How to Order Custom Thread Gauges: 12 Details to Include in Your RFQ

A complete custom thread gauge RFQ helps the manufacturer calculate the correct gauge limits, select a suitable construction and provide an accurate price and lead time. Sending only a nominal size—such as “M12 gauge” or “1/2-inch thread gauge”—is rarely enough.

This guide explains the 12 details buyers should include when ordering custom thread plug gauges, thread ring gauges, pipe thread gauges, setting plugs and drawing-defined inspection gauges.

Why Custom Thread Gauge RFQs Are Often Delayed

Thread gauges are manufactured to specific limits. Two gauges with the same nominal diameter may be different because of their pitch, thread form, tolerance class, workpiece designation, standard, wear allowance or special drawing requirements.

An incomplete RFQ can result in:

• Repeated technical questions
• Incorrect plug or ring gauge selection
• Wrong tolerance class
• Missing GO or NO-GO members
• Unquoted calibration costs
• Lead-time changes after order confirmation
• A gauge that does not match the workpiece drawing

The following 12 points provide a practical RFQ structure for purchasing and quality teams.

1. State Whether the Workpiece Thread Is Internal or External

First identify the thread being inspected:

• Internal thread: tapped hole, nut, threaded insert, housing or internal fitting
• External thread: bolt, stud, shaft, threaded pin or external fitting

Internal threads usually require a thread plug gauge. External threads usually require a thread ring gauge.

Do not describe the gauge only as “male” or “female.” State both the workpiece-thread type and required gauge type to eliminate ambiguity.

2. Provide the Complete Thread Callout

The complete thread designation is one of the most important RFQ details. Include diameter, pitch or threads per inch, thread series and tolerance class.

Incomplete Description	Better RFQ Description
M12	M12 × 1.75-6H internal thread
1/4 UNC	1/4-20 UNC-2B internal thread
1/4 UNF	1/4-28 UNF-2A external thread
1/4 pipe thread	G 1/4 internal BSPP thread
1/4 NPT	1/4-18 NPT internal thread
ACME gauge	1/2-10 ACME-2G internal thread
Special thread	Drawing number, revision and complete dimensional limits

If the thread callout is unclear, send the component drawing rather than estimating the specification.

3. Identify the Applicable Thread and Gauging Standard

The manufacturer needs to know which standard controls the thread and gauge limits. Examples include:

• ISO metric thread and gauging requirements
• ASME Unified inch thread and gauge requirements
• BSPP or BSPT pipe-thread standards
• NPT or NPTF pipe-thread standards
• ACME thread standards
• API or other industry-specific requirements
• Customer drawings or internal company specifications

ISO 1502 specifies gauges and gauging for ISO general-purpose metric screw threads. ASME B1.2 addresses gauges and gauging for Unified inch screw threads. The purchase order should identify the applicable requirement rather than assuming every manufacturer will use the same system.

Use our thread size charts as an initial reference for Metric, UNC, UNF, BSP, NPT and ACME threads.

4. Specify the Required Gauge Type

Tell the manufacturer exactly what must be supplied. Common options include:

Gauge Type	Primary Use
Thread plug gauge	Inspection of internal threads
Thread ring gauge	Inspection of external threads
Setting plug	Setting or checking a compatible adjustable thread ring gauge
Taper pipe thread plug gauge	Inspection of internal taper pipe threads
Taper pipe thread ring gauge	Inspection of external taper pipe threads
Master gauge	Reference or setting applications defined by the inspection system
Special functional gauge	Inspection of drawing-defined or application-specific features

If you are unsure which gauge is needed, send the workpiece drawing and explain the inspection objective.

5. Confirm GO, NO-GO or Complete-Set Requirements

A quotation may cover a single member or a complete GO/NO-GO set. Clearly state whether you need:

• GO member only
• NO-GO member only
• Complete GO and NO-GO set
• Thread ring gauges plus setting plug
• Working gauges plus master or reference gauges

When comparing quotations, check that every supplier has included the same members. A lower price may reflect an incomplete set.

6. Attach the Drawing and State Its Revision

For special threads or custom inspection gauges, attach the controlled drawing and identify its revision. Commonly accepted information can include:

• PDF engineering drawing
• DXF or DWG file
• STEP or other 3D model
• Inspection plan
• Existing gauge drawing
• Photographs with clearly marked dimensions
• Sample part, where appropriate

The drawing should identify which dimensions are workpiece limits and which are gauge-design requirements. If only the workpiece drawing is available, tell the gauge manufacturer that the gauge limits still need to be calculated.

7. Describe Special Limits and Inspection Conditions

Standard gauges can usually be manufactured from recognized specifications. Custom applications may require additional information, such as:

• Special pitch-diameter limits
• Oversize or undersize thread condition
• Plating or coating allowance
• Pre-plating or post-plating inspection
• Left-hand thread
• Modified thread form
• Required engagement length
• Restricted access around the thread
• Blind-hole depth or clearance limitations
• Workpiece temperature or special operating environment

When coating is involved, specify whether the thread dimensions apply before or after coating. This can materially change the required gauge limits.

8. Define Gauge Material, Hardness and Coating Needs

The manufacturer can recommend a material based on the gauge size, tolerance and inspection volume, but the buyer should disclose any special durability requirement.

RFQ Information	Why It Matters
Workpiece material	Abrasive or hardened parts may influence wear considerations
Expected inspections per day	High-volume use may justify a different material or construction
Gauge material requirement	Customer specifications may require tool steel, carbide or another material
Hardness requirement	May be defined by a customer standard or quality plan
Coating requirement	Can affect wear resistance, corrosion behavior and cost
Storage environment	Humidity and handling conditions may affect protection requirements

A standard hardened tool-steel gauge may be suitable for many applications. Higher inspection volumes or abrasive workpieces may justify discussing carbide or another wear-resistant option.

9. State the Required Quantity and Repeat-Order Plan

Include the exact quantity for each gauge and identify whether the project is:

• A single prototype or replacement gauge
• A set for one inspection station
• Multiple sets for several production lines
• A distributor or private-label order
• A repeat program requiring future replacement gauges

If several production sites will use the gauge, consider whether each gauge needs its own serial number and certificate.

10. Define Marking, Handle and Packaging Requirements

Gauge marking helps prevent selection errors and supports calibration control. Specify what must appear on the gauge or handle.

• Thread size and tolerance class
• GO or NO-GO identification
• Buyer part number
• Gauge serial number
• Drawing number and revision
• Manufacturer identification
• Calibration date or identification, where required

Distributors may also require neutral packaging, private-label packaging, custom labels, barcode information or branded storage cases.

11. Specify Calibration and Documentation Requirements

Do not write only “certificate required.” State which documents and measured values your quality system needs.

• Manufacturer conformity or inspection report
• Actual measured-value report
• Calibration certificate
• Accredited third-party calibration
• Traceability information
• Material certificate
• Hardness report
• Custom inspection-report format

Also confirm whether the document must show:

• Gauge serial number
• Buyer part number
• Drawing revision
• Measured parameters and results
• Measurement uncertainty
• Environmental conditions
• Traceability statement

Calibration scope can affect both price and delivery time, so it should be confirmed before the purchase order is issued.

12. Include Delivery Timing and Destination

State the required delivery date, destination country and preferred shipping method. Separate the requested dates for:

• Technical drawing or gauge-design approval
• Prototype or first-piece gauge
• Calibration completion
• Bulk gauge production
• Final shipment

For urgent orders, identify which date is genuinely critical. The manufacturer may be able to prioritize the gauge production while the final third-party calibration follows a separate schedule.

Standard Gauge vs Custom Gauge RFQ

RFQ Area	Standard Thread Gauge	Custom Thread Gauge
Thread information	Complete standard callout	Drawing and complete special limits
Gauge design	Defined by applicable standard	Requires engineering review
Approval	Specification confirmation	May require gauge drawing approval
Lead time	Depends on size and availability	Depends on design, material and validation
Documentation	Standard or selected certificate	Custom report and measured values may be required
Repeat orders	Ordered by standard specification	Must reference approved drawing and revision

What Happens After You Send the RFQ?

A structured custom gauge project normally follows these stages:

1. Requirement review: The manufacturer checks the drawing, thread callout, standard and inspection objective.
2. Technical clarification: Missing tolerances, gauge members, coating conditions or documents are confirmed.
3. Quotation: Price, quantity, material, certificate scope and estimated lead time are provided.
4. Gauge design: Custom gauge limits and construction are prepared where required.
5. Buyer approval: The buyer confirms the specification or gauge drawing.
6. Manufacturing: Material preparation, heat treatment, grinding, lapping, finishing and marking are completed as applicable.
7. Inspection and calibration: Required characteristics are checked and documentation is prepared.
8. Packing and shipment: The gauge, certificate and identified accessories are packed according to the order.

What Determines Custom Thread Gauge Price?

Custom thread gauge cost is influenced by:

• Gauge type and physical size
• Thread complexity and tolerance
• GO/NO-GO and setting-gauge scope
• Material, hardness and coating
• Engineering and drawing requirements
• Inspection and calibration scope
• Custom marking and packaging
• Quantity and delivery urgency

A meaningful price comparison requires every supplier to quote the same specification, gauge members and documents.

Copyable Custom Thread Gauge RFQ Template

Frequently Asked Questions

Can a custom thread gauge be manufactured from a workpiece drawing?

Yes. The manufacturer can review a controlled workpiece drawing and calculate or confirm the gauge requirements. The buyer should identify the applicable standard, drawing revision and inspection objective.

What file formats can I send for a custom gauge quotation?

Common formats include PDF, DXF, DWG and STEP. A clear sketch, existing gauge information or sample part may also help, but controlled drawings are preferable for final approval.

Can I order one custom thread gauge?

Prototype and low-quantity custom gauges may be available depending on the size, material, construction and calibration requirements. Send the complete specification for confirmation.

Does a custom thread ring gauge need a setting plug?

Some adjustable thread ring gauge systems require the correct setting plug and setting procedure. Confirm whether the setting plug must be included in the quotation.

How long does a custom thread gauge take to manufacture?

Lead time depends on engineering review, size, material, heat treatment, gauge complexity, quantity and calibration scope. A complete RFQ allows the manufacturer to provide a more reliable schedule.

What certification should I request with a custom gauge?

That depends on your quality system. Options may include a manufacturer inspection report, actual measured-value report, calibration certificate, traceability information or accredited third-party calibration.

Additional Buyer Notes

• Hole Geometry and Chamfer Clearance: Specify whether internal tapped holes are through holes or shallow blind holes.
• Helical Wire Thread Insert (STI) Specs: If tapping holes for wire inserts (e.g., Helicoil), standard plug gauges will fail.
• Multi-Start Pitch and Lead Callouts: For power transmission screws (such as Acme or Trapezoidal leadscrews), distinguish between Pitch and Lead on multi-start threads (e.g., 2-start or 4-start) to ensure correct gauge helix angle alignment.
• Reverse-Engineering Protocols Without Prints: If replacing a worn tool without an original engineering print, follow our technical protocol on replacing thread gauges without a drawing to extract physical dimensions safely.