Undercut manufacturing

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In manufacturing, an undercut is a special type of recessed surface. In turning it refers to a recess in a diameter. In machining it refers to a recess in a corner. In molding it refers to a feature that cannot be molded using only a single pull mold. In printed circuit board construction it refers to the portion of the wafer that is etched away under the photoresist. For more information on manufacturers and suppliers, please refer to this guide China Export Suppliers.


Turning


On turned parts an undercut is also known as a neck. They are often used at the end of the threaded portion of a shaft or screw to provide clearance for the cutting tool. For proper usage the undercut should be at least 1.5 threads long and the diameter should be at least 0.015 in (0.38 mm) smaller than the minor diameter of the thread.

They are also often used on shafts that have diameter changes so that a mating part can seat against the shoulder. If an undercut is not provided there is always a small radius left behind even if a sharp corner is intended. These types of undercuts are called out on technical drawings by stating the width and either the depth or the diameter of the bottom of the neck


Etching


Undercuts from etching are somewhat different than the undercuts explained above, because it is a side effect, not an intentional feature. Undercuts from etching can occur from two common causes. The first is over etching, which means the etchant was applied too long. The second is due to an isotropic etchant, which means the etchant etches in all directions equally. To overcome this problem an anisotropic etchant is used



Reference:

1. http://en.wikipedia.org/wiki/Undercut_(manufacturing)


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