BIZOMAT MAKEOS · Threads
Unified Inch Thread Basic Dimensions
What are the basic pitch and minor diameters and stress area of this UNC or UNF thread?
Basic dimensions of a Unified (UN/UNR) inch thread from its major diameter and threads per inch, in inches and millimetres.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Basic major diameter | in | Nominal size in inches (e.g. 0.5 for ½-13 UNC). |
| Threads per inch | TPI | Threads per inch from the designation. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Basic major diameter
- What it is
- The basic major diameter of the unified inch thread in decimal inches: the size before the dash in the designation, written as a decimal.
- Units and format
- Enter a number in in: inches. The form accepts 0.000001 in to 40 in. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.5 in as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Enter numbered sizes (such as No. 10) as their decimal diameter, and fractions as decimals.
What this means: Threads per inch
- What it is
- The number of thread crests per inch of length: the number after the dash in the designation. The pitch is one inch divided by this number.
- Units and format
- Enter a number in TPI: threads per inch. The form accepts 0.000001 TPI to 200 TPI. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 13 TPI as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- More threads per inch give a finer pitch and larger pitch and minor diameters.
- Get it right
- Check the series: UNC and UNF threads of the same size have different counts.
Method and formulas
- Pitch = 1 ÷ n; H = 0.866025 ÷ n.
- Basic pitch diameter E = D − 0.649519 ÷ n; basic minor (internal) = D − 1.082532 ÷ n.
- Tensile stress area At = 0.7854 (D − 0.9743 ÷ n)².
- Example: 0.5-13 UNC has E = 0.45004 in and At = 0.1419 in².
Limitations
- Basic profile only; class 2A/2B and 3A/3B limits come from ASME B1.1 tables.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check inch thread dimensions for design or inspection
- Find the stress area for an inch bolt
- Convert inch thread data to metric
Who it is for
- Design engineers
- Machinists
- Quality inspectors
What you get
- Pitch
- Basic pitch diameter
- Basic minor diameter (internal)
- Tensile stress area
Interpreting the result
- Use the stress area for bolt stress calculations.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1806–1866. Topic reference; no source tables or recommended settings are reproduced.
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