Calculate basic dimensions, tolerances, and limits of metric threads.
Calculate basic diameters, pitch diameter and tolerance limits for coarse or fine metric threads.
Thread designation, nominal diameter, pitch and internal/external tolerance position and grade define the geometry. Example: M12×1.75–6H/6g.
Pitch sets flank geometry, minor diameter and axial advance. Internal and external classes must be compatible; a finer pitch increases self-locking but leaves less tolerance per thread.
The 60° profile and pitch yield d₂/d₃ or D₂/D₁. The tolerance class shifts and widens the limit dimensions.
M12×1.75–6H/6g means internal class 6H and external class 6g with the coarse 1.75 mm pitch, a common general-purpose starting point.
Sources and limits: ISO 261 defines thread series, ISO 724 the basic profile and ISO 965 tolerances. Strength and engagement length are separate checks.
Calculate basic diameters, pitch diameter and tolerance limits for coarse or fine metric threads.
Bolt calculations describe a joint through geometry, preload, friction and material limits. Preload clamps the parts; external load, embedding and temperature change the reserve.
The 60° profile and pitch yield d₂/d₃ or D₂/D₁. The tolerance class shifts and widens the limit dimensions.
Thread designation, nominal diameter, pitch and internal/external tolerance position and grade define the geometry. Example: M12×1.75–6H/6g. Pitch sets flank geometry, minor diameter and axial advance. Internal and external classes must be compatible; a finer pitch increases self-locking but leaves less tolerance per thread.
Enter nominal diameter and pitch (or pick a designation such as M12×1.75) plus the desired tolerance position and grade for internal and external threads. The calculator returns pitch, minor and other limit dimensions separately for both thread parts.
M12×1.75–6H/6g means internal class 6H and external class 6g with the coarse 1.75 mm pitch, a common general-purpose starting point.
Pitch sets flank geometry, minor diameter and axial advance. Internal and external classes must be compatible; a finer pitch increases self-locking but leaves less tolerance per thread. A passing result means only that the selected model stays within the entered limits. Tightening scatter and real contact surfaces may govern residual clamp force.
Diameter and pitch in millimetres; tolerance position as a letter (e.g. H, g) and grade as a number (e.g. 6H, 6g) per ISO 965.
Looking up limit dimensions for shop drawings, selecting gauging equipment (thread gauges), or checking whether an internal and external thread from different sources actually mate.
ISO 261 defines thread series, ISO 724 the basic profile and ISO 965 tolerances. Strength and engagement length are separate checks.
Common mistake: Don't confuse coarse and fine pitch threads of the same nominal size – they have different pitch, minor and pitch diameters. Uppercase and lowercase tolerance letters are fixed: uppercase (e.g. H) is always internal thread, lowercase (e.g. g) always external – swapping them gives an invalid pairing.
6 is the tolerance grade (tolerance-band width), H and g the tolerance position. 6H describes an internal thread with fundamental deviation H (no allowance), 6g an external thread with a small deviation g.
Nominal diameter names only the external thread's outside diameter. Pitch and minor diameter follow from the 60° basic profile and pitch, and govern the load-bearing thread area.
No. It gives only geometry. Tensile stress, preload and tightening torque are found with the dedicated bolt calculators, which build on the same tensile stress area Aₛ.
Thread size, pitch, and tolerance classes produce basic dimensions, limit sizes, and pitch-diameter clearance.
Basic and limit dimensions support design and inspection. Engagement length, coating, gauging, and the actual fastener product remain separate decisions.
Choose diameter and pitch from ISO 261 where possible; special combinations complicate sourcing and inspection.
The usual tolerance class assumes an appropriate engagement-length group.
Electroplated or other coatings require a coordinated allowance and inspection concept.
Gauges and gauging for ISO metric screw threads.
Basic profile underlying ISO metric geometry.
Mechanical properties for steel or stainless fasteners.