Compare a measured straight-thread pitch with a documented source interval, convert mm, inches and TPI, and derive lead from an independently sourced start count without identifying or approving a thread.
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Inputs that matter
One named straight, constant-pitch thread record and basis; responsible reviewer and revision; exact standard, drawing or controlled-source record; exact source-owned thread designation without inferred omissions; source pitch lower and upper entries in millimetres, inches or TPI plus owner/revision/locator; one measured span in millimetres or inches; exact whole pitch-interval count; instrument, corresponding-point method, resolution, date and measurement locator; exact whole thread-start count with its independent source; optional independent reported lead in millimetres or inches with its own owner/revision/locator; and an explicit downstream identity, fit, machining, quality, disposition and safety boundary
Output to expect
Source pitch entries normalized to an inclusive pitch interval in millimetres, including correct reversal of TPI endpoints; measured span and exact interval count; measured pitch in millimetres and TPI classified below, inside or above the source interval with signed endpoint/midpoint differences and nearest-boundary distance; source-derived lead interval and measured-pitch-derived lead from the exact start count; optional independent reported lead classified against that source-derived lead interval with derived-minus-reported residual; complete standard/designation/source/measurement/start/reviewer/boundary evidence; deliberate page-session snapshots, copy/Markdown/print/share actions; and stable Project outputs that keep thread identity, standard/class verification, fit/compatibility, geometry/tolerance, machining, part quality/disposition and safety/work authorization false
How it works
Validate one coherent straight, constant-pitch scope; normalize both source entries to pitch in millimetres, reversing only the normalized endpoints when an increasing TPI interval represents a decreasing pitch interval; divide one measured corresponding-point span by the exact whole number of pitch intervals; subtract the normalized source lower, upper and midpoint from measured pitch and report inclusive relation plus zero or positive nearest distance; convert measured pitch to TPI; multiply source pitch bounds and measured pitch by one independently sourced whole start count; and optionally subtract an independently reported same-scope lead without inventing a tolerance or approving anything
The exact standard/drawing edition, source-owned designation, pitch interval, measurement method/instrument/resolution/date, pitch-interval count, start-count source and reviewer must travel together. A nominal-only label, omitted pitch, guessed coarse/fine series, mixed revision, crest count mistaken for interval count, tapered/pipe thread, variable pitch or unknown start count requires another accountable source review and is refused.
Inside a source interval means only that the entered arithmetic agrees with those bounds. It does not identify the thread, verify a class or tolerance, establish major/minor/pitch diameters, approve fit or interchangeability, calculate thread strength, select a mating part or tap drill, or accept/disposition a manufactured part.
Keep measurement uncertainty and calibration, thread form and handedness, tolerances and gaging, fit/compatibility, workholding, cutting tool and machine setup, speed/feed/coolant, guarding, PPE, inspection plan, quality, rework, safety and work authorization with current exact standards, drawings, manufacturer instructions, controlled procedures and responsible qualified personnel.
Choose your path
Built around the job you need to finish
Compare one measured straight, constant-pitch thread with one accountable source pitch interval, normalize mm/in/TPI evidence, and derive lead only from an independently sourced whole start count while refusing identity, fit, machining, quality, disposition and safety decisions.
Manufacturing engineer reviewing a released drawing source
Reconcile one controlled pitch interval with a measurement record without allowing a nominal label or omitted pitch to become an invented thread specification.
Name one bounded straight-thread scope, retain the exact standard/drawing edition and source-owned designation, transcribe both pitch entries, then compare one documented span across an exact interval count.
Sees normalized pitch, TPI and signed source differences while class, tolerance, geometry, fit and any drawing disposition remain with the accountable engineering record.
Quality reviewer checking a pitch-span observation
Catch a unit, interval-count or transcription mismatch without treating arithmetic agreement as conformance or part acceptance.
Retain instrument, corresponding-point method, resolution, date and locator; enter the measured span and exact number of spaces between endpoints; inspect below/inside/above relation and nearest distance.
Receives reproducible comparison evidence while calibration, uncertainty, gaging, tolerance, inspection acceptance, rework and release stay external.
Maintenance specialist reconciling a multi-start lead record
Derive lead from observed pitch and an independently verified whole start count without choosing a replacement or authorizing machine work.
Add the start-count source, optionally enter an independent reported lead with its own locator, review the source-derived lead interval and signed residual, then retain or export a de-identified snapshot.
Can preserve pitch/lead arithmetic while handedness, compatibility, replacement selection, tooling, setup, guarding, PPE and work authorization remain with responsible procedures and people.
Authoritative checks for this tool
Outputs and checklists are planning aids. Review the linked current authorities and the records, terms, instructions, and requirements that apply to your exact situation before a consequential decision.
Measure between corresponding thread points and divide the span by the exact number of pitch intervals. The interval count is the number of spaces between the two endpoints, not the number of visible crests included.
Retain both source entries exactly as documented, then normalize them to millimetres. For TPI, a larger TPI value represents a smaller pitch, so the normalized pitch endpoints reverse before comparison.
Pitch (mm) = 25.4 ÷ TPI; TPI = 25.4 ÷ pitch (mm)
Lead from an explicit start count
Lead is derived only after an independent record supplies the exact whole number of thread starts. The resulting lead and optional reported-lead residual are arithmetic evidence, not thread identity, tolerance, fit or process approval.
Derived lead = measured pitch × thread-start count
Updated: September 2026
Example Scenarios
A manufacturing engineer transcribes one pitch interval from the current drawing, records the exact designation and revision, and compares a controlled span observation without asking the Tool to infer the thread class or any omitted value.
A quality reviewer records an instrument, corresponding-point method, resolution, date, measured span and exact interval count. The Tool exposes below, inside or above arithmetic relation while acceptance and disposition remain in the inspection plan.
A maintenance specialist retains an independent source for the whole start count, derives lead from measured pitch, and optionally compares an independently reported lead. Compatibility, replacement selection and machine work remain external.
Common Mistakes to Avoid
✕
Counting visible crests instead of pitch intervals
✓
Record two corresponding endpoints and count the spaces between them. A span containing eleven corresponding crest points contains ten pitch intervals; preserve the approved measurement method and evidence.
✕
Treating a nominal label or arithmetic match as thread identification
✓
Retain the complete source-owned designation, standard or drawing edition, class or tolerance when applicable, measurement evidence and start-count source. The Tool deliberately refuses to infer missing coarse/fine series, compatibility or conformance.
FAQ
Keep the exact standard, drawing or controlled-source revision; source-owned designation and pitch interval; instrument, method, resolution, date and span record; exact pitch-interval count; independently sourced start count; responsible reviewer; and explicit downstream decision boundary.
A longer documented span can make the arithmetic less sensitive to reading one tiny interval, but the Tool does not quantify measurement uncertainty. Use the approved instrument, calibration and method required by the responsible inspection process.
Each entered TPI endpoint is converted with pitch in millimetres equal to 25.4 divided by TPI. Because the relationship is inverse, the Tool orders the converted values into a lower-to-upper pitch interval before comparison.
No. Inside means only that the entered measured-pitch arithmetic falls between the entered source bounds. It does not verify identity, form, handedness, class, tolerance, diameter, measurement uncertainty, fit, compatibility or part acceptance.
No. Selection, dimensions, tolerances, gaging, fit, strength, tooling, workholding, speed, feed, coolant, guarding, PPE, quality disposition and work authorization require current exact sources and responsible qualified review outside this Tool.
About Thread Pitch and Lead Source Record
This record keeps source evidence, measurement evidence and arithmetic separate from thread identification. Enter one accountable pitch interval, measure a span across an exact number of pitch intervals, and retain the independent source for the whole thread-start count. The result reports normalized pitch, TPI, lead and signed differences only; it never fills in an omitted standard value or declares fit, conformance or safety.
