ISO 4014 Hex Bolt Dimensions

What's the difference between ISO 4014 and ISO 4017?

ISO 4014 standardizes partial-thread hex bolts: at short and medium lengths a defined smooth shank section remains between the head and the start of the thread. Thread length b is fixed per nominal diameter independent of overall length -- it grows only in three steps with length (up to 125 mm, 125-200 mm, above 200 mm), not continuously. If the chosen overall length is shorter than this thread length, the thread reaches under the head -- the bolt is then, by definition, no longer an ISO 4014 bolt but an ISO 4017 one.

Formula and variables

A pure table lookup from Table 2 (M5-M12) and Table 3 (M14-M24) of the standard. Thread length b follows the relation confirmed in both tables, b=2d+6 (l≤125 mm), b=2d+12 (125<l≤200 mm) or b=2d+25 (l>200 mm); all other dimensions are tabulated directly.

Choose the inputs correctly

Nominal size (M5 to M24, product class A) and nominal length l under the head.

How to use the calculator

Enter nominal size and the desired overall length. The calculator flags when the length is too short for a partial-thread bolt -- ISO 4017 then applies instead.

Worked example

M10x60: width across flats s=16.00 mm, head height k=6.4 mm, thread length b=26 mm, so up to 34 mm of smooth shank by calculation.

How reliable is the shown shank length?

Thread length b is an exact standard value. The smooth shank length derived from it (l−b) is instead a calculated upper bound, not a tabulated standard minimum: ISO 4014 additionally gives a more finely stepped minimum shank length ls,min per standard length in Table 2/3, which is somewhat smaller than l−b because of the thread run-out. For non-critical applications l−b is a usable approximation; for shear pins, close fits or tightly toleranced clamped lengths, consult the exact ls,min column of the printed table.

All dimensions in millimetres.

Typical applications

CAD design of bolted joints, determining available clamp or shear length, selecting the correct tool size (width across flats) for assembly.

Assumptions, limits and common mistakes

ISO 4014:2022 (DIN EN ISO 4014:2022-10), Tables 2 and 3.

Common mistake: Don't equate the nominal diameter with the actual shank diameter -- ds,max equals the nominal size, ds,min lies below it (for M10: 9.78 instead of 10.00 mm). For close fits, ds,min governs, not the nominal diameter.