When to call out undercuts on a CNC RFQ](https://3dwk.com/resources/when-to-call-out-undercuts-on-cnc-rfq) covers undercuts in general; here the undercut exists only to make the thread usable.
Tolerance and inspection traps
Calling “full thread to shoulder” without a relief, mixing a tight shoulder axial position with an unspoken die-cut runout, or asking for 100% optical photos of every incomplete crest, all force **needs_manual**. Default non-critical runout length to a written allowance and put a functional relief only where a nut, coupling, or gauge must sit flush. Related: [ISO 2768 general tolerances on CNC RFQs](https://3dwk.com/resources/iso-2768-general-tolerances-cnc-rfq), [go/no-go thread inspection notes](https://3dwk.com/resources/go-no-go-thread-inspection-notes-cnc-lots).
Illustration 1 shows an **Example part** shaft with a labeled relief ahead of shoulder A versus a short allowed incomplete runout beyond a gauge length on the same blank.
Example part walkthrough
**Example part:** Stainless 316 turned shaft ~Ø20 × 80 mm, M12 × 1.75 thread approaching shoulder A, relief width 2.5 mm below minor diameter, or alternatively 1.5 mm incomplete runout allowed past a 16 mm gauge length, ISO 2768-m general. With STEP + **M12 × 1.75 FULL FORM TO SHOULDER A; RELIEF W2.5 / BELOW MINOR; GAUGE LENGTH 16 IF NO RELIEF**, expect a usable automatic planning band on [quote-new.php](https://3dwk.com/quote-new.php). Same geometry with silent CAD and “thread to shoulder as needed” often lands DFM notes or **needs_manual**—without inventing any customer PO.
Illustration 2 contrasts a vague RFQ (“full thread, no incomplete crests”) versus a labeled relief-and-runout pack and the clearer estimate path.
What widens bands fastest
Unlabeled mix of shoulder-adjacent threads and free-end threads, reliefs that still sit on the major diameter, gauge lengths left unspoken, and 100% cosmetic inspection of every runout. Quantity breaks help unit minutes but do not erase thread-exit ambiguity—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 each shoulder-adjacent thread with a **relief or a named incomplete-runout allowance**, 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 relief questions rather than forcing a fake price.
Common questions
Does every external thread need a relief groove?
No. A free-end thread, or a thread whose last usable turn sits well before a shoulder, can often keep a short incomplete runout if you write the gauge length. A nut or coupling that must seat on a shoulder usually needs a relief.
Can I write “full thread to shoulder” and leave the model as-is?
Only if the CAD already shows a clear relief below the minor diameter. A sharp thread that vanishes into a shoulder in the STEP file is not rescued by a notes cloud. Update CAD or add a relief so the shop and the estimate see the same intent.
Is thread runout the same as GD&T circular runout?
No. Incomplete thread runout is a threading-tool exit condition. [Circularity vs cylindricity](https://3dwk.com/resources/circularity-vs-cylindricity-cnc-shafts) and concentricity-versus-runout notes describe geometry of a diameter, not missing crests. Keep the two notes separate.
How should I call out a thread that sits next to a knurl or keyway?
Show the gap between the last full thread (or the relief) and the knurl or keyway start. Leaving only the thread size leaves the estimator guessing whether a 1 mm leftover band is intentional.