In brief
A useful pipe-thread drawing identifies the thread system and size, the applicable standard and tolerance requirements, the mating and sealing geometry, and how conformity will be checked. A note saying only BSP or quarter-inch thread leaves essential decisions unresolved.
Start with a complete designation
Select the thread system before writing the callout. ASME B1.20.1 covers NPT dimensions and gauging; ISO 7-1 and ISO 228-1 address different pipe-joint systems. Use the designation rules in the edition specified by the drawing owner, rather than combining abbreviations from different standards.
Use this preparation format for each port: Port ID; internal or external; thread designation from the selected standard; standard and edition; thread length or depth requirement; sealing-detail reference; inspection reference. Fill these fields from the released design, then place the appropriate standard callout on the drawing. This is an information checklist, not a replacement for the standard designation.
References: ASME B1.20.1: Pipe Threads, General Purpose, Inch; ISO 7-1:1994: Pressure-tight joints made on the threads; ISO 228-1:2000: Joints not made pressure-tight on the threads
Connect the callout to the actual feature
Point the callout to the correct port or thread and distinguish it from a nearby bore. Show the surrounding geometry needed to manufacture and inspect the interface. Where two ports look similar, label them individually rather than relying on the reader to infer that they are identical.
- Internal or external feature identified
- Thread system, nominal size and required designation complete
- Relevant thread length or depth requirements stated in the correct standard context
- Blind-hole clearance and adjacent bore requirements defined where applicable
- Sealing face, seat, shoulder and any finish requirements identified
- Port location and orientation related to the drawing datums
Specify acceptance separately from identification
Identifying a sample thread is not the same task as accepting a manufactured thread. Record the agreed gauging reference and any additional characteristics that need inspection. Clarify whether requirements apply before or after coating or other finishing operations.
A mating-part assembly check can be requested for a defined purpose, but it should not silently replace the specified dimensional or gauging requirements. Similarly, a thread inspection does not by itself verify the leakage performance of the finished assembly.
| Drawing item | Question to resolve |
|---|---|
| Thread designation | Can the required system and tolerance be identified without assumptions? |
| Finish | Which requirements apply to the final delivered condition? |
| Gauging | Which reference and acceptance procedure govern the check? |
| Sealing feature | Is its geometry and inspection scope defined separately? |
| Records | Which results must be supplied with the parts? |
References: ASME B1.20.1: Pipe Threads, General Purpose, Inch
Release one agreed drawing package
Before asking for a revised price, identify what changed. A thread change may also change the mating part, seal or inspection requirement, so do not send a revised model with an unchanged drawing note and expect the supplier to reconcile it.
Use a short review record: document revision, unresolved question, agreed answer and responsible approver. Keep proposed alternatives separate until the drawing owner accepts them. This makes quotation comparisons more useful and reduces the chance that suppliers price different assumptions.
Sources & scope
Source pages checked on 2026-09-24. Publisher summaries and manufacturer references help identify the subject; they do not replace the specified standard or a reviewed part drawing. The checklists are editorial guidance for quotation preparation. External suppliers’ capabilities and certifications are not BOREVIA claims.
- ASME B1.20.1: Pipe Threads, General Purpose, Inch
Publisher overview of dimensional and gauging scope. Consult the specified edition for acceptance requirements.
- ISO 7-1:1994: Pressure-tight joints made on the threads
Publisher description of thread dimensions, tolerances and designation.
- ISO 228-1:2000: Joints not made pressure-tight on the threads
Publisher abstract describing parallel threads and sealing outside the threads.
From preparation to a defined RFQ
Bring the drawing and the open questions
State the part revision, material, quantity and inspection requirements. Pricing and feasibility need a review of the actual request.
Request an engineering quote