The short answer
On CNC lot RFQs, a **go/no-go thread inspection** note is not the same as a **thread engagement length**, a **tap-drill depth**, or a general CMM sampling plan. Go/no-go means a thread plug or ring gage (GO must enter, NO-GO must not) used on a named set of holes or external threads, at a named sample size, at a named time—usually after tapping and, if a coating builds in the pitch, after or before finish as you specify. Silence on which threads are gaged, on 100% versus a sample, and on whether gaging happens after anodize or chem film, is what widens many [quote-new.php](https://3dwk.com/quote-new.php) **rates.v1.1** estimate bands—not the tap minutes alone.
This guide is for buyers packaging aluminum or stainless lot RFQs where CAD shows a thread callout and a notes cloud that says “inspect threads.” Illustrations use an **Example part** only—not a customer automation housing. Sibling notes live in [thread engagement length notes](https://3dwk.com/resources/thread-engagement-length-notes-cnc) and [thread depth callouts on blind tapped holes](https://3dwk.com/resources/thread-depth-callouts-blind-tapped-holes-cnc); [CMM sampling plans for CNC lots](https://3dwk.com/resources/cmm-sampling-plans-for-cnc-lots) cover measured features, not thread gages. Here we focus on **gage packaging**.
What go/no-go packaging means for quoting
A **GO gage** checks that the thread accepts a full-form member to the required length; a **NO-GO** checks that the pitch diameter is not oversized. That is a different stack from a pitch mic, a thread wire, or a CMM probe path. Process pages for automation aluminum and stainless ([CNC 3-axis Al 6061 automation](https://3dwk.com/en/cnc-3axis/al-6061/automation.html), [CNC 5-axis Al 6061 automation](https://3dwk.com/en/cnc-5axis/al-6061/automation.html), [CNC 3-axis SS 316](https://3dwk.com/en/cnc-3axis/ss-316.html)) assume a gage plan when lots mix structural taps with open cosmetic threads.
Do not bury “inspect all threads as needed” inside a notes cloud. Put **M5 × 0.8-6H STRUCTURAL: GO/NO-GO PLUG, SAMPLE 5 PER 25, AFTER TAP BEFORE CHEM FILM; COVER TAPS: FIRST-ARTICLE GAGE ONLY** on the PDF and mirror it in RFQ text. Background: [designing threads and tapped holes](https://3dwk.com/resources/designing-threads-and-tapped-holes), [what files to send for a CNC quote](https://3dwk.com/resources/what-files-to-send-for-cnc-quote).
Which holes, which sample, which moment
Name the thread family that is structural and the family that is only a cover screw. 100% go/no-go on every open cosmetic tap adds handling minutes without changing engagement, and it often triggers **needs_manual** when the coating sequence is still silent. A first-article gage plus a stated sample (for example five holes per lot of 25, or one hole per part on a named pattern) is usually enough when the process is stable. Say whether gaging is **before coating** (as-machined 6H) or **after** a finish that builds in the pitch—see [when to specify chem film after CNC aluminum](https://3dwk.com/resources/when-to-specify-chem-film-after-cnc-aluminum) and [how anodize choice changes CNC RFQ cost](https://3dwk.com/resources/how-anodize-choice-changes-cnc-rfq-cost). [Thread milling versus tapping](https://3dwk.com/resources/thread-milling-vs-tapping-cnc-buyers) is a process choice; it does not replace the gage note.
Aluminum 6061 and stainless 316 $/kg planning bands sit in **rates.v1.1** material tables; material cost is rarely the inspection story—gage time, coating sequence, and whether every hole is 100% checked are.
Gages versus CMM and FAI
A go/no-go plan is not a substitute for [first-article inspection reports](https://3dwk.com/resources/first-article-inspection-reports) on datums and fits, and it is not a CMM sampling plan. Keep both notes on the same PDF if you need them, but do not let one stand in for the other. If you also want a measured pitch diameter on a few holes, say so separately. Blind taps still need a usable engagement and a tap-drill depth; the gage only checks the form you can reach. Inserts change the parent hole and the finished gage: size the parent to the insert and gage the finished thread after installation if that is what you buy—see [thread inserts vs tapped holes](https://3dwk.com/resources/thread-inserts-vs-tapped-holes-aluminum).
Tolerance and inspection traps
Calling “inspect threads” without a gage type, mixing 100% go/no-go on cosmetic covers with a silent coating sequence, omitting sample size, or asking for both a full CMM thread scan and 100% gaging on every hole, all force **needs_manual**. Default non-critical covers to first-article or a light sample and put lot gaging on the structural family. Related: [ISO 2768 general tolerances on CNC RFQs](https://3dwk.com/resources/iso-2768-general-tolerances-cnc-rfq), [DFM checklist before an online CNC quote](https://3dwk.com/resources/dfm-checklist-before-online-cnc-quote).
Illustration 1 shows an **Example part** plate with labeled go/no-go sampling on structural M5 holes versus first-article-only cover taps on the same face.
Example part walkthrough
**Example part:** Aluminum 6061-T6 plate ~100×70×12 mm, four M5 × 0.8-6H structural taps and four M3 cover taps, ISO 2768-m general. With STEP + **M5 STRUCTURAL: GO/NO-GO PLUG, 5 PER 25, AFTER TAP BEFORE CHEM FILM; M3 COVER: FAI GAGE ONLY; NO 100% ON COVERS**, expect a usable automatic planning band on [quote-new.php](https://3dwk.com/quote-new.php). Same geometry with silent CAD and “inspect all threads 100% after finish” often lands DFM notes or **needs_manual**—without inventing any customer PO.
Illustration 2 contrasts a vague RFQ (“check every thread”) versus a labeled gage pack and the clearer estimate path.
What widens bands fastest
100% go/no-go on every cosmetic tap, gaging after a coating that was never sequenced, sample size left blank, and a CMM thread scan stacked on top of full-lot gaging. Quantity breaks help unit minutes but do not erase inspection 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 thread family with a **gage type, sample size, and before/after finish**, 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 gage questions rather than forcing a fake firm price.
Common questions
Is 100% go/no-go required on every tapped hole?
Not as a silent default under **rates.v1.1** estimates. Structural threads often deserve a stated sample or a 100% check; cover taps usually do not. Write the plan you will actually accept.
Can I write “inspect threads” and leave the method to the shop?
That leaves GO/NO-GO, pitch mic, and CMM all in play, and it leaves coating sequence open. Name the gage, the sample, and the moment.
When should I gage after coating instead of before?
When the finished pitch diameter must work after a coating that builds in the thread. If you gage only as-machined, say whether a pre-plate thread class or a post-coat check is required.
How does this differ from a CMM sampling plan?
CMM sampling covers measured sizes and positions. Go/no-go thread gages check accepted/rejected form on a named sample. Keep the two notes separate so neither is inferred from the other.