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ENEnglish繁中繁體中文ESEspañolARالعربيةFRFrançaisITItalianoPTPortuguêsRUРусскийDEDeutschJA日本語VITiếng ViệtKO한국어THไทยTRTürkçe

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Engineering Calculator · 111

Thread Diameter Taper Calculator

Calculate diameter taper and cone half-angle from two corresponding thread diameters and their axial separation.

Threads & entry geometry
Start calculationReview the method

Live calculation

Enter the known values.

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01

Inputs

02

Results

Diameter taper magnitude0.0625mm/mm
Diameter change per axial length6.25%
Absolute diameter change1.5mm
Cone half-angle1.7899°

Formula
k=∣D2−D1∣Lk=\frac{|D_2-D_1|}{L}α=arctan⁡(k2)\alpha=\arctan\left(\frac{k}{2}\right)

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Direct answer

What this result means

Diameter taper is the absolute difference between two corresponding diameters divided by their axial separation. A change of 1.5 mm over 24 mm gives 0.0625, equivalent to 1:16 diameter taper. This geometric check does not identify the thread standard or establish fit.

Thread Diameter Taper Calculator engineering relationship diagramThe two diameters must describe the same thread feature at separate axial stations. Diameter taper k uses the full diameter change; the cone half-angle α uses half that change. The diagram shows the two stations, axial length and inclined envelope, rather than thread flanks. This dedicated schematic represents thread diameter taper stations and is not to scale.D₁D₂LαAXIAL DIAMETER CHANGE · TOOL 111Diameter at station 1Diameter taper magnitude
Calculator-specific engineering relationship diagram — schematic, not a product drawing, and not to scale.

Formula & theory

Make the assumptions visible.

The two diameters must describe the same thread feature at separate axial stations. Diameter taper k uses the full diameter change; the cone half-angle α uses half that change. The diagram shows the two stations, axial length and inclined envelope, rather than thread flanks.

Calculation relationship
k=∣D2−D1∣Lk=\frac{|D_2-D_1|}{L}α=arctan⁡(k2)\alpha=\arctan\left(\frac{k}{2}\right)

The two diameters must describe the same thread feature at separate axial stations. Diameter taper k uses the full diameter change; the cone half-angle α uses half that change. The diagram shows the two stations, axial length and inclined envelope, rather than thread flanks.

Variables

D₂Corresponding diameter at the second axial stationmm
LAxial separation of the measurement stationsmm
kDiameter taper magnitude; 0.0625 corresponds to 1:16mm/mm
αHalf-angle between the cone envelope and its axis°

Use sequence

From measurement to review

  1. Record the same diameter characteristic at two defined axial stations.
  2. Enter both diameters and their positive axial separation in millimetres.
  3. Compare the geometric result with the specified thread drawing, tolerances and required gauges.

Limits

What this calculation does not confirm

  • Both measurements belong to one straight conical envelope; a parallel envelope returns zero taper.
  • Swapping the stations preserves taper magnitude. The sign or direction of taper must be recorded separately.
  • Pitch, flank angle, thread form, coating allowance and gauge acceptance require separate checks; this result is preliminary geometry.

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Calculator FAQ

Use the number without losing the engineering context.

These answers clarify what the tool calculates and where a product-specific review still begins.

01Calculator guidanceHow does a 1:16 diameter taper appear in these results?

A 1:16 diameter taper is 1 ÷ 16 = 0.0625 mm/mm, or 6.25% diameter change per axial length. Its cone half-angle is approximately 1.7899°. The result uses diameter taper rather than radius taper.

02Calculator guidanceIs the cone half-angle the thread flank angle?

No. The cone half-angle describes the slope of the overall tapered envelope relative to the axis. The flank angle describes the thread tooth profile, while the helix angle describes its helical path.

03Calculator guidanceCan measured taper distinguish NPT from BSPT?

Taper alone cannot distinguish them or prove interchangeability. Check the thread form, pitch, reference diameters, specified standard and acceptance gauges for the actual connection.

Product selection support

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Bepto Cable Glands can help relate a preliminary result to the product family and current model information for your application. You can start with the details you have; a complete drawing package is not needed to ask a question.

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