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What is Thread and Knurled Edge on a Metal Screw Cap?

  • Author:Edith
  • Source:www.xy-global.com
  • Release on:2018-01-23

A continuous threaded closure consists of a single continuous threading system that allows metal caps to be screw on to all different types of bottle and jars. Continuous thread caps are threaded with an unbroken thread inside the lid skirt, this is different than metal lug or twist caps, which are not threaded continuously. What does that mean? Continuous thread caps have a prominent thread on the side of the cap and ridges on the top.


Have you ever looked at a continuous threaded metal cap and wondered how all of those little cracks and crevices are made? It may seem tricky, but there are four pieces that make up a threaded metal closure; the top surface, knurl, thread roll, and wire.
A threaded metal closure begins at the top of the closure, the ridges on the metal cap are located around the top of the cap. These ridges are called knurls. Well, what is a knurl you may ask? A knurl is the indented or crimped portion on the skirt at the top of the cap, used for holding the liner in the cap. It is also used as a grip for removing the cap.   Below the knurl is the thread roll, the thread roll is what is used to twist and turn the metal closure onto the container (its one of the most important components, since it connects the cap to the closure.) Beneath the thread roll is the wire, the wire is the last portion of the metal cap, which is the bottom portion of the cap. The wire is one of the sharpest pieces on a metal cap before it is molded. It is the tubular structure formed at the open end of the metal closure that is formed into a smooth, strong surface.

While different manufacturer have different method, metal screw cap closure with this side wall finish is often referred as "thread and knurled edge" finish. So next time when you read "thread and knurled edge", it is simply referring to the side wall feature of the metal screw cap.