Explanation: A metal lathe rotates the workpiece while a stationary cutting tool is fed into it, removing material to produce cylindrical, conical, and faced surfaces. The workpiece rotates; the tool moves linearly.
What is the primary function of a milling machine?
Explanation: In milling, the cutting tool rotates while the workpiece is clamped to a table that moves in X, Y, and Z axes. This allows the creation of flat surfaces, slots, pockets, and complex 3D geometries.
What unit is commonly used to express cutting speed for metal machining operations?
Explanation: Cutting speed (SFM or m/min) describes the linear speed at which the cutting edge moves relative to the workpiece surface. RPM is calculated from the cutting speed and workpiece/cutter diameter. Recommended SFM values are material-specific.
What is the formula to calculate RPM for a metal lathe operation?
Explanation: The formula converts surface feet per minute to revolutions per minute based on the workpiece diameter. The constant 3.82 is derived from 12/Ο. For example, machining mild steel (100 SFM) at 1" diameter: RPM = (100 Γ 3.82) / 1 = 382 RPM.
What is "feed rate" in machining?
Explanation: Feed rate determines how much material the tool removes per revolution. On a lathe, it is expressed in inches per revolution (IPR). On a mill, it is expressed in inches per tooth (IPT) multiplied by the number of teeth and RPM to get inches per minute (IPM).
What is the purpose of cutting fluid (coolant) in metal machining?
Explanation: Cutting fluid serves multiple functions: it removes heat from the cutting zone (preventing tool softening and workpiece distortion), lubricates the interface between the chip and tool face (reducing friction), and flushes chips away from the cut. Proper coolant use can increase tool life by 3-5x.
What material are most general-purpose lathe cutting tool inserts made from?
Explanation: Cemented carbide inserts (ISO grades like P, M, K designations) are the standard for modern machining. They maintain hardness at high temperatures (up to 1800Β°F), allow faster cutting speeds than HSS, and are available in indexable insert form for quick changes. HSS is still used for some operations and in smaller shops.
What does "depth of cut" refer to in metal machining?
Explanation: Depth of cut (DOC) is the amount of material removed per pass, measured radially from the original surface to the cut surface. On a lathe, a 0.050" depth of cut removes 0.050" from the radius, reducing the diameter by 0.100". Roughing passes use larger DOC; finishing passes use smaller DOC.
What are the three primary axes of movement on a milling machine?
Explanation: The X-axis moves the table left and right, the Y-axis moves the saddle (and table) toward or away from the column, and the Z-axis moves the spindle head or quill up and down. These three axes allow the cutter to reach any point on the workpiece.
What safety device automatically disengages the lathe carriage feed at a preset position?
Explanation: The carriage stop is an adjustable mechanical device that automatically disengages the power feed when the carriage reaches a preset position. This prevents the tool from crashing into the chuck or tailstock and enables repeatable cut lengths.
What is the difference between climb milling and conventional milling?
Explanation: In conventional (up) milling, the cutter teeth engage the thinnest part of the chip first. In climb (down) milling, teeth engage the thickest part first. Climb milling produces a better surface finish and generates less heat but requires a machine with minimal backlash to prevent the cutter from pulling the workpiece.
What is the purpose of a lathe's compound rest?
Explanation: The compound rest sits on top of the cross slide and can be rotated to any angle. This allows the cutting tool to be fed at an angle to the workpiece axisβessential for cutting tapers, chamfers, and threading (where the compound is typically set to 29Β° or 29.5Β° for 60Β° thread forms).