Finish identifiers select a complete drawing
PCO and PCF finish numbers identify particular neck interfaces. A nominal diameter alone does not identify the pitch, number of starts, sealing bore, tamper bead or support ledge. The finish selector keeps each drawing separate.
Pitch and lead
Pitch is the axial spacing between adjacent thread starts. Lead is travel in one complete revolution. Some drawings print both independently rounded values; the calculator preserves both. It derives one from the other only when the source identifies the quantity and the number of starts. Thread interruptions and the full-depth angular extent remain separate constraints.
Seal and parting-line dimensions
Inside sealing diameters may be controlled at particular depths, or chosen by the container manufacturer. F and G can describe opposite sides of a parting-line interface. An unknown nominal diameter remains unknown even when the drawing gives a tolerance around the manufacturer's chosen nominal.
What the datum plot shows
The plot locates identified diameter and height callouts with equal horizontal and vertical physical scale. PCO 1881 and PCF-38P-1 also include a separately enlarged, source-defined local thread section with tangent circular blends. The local section excludes start blends, vent interruptions and thread ends. Other finishes show dimension datums without inferring a contour. A complete seal, support-ring or helical surface cannot be inferred from these views. The tables retain the other published radii, angles, limits and construction notes; full construction can require the source's CAD model and closure drawing.
Source basis
Millimetre and inch values are retained as separately printed sets. Choose a source basis before changing display units. Parenthesized references, basic dimensions, asymmetric tolerances and minimum/maximum limits preserve their source qualification. A source conflict is identified in the finish notes.