Convert between metric and inch thread designations — M, UNC, UNF, UNEF, BSP and NPT — showing pitch, diameters and the nearest equivalent where no exact match exists.
Complete reference tables and engineering data for metric-imperial thread. All values verified against ISO, ANSI, and manufacturer standards.
Published starting values are not measurements. They are recommendations, and they differ because each manufacturer optimises for something different — tool life, surface finish, chip control, or spindle power. Two suppliers can quote the same ISO grade and give you cutting speeds 30% apart, and each figure can be right for that supplier’s own geometry, edge preparation and coating.
That is why the number this calculator returns is a starting point, not a setting. Treat the catalogue figure as the middle of a band, then correct it on the first part: if the chips come off blue or the spindle load sits above roughly 80%, come down; if the finish is smeared and the chips are thin and stringy, come up. Write down what actually worked — that shop-specific number beats any published value.
Metric and imperial thread standards are not directly interchangeable — there is no exact conversion between M10 and any fractional inch thread. This reference helps you find the closest functional equivalents.
No, never. Thread profiles differ in flank angle (60° for both metric and UN, but 55° for BSW/BSP), crest and root geometry, and diameter-pitch relationship. Even a "close" fit is unsafe and will damage both threads.
M10×1.5 is dimensionally closest to 3/8-16 UNC in diameter (10 mm vs 9.525 mm). However, the pitch differs slightly (1.5 mm vs 1.588 mm/16 TPI). They are NOT interchangeable but serve similar applications.
North American oil & gas, aerospace legacy programs, and heavy equipment maintain imperial thread standards due to existing inventory, certification requirements, and regulatory constraints. NPT pipe threads remain dominant globally.
Use this reference table to find approximate equivalents between metric and imperial thread standards. For new designs, engineers often prefer metric coarse (ISO 724) for global compatibility. Always verify thread compatibility with the mating part before manufacturing.
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Use the calculator freely. If the result points to a tooling or process problem, we can source the exact carbide tooling you need from vetted factories in China. Compare factory-direct pricing.
Before you commit to a spec, it helps to know what the market pays for it. These are real, publicly listed factory prices — not a quotation, and not a guess.
We source the tool families below direct from vetted Chinese factories, matched to the material and tolerance you just worked out. Every batch ships with its material certificate and dimensional record.
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CONVERTING THREAD SYSTEMS? Mixing metric and imperial callouts is a common source of wrong goods. See how to write a tool specification that cannot be misread.
We source carbide cutting tools from China for job shops. We do not own a factory, which is why we can quote your drawing against two or three plants that actually run your material.
Cutting formulas with the units worked through · Speed and feed starting points for all six ISO material groups · How to read a carbide grade past its ISO code. 12 pages.
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