Machining Metal Removal

Machining metal removal is the process of shaping, cutting, or removing material from a workpiece to achieve the desired shape, size, and surface finish.  This process is widely used in manufacturing and metalworking industries to create a wide range of products, from simple components to complex parts.  The primary goal of machining metal removal is to remove excess material, refine the workpiece's dimensions, and improve its surface quality.

Key Points about Machining Metal Removal

Turning  -  Turning involves rotating a workpiece on a lathe while a cutting tool removes material from the workpiece's outer surface.  This process is commonly used for cylindrical parts like shafts and spindles.
Milling  -  Milling uses rotary cutters to remove material from a workpiece.  The cutter can move along multiple axes, allowing for the creation of various shapes, slots, and contours.  Milling machines are versatile and used for both simple and complex parts.
Drilling  -  Drilling is the process of creating holes in a workpiece using a rotating cutting tool called a drill bit.  It is a common operation for creating holes in metal components.
Grinding  -  Grinding is used to achieve fine surface finishes and tight tolerances.  It involves abrasive wheels that remove material by grinding or abrasion.  This process is ideal for achieving precise dimensions and smooth surfaces.
Electrical Discharge Machining (EDM)  -  EDM utilizes electrical sparks to erode the workpiece material.  It is suitable for machining intricate shapes and hardened materials that are difficult to machine with traditional methods.
Wire EDM  -  This is a variation of EDM where a thin, electrically charged wire is used to cut through the workpiece, creating complex shapes with high precision.
Abrasive Water Jet Cutting  -  In this method, a high-pressure stream of water mixed with abrasive particles is used to cut through metal.  It is suitable for cutting various materials, including metals, plastics, and composites.
Laser Cutting  -  Laser cutting employs a high-energy laser beam to melt, burn, or vaporize material from the workpiece.  It is used for precise and fast cutting of thin to thick metal sheets.
Plasma Cutting  -  Plasma cutting uses a high temperature, ionized gas (plasma) to melt and remove material from a workpiece.  It is commonly used for cutting thick metal plates and is often employed in industrial applications.

Each of these machining processes has its advantages and limitations, making them suitable for different applications.  The choice of method depends on factors such as the material being machined, the desired tolerances, surface finish, production volume, and the complexity of the part being manufactured.  Machining metal removal is a crucial step in the production of a wide range of products across various industries, including automotive, aerospace, electronics, and more.

Machining Variables / Abbreviations
Symbol	Meaning	English	Metric
\(CT\)  =  Chip Thickness	The thickness of each chip cut by a tool, measured at its latgest cross-section.	\(in\)	\(mm\)
\(CF\)  =  Cutting Feed	The distance that the cutting tool advances during one revolution of the workpiece or per unit of time. (\(FR\) = Feed Rate)	\(in\;/\;rev\)	\(mm\;/\;rev\)
\(C_f\)  =  Cutting Force	The force a cutting tool exerts on a workpiece during machining, and the resistance of the material to the tool.	\(lbf\)	\(N\)
\(CS\)  =  Cutting Speed	The relative velocity between the cutting tool and the workpiece surface. (\(SS\) = Surface Speed)	\(in\;/\;min\)	\(mm\;/\;min\)
\(CD\)  = Cutting OD at Cutting Depth		\(in\)	\(mm\)
\(CT\)  =  Cutting Time	The time when the machine is actually processing material.	\(min\)	\(min\)
\(CD\)  =  Cutter Diameter	The diameter of the circle that the cutting edges of a tool form as it rotates.	\(in\)	\(mm\)
\(DOC\)  =  Depth of Cut		\(in\)	\(mm\)
\(LOC\)  =  Length of Cut		\(in\)	\(mm\)
\(WOC\)  =  Width of Cut		\(in\)	\(mm\)
\(FPT \)  =  Feed per Tooth	The amount of the material removed by each cutting edge of the tool as it moves through the work material.  (The same as \(IPT\) = Inches per Tooth)	\(in\;/\;tooth\)	\(mm\;/\;tooth\)
\(FPR \)  -  Feed per Revolution	The distance a cutting tool travels in a single spindle revolution.  (The same as \(IPR\) = Inches per Revolution)	\(ft\;/\;rev\)	\(m\;/\;rev\)
\(IPM\)  =  Inches per Minute	The rate at which a cutting tool advances into the workpiece during a machining operation.	\(in\;/\;min\)	-
\(IPR\) = Inches per Revolution	The distance in inches that a cutting tool travels for each revolution of the spindle during a machining operation.	\(in\;/\;rev\)	\(mm\;/\;rev\)
\(IPT\) = Inches per Tooth	The amount of material removed by each cutting edge of a tool during one revolution of the tool.	\(in\;/\;tooth\)	\(mm\;/\;tooth\)
\(n\)  =  Machine Efficiency	The percentage of time the machine spends machining compared to the total time available for machining.	-	-
\(MRR \)  = Metal Removal Rate	It measures how much material is removed from a part in a given period of time.	\(in^3\;/\;min\)	\(mm^3\;/\;min\)
\( HP_m \) = Motor Horsepower	The amount of power a motor can deliver to drive a machine tool.	\(lbf-ft/sec\)	\(J\;/\;s\)
\(Z\)  =  Number of Teeth		-	-
\( RPM \) = Revolutions per Minute	The number of complete rotations that a machining tool makes in one minute while performing a cutting operation.	\(rev\;/\;min\)	\(rev\;/\;min\)
\(SS\)  =  Spindle Speed	The rotational speed of the spindle that holds the cutting tool in a machine tool.	\(rev\;/\;min\)	\(rev\;/\;min\)
\( \tau_s \) (Greek symbol tau) = Spindle Torque	The rotational force that the machine’s spindle can apply to the cutting tool during operations.	\(lbf-in\)	\(N-mm\)
\(SFM\) = Surface Feet per Minute	The speed at which a cutting tool or workpiece moves past the cutting edge of a tool.	\(ft\;/\;min\)	\(m\;/\;min\)
\( TF \) = Table Feed	The linear speed at which the workpiece or cutting tool moves during a machining operation	\(in\;/\;min\)	\(mm\;/\;min\)