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Neck Finish Inspection:

A table of common industry-standard Neck Finish terms and definitions

"E" Dimension

The outside diameter of neck on a threaded bottle neck (finish). The diameter of the neck (finish) is measured across the root of the threads.

"H" Dimension

The height of the bottle finish measured from the sealing surface, in a line parallel to the axis of the finish and tangent to the threads on the finish, down to a point where the line intersects the body (shoulder) of the container. The inside height of the closure measured from the bottom of the closure, in a line tangent to the threads of the closure and terminating at the inside, top of closure.

"I" Dimension

A specified minimum diameter inside the bottle neck. A minimum diameter is specified to allow sufficient clearance for filling tubes to enter the bottle neck easily.

"L" Dimension

The vertical distance from the sealing surface to the top part of neck bead, i.e., where the uppermost part of the bead intersects the container neck.

"L" Style Thread

A type of thread contour (cross-section) roughly trapezoidal in outline. The outermost part is radiussed a "general purpose" thread contour designed for use with metal or plastic closures.

"S" Dimension

Locates the position of the bottle thread with respect to the sealing surface. The "S" dimension is the vertical distance from the sealing surface to the intersection of the finish wall and the top part of the first part of bottle thread where full depth contour exists.

"T" Dimension

The outside diameter of the thread helix on a bottle finish.

These are common industry designators for dimensions on the threaded neck of common plastic bottle. (e.g., beverage container, cough syrup, plastic motor oil bottle) These dimensions are typically measured in silhouette or from a perch above the conveyor as the product passes.

Applications in the field are numerous but there are a great many common concerns for manufacturers which make the above dimensions important.

  1. ease of threading a cap at high speed with automated equipment
  2. quality of pressure/vacuum seal with the cap
  3. inner diameter of the neck to facilitate high speed filling
  4. quality of the thread for cap torque.

Apart from the dimensions enumerated above, the flatness of the sealing surface is important for sealing. Gouges, uneven mold-halves, bubbles, etc., can open up leak paths that are almost always impermissible.