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Engineering Calculator · 130

ISO Metric Basic Thread Diameter Calculator

Calculate ISO metric 60° basic-profile pitch diameter, internal minor diameter and fundamental triangle height from nominal major diameter and pitch.

Threads & entry geometry
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Live calculation

Enter the known values.

Units remain visible beside every field and result. Change any input to recalculate immediately in your browser.

01

Inputs

02

Results

Basic pitch diameter d₂ / D₂19.025721mm
Basic internal minor diameter D₁18.376202mm
Fundamental triangle height H1.299038mm
Basic radial engagement height 5H/80.811899mm

Formula
H=32PH=\frac{\sqrt{3}}{2}Pd2=D2=d−34Hd_2=D_2=d-\frac{3}{4}HD1=d−54HD_1=d-\frac{5}{4}H

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Direct answer

What this result means

For the metric 60° basic profile, H = √3P/2, pitch diameter is d − 3H/4 and basic internal minor diameter is d − 5H/4. With nominal diameter 20 mm and pitch 1.5 mm, these give 19.0257 mm and 18.3762 mm. They are basic geometry, not measured thread limits or acceptance gauges.

ISO Metric Basic Thread Diameter Calculator engineering relationship diagramThe nominal major diameter and axial pitch define this 60° basic profile. D1 is explicitly the basic internal minor diameter. A manufactured external root, including a rounded-root design diameter, is a separate quantity; do not rename D1 as that external root or use basic dimensions as tolerance limits. This dedicated schematic represents metric basic pitch internal minor profile and is not to scale.Pitch P60°dd₂Internal D₁H60° BASIC PROFILE GEOMETRY · TOOL 130Nominal basic major diamet…Basic pitch diameter d₂ / …
Calculator-specific engineering relationship diagram — schematic, not a product drawing, and not to scale.

Formula & theory

Make the assumptions visible.

The nominal major diameter and axial pitch define this 60° basic profile. D1 is explicitly the basic internal minor diameter. A manufactured external root, including a rounded-root design diameter, is a separate quantity; do not rename D1 as that external root or use basic dimensions as tolerance limits.

Calculation relationship
H=32PH=\frac{\sqrt{3}}{2}Pd2=D2=d−34Hd_2=D_2=d-\frac{3}{4}HD1=d−54HD_1=d-\frac{5}{4}H

The nominal major diameter and axial pitch define this 60° basic profile. D1 is explicitly the basic internal minor diameter. A manufactured external root, including a rounded-root design diameter, is a separate quantity; do not rename D1 as that external root or use basic dimensions as tolerance limits.

Formula terms

Variables

Use sequence

From measurement to review

  1. Confirm the thread is a specified ISO metric 60° profile and obtain its nominal diameter and pitch.
  2. Enter those dimensions and distinguish the calculated basic pitch and internal minor diameters.
  3. Apply the actual tolerance class, root design, coating allowance and gauging requirements separately before assessing fit.

Limits

What this calculation does not confirm

  • The result applies to the metric 60° basic profile, not NPT, PG, trapezoidal or other thread forms.
  • The calculated minor diameter is internal D1. External rounded-root design diameter and actual manufactured root limits are excluded.
  • Preferred size selection, tolerances, coating, engagement strength and gauge acceptance are not determined; these dimensions are preliminary reference 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 guidanceWhich minor diameter does this metric tool return?

It returns basic internal minor diameter D1 = d − 5H/4. It does not return a manufactured external rounded-root diameter or the maximum/minimum dimensions of a tolerance class.

02Calculator guidanceCan these basic metric diameters establish thread fit or a drilling size?

No. Fit requires the specified tolerance classes and gauges, and a drilling or tapping process also depends on the material, tooling and process specification. Basic dimensions alone do not select those limits.

03Calculator guidanceWhy must this 60° metric calculation not be applied to NPT or PG threads?

Those systems have their own profiles, dimensions, taper or flank geometry and gauging rules. Entering their nominal labels into this metric basic-profile equation would produce an unrelated geometry.

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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