Neck & Thread Geometry

Estimate bottle neck and thread dimensions for caps and closures.

Preset Neck outer diameter (mm) Neck wall thickness (mm) Thread starts Thread pitch (mm) Thread depth (mm) Thread turns Seal land length (mm) Cap internal minor diameter (mm) Cap thread length (mm) Thread form angle (°)

Core dia = OD - 2*depth. Thread length = pitch * starts * turns.

Neck core (minor) diameter: —

Thread length: —

Helix (lead) angle: —

Total neck length (est.): —

Cap engagement check

Radial clearance: —

Effective engagement length: —

—

Minimum engagement ≈ 1.5 × pitch. Verify against the closure specification.

Cap internal thread (from form angle)

Closure nominal diameter (mm)

Cap internal thread major/pitch/minor diameters from nominal, pitch and form angle (symmetric V model).

Cap thread major (crest) dia.: —

Cap thread pitch dia.: —

Cap thread minor (root) dia.: —

Cap thread depth (radial): —

Theoretical thread engagement height

Theoretical thread height (form angle): —

Neck thread vs form: —

Cap thread vs form: —

Radial engagement height: —

Bore clearance (cap major − neck OD): —

—

Theoretical thread height = pitch / (2·tan(form angle/2)); practical (truncated) depth = 1.25× that. Check the neck thread form is sufficiently complete and the cap bore clears the neck OD before production.

Joint engagement check (radial height + axial length)

Radial engagement height (form angle): —

Axial engagement length (min of threads): —

Min. axial engagement (1.5× pitch): —

Effective axial engagement (flank): —

—

Passes only when the radial thread height (form-angle completeness and bore clearance) AND the axial engagement length are both sufficient. If either is short the joint is warn; if the cap bore is smaller than the neck OD it is fail. Representative geometry — verify against the closure specification.