Notching
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Notching is a metal-cutting process used on sheet-metal or thin bar-stock, sometimes on angle sections or tube. A shearing or
punching Punching is a forming process that uses a punch press to force a tool, called a '' punch'', through the workpiece to create a hole via shearing. Punching is applicable to a wide variety of materials that come in sheet form, including sheet me ...
process is used in a press, so as to cut vertically down and perpendicular to the surface, working from the edge of a work-piece. Sometimes the goal is merely the notch itself, but usually this is a precursor to some other process: such as bending a corner in sheet or joining two tubes at a tee joint, notching one to fit closely to the other. Notching is a low-cost process, particularly for its low tooling costs with a small range of standard punches. The capital cost of the
punch press A punch press is a type of machine press used to cut holes in material. It can be small and manually operated and hold one simple die (manufacturing), die set, or be very large, CNC operated, with a multi-station turret and hold a much larger and c ...
can be expensive though, so small fabrication shops often out-source their notching work to a press shop or notching specialist. Notching of large or heavy sections, particularly for large tube fabrication or
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, is increasingly carried out by plasma-cutting rather than punch tools. The first punch & die type tool for notching tube & pipe was invented in
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by Julius Vogel, who was issued a US patent in 1938. The accuracy of punch notching is good, depending on the care with which it's carried out. For manual folding work, prior notching can often improve resultant accuracy of the folding itself. The speed of notching is usually limited by manual handling when loading the workpieces into the press. Pieces some feet long may be manually loaded into a single-stroke press. Smaller pieces are still generally hand-fed, limiting speeds to perhaps 100 strokes / minute. Almost any workable metal can be notched. It's particularly suitable where the metal is otherwise awkward to drill, such as stainless steels, titanium or previously heat-treated aluminium alloys. It is an operation of removing a small part of
metal sheet Sheet metal is metal formed into thin, flat pieces, usually by an industrial process. Thicknesses can vary significantly; extremely thin sheets are considered foil or leaf, and pieces thicker than 6 mm (0.25 in) are considered plate, ...
of desired shape from edge of metal sheet.


Tube notching

Tube notching is commonly performed before joining light-gauge tubes to make a tee or similar joint, as by welding. Either one or both tubes may be notched before assembly. A familiar example of tube notching is in the manufacture of
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s. End notching works the ''end'' of the tube, such as a semicircular concavity to make the base of a tee, or a convex vee to fit into a mitre. Side notching (also called offset notching) works the ''side'' of a tube with a vee notch for bending, semicircular or vee notches for tee joint. Tube being hollow, it's not practical to use a simple punch operation to notch it, as it would be squashed. Although punching is possible, it requires support mandrels and awkward handling. Where tube is worked with a punch press other than for side notching, this is generally described as ''slotting''. Tube notching for fabrication of circular tube is thus most commonly done with a rotary
hole saw A hole saw (also styled holesaw), also known as a hole cutter, is a saw blade of annular (ring) shape, whose annular kerf creates a hole in the workpiece without having to cut up the core material. It is used in a drill. Hole saws typically ha ...
in which a hole saw of the diameter of the tube being attached to is fed into the stock to be notched at a semi-perpendicular angle. This produces a semi-circular notch. Rather than using large presses, such saw notching may only require a simple jig, also making it suitable for on-site working. A much more accurate way of notching the end of tube stock is to use a specially made
milling cutter Milling cutters are cutting tools typically used in milling machines or machining centres to perform milling operations (and occasionally in other machine tools). They remove material by their movement within the machine (e.g., a ball nose mill) ...
called an
end mill An end mill is a type of milling cutter, a cutting tool used in industrial milling applications. They can have several end configurations: round (ball), tapered, or straight are a few popular types. They are most commonly used in "milling machi ...
. The stock to be notched is clamped into a
vise A vise or vice (British English) is a mechanical apparatus used to secure an object to allow work to be performed on it. Vises have two parallel jaws, one fixed and the other movable, threaded in and out by a screw and lever. The jaws are ofte ...
and can then be fed slowly and accurately into a rotating, hardened metal, end mill. This method requires more expensive equipment and lacks the portability of the hole saw method, as the machine is typically bolted for stability and safety. This method of end notching is much faster and thus greatly minimizes the chance of damaging the stock either by warping due to heat build up or by squashing as can still happen with a hole saw. Notching in thin-wall tube may also be carried out by abrasive tools, reducing some of the risk of damage from a hole saw snatching. This also allows more complex shapes to be performed, such as vee notches. In some cases, a helical end mill cutter may be used.
Computer numerical control Computer numerical control (CNC) or CNC machining is the Automation, automated control of machine tools by a computer. It is an evolution of numerical control (NC), where machine tools are directly managed by data storage media such as punched ...
(CNC) notching is enabling designers to work with more complex geometries.


Notch and bend

Vee notches in tube, particularly square tube, may be cut so deep as to cut almost through the tube: three sides of a square tube. This then allows torner, usually finished by welding. On a smaller scale for
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, this operation is performed by hand-filing precious-metal strip before bending and soldering to make box frames or stone mounts.


References

{{reflist Fabrication (metal)