The Finish Dimensions test is designed to ensure that all thread finishes on bottles or preforms comply with the dimensions and allowable tolerances specified on the respective bottle finish design drawings. In addition, there shall be no continuous or excessive flash, and no overhang between the F and G dimensions.
The laboratory should consult with the customer or bottle supplier (if the bottle supplier is not the customer) to ensure that copies of the most recent drawings are available for each finish that is specified for use with the bottles to be measured.
Using an optical comparator of at least 20X magnification or a vision system, the following dimensions are typically evaluated, designations and descriptions are per ISBT:
T: Thread crest diameter
E: Thread root diameter
A: Tamper evident bead diameter
C: Control diameter (ID) at TOF (Top of finish)
H: Clearance height required for proper closure function
D: Tamper evident bead height measured from TOF to gauge pt
X: Height from TOF to bottom of support ledge