A thread note such as “M6” is rarely enough for a production quotation. The machinist needs to know the thread form, pitch, class or fit, useful depth, material and how acceptance will be checked. The buyer also needs to distinguish a critical assembled thread from a cosmetic or low-load feature.
Put the complete thread definition on the drawing
Record the nominal size, pitch, internal or external form, tolerance class and handedness. Identify a nonstandard thread with its controlling specification or a dimensioned detail. For blind holes, separate drill depth from full thread depth; tool entry and runout mean the two are not interchangeable.
If the thread mates with a supplied component, include that component or its controlled specification in the RFQ. A physical sample can help resolve ambiguity, but it should not replace a revision-controlled drawing.
- Size, pitch, form and fit
- Full thread length or useful engagement depth
- Handedness and any entry chamfer or relief
Show the functional datums
A threaded hole may be the right size but still fail assembly because its axis is misplaced or tilted. Dimension the thread location from the datums that locate the real mating part. For an external thread on a turned component, identify any runout relationship to sealing or bearing surfaces.
Call out only the geometric controls that matter. Applying the same tight positional or coaxial requirement to every thread makes quotations harder to compare and may add inspection time without improving fit.
Confirm material and finishing sequence
Aluminum, stainless steel and hardened steel may require different tooling and chip-control plans. Plating, anodizing or other coating can change thread fit. State whether the gauge acceptance applies before or after finish, and whether masking is required.
Ask how blind holes will be cleaned and protected. Chips left in a threaded cavity can interfere with a gauge and later contaminate the assembly.
- Material grade and condition
- Finish type and thread masking requirements
- Cleaning and edge-break expectations
Agree on gauges and evidence
For standard threads, a calibrated go/no-go gauge is a practical acceptance tool when the specified class and gauge standard match. Functional assembly checks may also be useful, especially for special threads, but need a defined mating part and pass criteria. A visual check alone cannot establish thread fit.
Define the sample plan, first-article evidence and records required for repeat orders. Identify who supplies any special gauge and when it must be available.
- Gauge type and applicable class
- First-article and batch sampling requirements
- Nonconformance and rework approval path
Build a quote-ready package
Send the current PDF drawing together with a 3D model, quantity by release, material, finish, required documentation and target delivery window. Flag mating parts and critical threads in a short RFQ note. If a design detail is undecided, request a DFM question before the supplier commits to a price.
A complete thread callout makes quotations more comparable and helps the inspection report answer the assembly question. Review the first article with the actual mating component before releasing a production lot.
Turn this machining question into a manufacturable part
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