The size measurement of aluminum caps is a precise task that requires measuring multiple key dimensions to ensure their perfect fit and sealing performance with the bottle mouth. The following is a detailed explanation for measuring the size of aluminum covers:
Core components of aluminum cover size measurement
The size system of aluminum covers is similar to that of plastic covers, but due to the special nature of their material (metal) and processing technology (stamping, rolling), there is a focus on measurement.
1. Diameter Dimensions
This is the most critical set of dimensions that directly affect the sealing and screwing functions.
Outer Diameter (O.D.):
Definition: The diameter of the outermost edge of the aluminum cover skirt.
Measuring tool: digital caliper or specialized gauge.
Importance: Affects the appearance and visual coordination with the bottle body.
Thread Inner Diameter/Pitch Diameter:
Definition: This is the reference diameter of the internal thread of the aluminum cap, which is the most essential collaborative dimension.
Measuring tool: Thread Plug Gauge is the standard and most accurate method. The through end (T) must be smoothly screwed in, and the stop end (Z) cannot be screwed in or screwed in no more than the specified number of turns, in order to determine whether the tooth diameter and pitch are qualified.
Importance: It must be perfectly matched with the external thread diameter of the bottle mouth. This size is also commonly used in the industry to refer to aluminum covers, such as the "28mm ROPP cover".
Sealing Inner Diameter:
Definition: The diameter of the contact area between the inner part of the bottle cap and the top plane of the bottle mouth (for flat gasket sealing), or the diameter of the inner stopper structure (if any).
Measuring tool: caliper or projector.
Importance: It determines the compression area and sealing effect of the liner.
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