Undercut (manufacturing)

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In manufacturing, an undercut is a special type of recessed surface that is inaccessible using a straight tool. In turning, it refers to a recess in a diameter generally on the inside diameter of the part. In milling, it refers to a feature which is not visible when the part is viewed from the spindle. 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 copper that is etched away under the photoresist.



An example of a turned part with and without an undercut Undercut turning.png
An example of a turned part with and without an undercut

On turned parts an undercut is also known as a neck or "relief groove". They are often used at the end of the threaded portion of a shaft or screw to provide clearance for the cutting tool.


A simple example of molding an external undercut Ondersnijding.gif
A simple example of molding an external undercut

Undercut - Any indentation or protrusion in a shape that will prevent its withdrawal from a one-piece mold.


Top and Front view of a milled undercut slot Milled undercut slot example.jpg
Top and Front view of a milled undercut slot

In milling the spindle is where a cutting tool is mounted. In some situations material must be cut from a direction where the feature can not be seen from the perspective of the spindle and requires special tooling to reach behind the visible material.

An example of a machining undercut Undercut machining.png
An example of a machining undercut

The corners may be undercut to remove the radius that is usually left by the milling cutter this is commonly referred to as a relief.


Undercuts from etching (microfabrication) are a side effect, not an intentional feature.


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Drilling Cutting process that uses a drill bit to cut a hole of circular cross-section in solid materials

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A countersink is a conical hole cut into a manufactured object, or the cutter used to cut such a hole. A common use is to allow the head of a countersunk bolt, screw or rivet, when placed in the hole, to sit flush with or below the surface of the surrounding material. A countersink may also be used to remove the burr left from a drilling or tapping operation thereby improving the finish of the product and removing any hazardous sharp edges.

Machine taper

A machine taper is a system for securing cutting tools or toolholders in the spindle of a machine tool or power tool. A male member of conical form fits into the female socket, which has a matching taper of equal angle.

Grinding wheel

Grinding wheels contains abrasive compounds for grinding and abrasive machining operations. Such wheels are also used in grinding machines.

Milling cutters are cutting tools typically used in milling machines or machining centres to perform milling operations. They remove material by their movement within the machine or directly from the cutter's shape.

Metal lathe

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End mill

An end mill is a type of milling cutter, a cutting tool used in industrial milling applications. It is distinguished from the drill bit in its application, geometry, and manufacture. While a drill bit can only cut in the axial direction, most milling bits can cut in the radial direction. Not all mills can cut axially; those designed to cut axially are known as end mills.

Boring (manufacturing)

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Grinding (abrasive cutting)

Grinding is a type of abrasive machining process which uses a grinding wheel as cutting tool.


A spotface or spot face is a machined feature in which a certain region of the workpiece is faced, providing a smooth, flat, accurately located surface. This is especially relevant on workpieces cast or forged, where the spotface's smooth, flat, accurately located surface stands in distinction to the surrounding surface whose roughness, flatness, and location are subject to wider tolerances and thus not assured with a machining level of precision. The most common application of spotfacing is facing the area around a bolt hole where the bolt's head will sit, which is often done by cutting a shallow counterbore, just deep enough "to clean up"—that is, only enough material is removed to get down past any irregularity and thus make the surface flat. Other common applications of spotfacing involve facing a pad onto a boss, creating planar surfaces in known locations that can orient a casting or forging into position in the assembly; allow part marking such as stamping or nameplate riveting; or offer machine-finish visual appeal in spots, without the need for finishing all over (FAO).

Threading is the process of creating a screw thread. More screw threads are produced each year than any other machine element. There are many methods of generating threads, including subtractive methods ; deformative or transformative methods ; additive methods ; or combinations thereof.

Milling (machining) Removal of material from a workpiece using rotating tools

Milling is the process of machining using rotary cutters to remove material by advancing a cutter into a workpiece. This may be done varying direction on one or several axes, cutter head speed, and pressure. Milling covers a wide variety of different operations and machines, on scales from small individual parts to large, heavy-duty gang milling operations. It is one of the most commonly used processes for machining custom parts to precise tolerances.

Undercut (turning)

In turning, an undercut is a recess in a diameter generally on the inside diameter of the part.