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Stub ACME Thread Calculator

Stub ACME threads are covered by ASME B1.8. For the general ACME form, see ACME (ASME B1.5).

Use this Stub ACME thread calculator to read rod (external) and nut (internal) limiting dimensions from the Stub ACME thread chart (ASME B1.8). Stub ACME has the same 29° thread angle as ACME, but a reduced thread height (≈ 0.3P) for shallow threads.

Tip: If you are comparing general ACME vs stub ACME, use the calculators on this page and the linked pages below to avoid mixing standards.

Inputs

Filters the size dropdown list.
This page is for single‑start stub ACME chart values.
mm = inch × 25.4
Example buttons load a common size if it exists in the table.

What is calculated

  • External (rod): major diameter (max/min), pitch diameter (max/min), minor diameter (max/min).
  • Internal (nut): major diameter (max/min), pitch diameter (max/min), minor diameter (max/min).
  • Basic values: pitch P = 1/TPI, basic pitch diameter D2 = D − 0.5P, basic minor diameter D1 = D − P.

Thread angle is 29°. h ≈ 0.3P (stub ACME).

Results

Designation: —

External thread (rod)

Limits Max / Min / Tol
Diameter Max Min Tol
Major — — —
Pitch — — —
Minor — — —

Internal thread (nut)

Limits Max / Min / Tol
Diameter Max Min Tol
Major — — —
Pitch — — —
Minor — — —

Basic values

Basics Derived from size + TPI
TPI—
Pitch (P)—
Basic major (D)—
Basic pitch dia (D2)—
Basic minor dia (D1)—
Lead angle—
Lead (L)—

Notes

—

Searchable Stub ACME thread chart

This table is generated from the same lookup data used by the calculator.

Size TPI Class Major diameter Pitch diameter Minor diameter
Max Min Max Min Max Min
Showing 0 rows.

ACME vs Stub ACME and tolerance classes

General‑purpose ACME (ASME B1.5) commonly uses class 2G. Choose 3G or 4G when you need a tighter fit and less backlash. Stub ACME (ASME B1.8) uses a shallower thread form and is used when you need a coarse pitch with reduced thread depth.

How to use this calculator

  1. Select a thread size (diameter–TPI).
  2. Select tolerance class.
  3. For general ACME, choose the number of starts if you have a multi‑start lead screw.
  4. Read the rod/nut limits, then compare min/max clearance at the pitch diameter if needed.

Related tools

Reference

ASME/ANSI B1.8 (Stub ACME Screw Threads) and Machinery’s Handbook.

What is a Stub ACME thread?

A Stub ACME thread is a 29° trapezoidal ACME form with reduced thread height. The stub form is used where wall thickness is limited or where a shallower thread is preferred while keeping the ACME flank angle.

Stub ACME vs General ACME

FeatureStub ACMEGeneral ACME
StandardASME B1.8ASME B1.5
Included angle29°29°
Thread heightReduced (stub form)Higher (general form)
Typical useThin-wall / limited depthGeneral power screws
Need general ACME values? Use the General ACME calculator.

Stub ACME profile and formulas

This page shows limiting dimensions from embedded ASME B1.8 tables. Helpful basics: P (pitch), n (TPI) and the basic diameters. Stub ACME uses a reduced thread height compared with general ACME.

  • P = 1 / TPI
  • Major diameter, pitch diameter and minor diameter limits are taken from ASME B1.8 tables for the selected size.

Tolerances (Stub ACME)

Stub ACME dimensions on this page follow ASME B1.8 table values. Use the internal and external limits to determine clearance, engagement and machining targets for nuts and screws.

FAQ

Which standard defines Stub ACME threads?

Stub ACME thread dimensions are defined in ASME/ANSI B1.8.

Why use Stub ACME instead of general ACME?

Stub ACME is often selected when there is limited wall thickness or thread depth, while still using the 29° ACME flank angle.

Can I use this page for internal and external threads?

Yes. Select a size to view both external (rod) and internal (nut) limiting dimensions.