MACH 118: Lathe & Vertical Mill I Cutting Speeds

Determine correct feeds for various machining operations. OBJECTIVES tab After completing this unit, you should be able to… Calculate correct cutting speeds for various machine tools and grinding machines. Determine correct feeds for various machining operations.

Cutting Speeds SPEEDS AND FEEDS FOR MACHINE TOOLS tab Cutting speeds (CS) are given in tables for cutting tools, based on surface feet per minute (fpm/sfpm). Surface feet per minute means the tool moves past the work or the work moves past the tool at a rate based on the number of feet that pass the tool in one minute.

SPEEDS AND FEEDS FOR MACHINE TOOLS tab Cutting Speeds Because machine spindle speeds are given in revolutions per minute (rpm), they can be derived in the following manner:

SPEEDS AND FEEDS FOR MACHINE TOOLS tab Cutting Speeds This simplified formula is most common in machine shop practice & applies to the full range of machine tool operations. Including lathe, milling machine & the drill press. The simplified formula is used in your text book.

Cutting Speeds SPEEDS AND FEEDS FOR MACHINE TOOLS tab Cutting & starting values for common materials. Watch cutting action & make speed corrections as needed. Cutting speeds depend upon variables and should be considered approximations. WORK MATERIAL HIGH-SPEED STEEL CARBIDE Aluminum Brass Bronze Cast Iron Mild Steel Tool Steel Stainless Steel 400 300 100 50 80 60 40 x 3.5

Cutting Speeds SPEEDS AND FEEDS FOR MACHINE TOOLS tab Cutting speed for carbide tools is normally 3-4 times that of high-speed cutting tools. Carbide cutting tools will chip or break up quickly at too-low cutting speeds. Blue colored steel chips indicate higher temperature caused by high cutting speed and/or dull tools. Blue chips are acceptable & desirable when using carbides, but not when using high-speed steel tools. Chips should not be discolored at all with high-speed tools, especially when cutting fluids are used.

SPEEDS AND FEEDS FOR MACHINE TOOLS tab Cutting Speeds Lower cutting speeds are used to machine hard or tough materials, or where heavy cuts are taken. Higher cutting speeds are used in machining softer materials to achieve better surface finishes. Cutting speeds for drills are the same for drilling operations both where the drill rotates and where the work rotates and the drill remains stationary.

SPEEDS AND FEEDS FOR MACHINE TOOLS tab Feeds Feeds on milling machines refer to the rate at which the workpiece material is advanced into the cutter by table movement. Or where the cutter is advanced into the workpiece in the manner of a drill cutting on its end. Because each tooth on a multitooth milling cutter makes a chip, chip thickness depends on amount of table feed (cpt).

SPEEDS AND FEEDS FOR MACHINE TOOLS tab Feeds Feed rate in milling is measured in inches per minute (ipm) and is calculated by the formula: ipm = CPT x N x rpm ipm = feed rate, in inches per minute CPT = Chip Per Tooth N = Number of teeth in the cutter being used rpm = revolutions per minute of the cutter

Feeds SPEEDS AND FEEDS FOR MACHINE TOOLS tab Feeds for end mills used in vertical milling machines range from .001 to .002 in. feed per tooth for small- diameter cutters in steel work material to .010 in. feed per tooth for large cutters in aluminum workpieces.

REVIEW Calculate the rpm’s for the following: 640 rpm ½” HSS cutter machining mild/machine steel. 640 rpm

REVIEW Calculate the rpm’s for the following: 107 rpm n2.25” HSS cutter machining tool steel. 107 rpm

REVIEW Calculate the rpm’s for the following: 116 rpm n35 mm cutter machining stainless steel. 116 rpm

REVIEW Calculate the rpm’s for the following: 1422 rpm n20mm carbide cutter machining 1018 steel. 1422 rpm

REVIEW Calculate the rpm’s for the following: 379 rpm n75mm carbide cutter machining 1018 steel. 379 rpm

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