History • Lathe forerunner of all machine tools • First application was potter's wheel – Rotated clay and enabled it to be formed into cylindrical shape • Very versatile (many attachments) – Used for turning, tapering, form turning, screw cutting, facing, drilling, boring, spinning, grinding and polishing operations • Cutting tool fed either parallel or right angles
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History• Lathe forerunner of all machine tools
• First application was potter's wheel– Rotated clay and enabled it to be formed into
cylindrical shape
• Very versatile (many attachments)– Used for turning, tapering, form turning, screw
cutting, facing, drilling, boring, spinning, grinding and polishing operations
• Cutting tool fed either parallel or right angles
Special Types of Lathes
• Engine lathe– Not production lathe, found in school shops,
toolrooms, and jobbing shops– Basic to all lathes
• Turret lathe– Used when many duplicate parts required– Equipped with multisided toolpost (turret) to
which several different cutting tools mounted• Employed in given sequence
Engine Lathe
• Accurate and versatile machine• Operations
– Turning, tapering, form turning, threading, facing, drilling, boring, grinding, and polishing
• Three common– Toolroom– Heavy-duty– Gap-bed
Lathe Size and Capacity
• Designated by largest work diameter that can be swung over lathe ways and generally the maximum distance between centers
• Manufactured in wide range of sizes– Most common: 9- to 30- in. swing with
capacity of 16 in. to 12 feet between centers– Typical lathe: 13 in. swing, 6 ft long bed, 36 in.– Average metric lathe: 230-330 mm swing and
Special adapter fitted into taper of headstock spindle, and hollow draw bar having internal thread inserted in opposite end of headstock spindle. It draws collet into tapered adapter causing collet to tighten on workpiece.
• Be aware of safety requirements in any area of shop
• Always attempt to observe safety rules
• Failure results in:– Serious injury– Resultant loss of time and pay– Loss of production to company
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Safety Precautions
• Lathe hazardous if not operated properly
• Important to keep machine and surrounding area clean and tidy
• Accidents usually caused by carelessness
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Safety Precautions
• Always wear approved safety glasses
• Rollup sleeves, remove tie and tuck in loose clothing
• Never wear ring or watch
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Safety Precautions
• Do not operate lathe until understand controls• Never operate machine if safety guards
removed• Stop lathe before measure work or clean, oil
or adjust machine• Do not use rag to clean work or machine
when in operation– Rag can get caught and drag in hand
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Safety Precautions
• Never attempt to stop a lathe chuck or driveplate by hand
• Be sure chuck or faceplate mounted securely before starting– If loose, becomes dangerous missile
• Always remove chuck wrench after use– Fly out and injure someone– Become jammed, damaging wrench or lathe
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Safety Precautions
• Move carriage to farthest position of cut and revolve lathe spindle one turn by hand– Ensure all parts clear without jamming– Prevent accident and damage to lathe
• Keep floor around machine free from grease, oil, metal cuttings, tools and workpieces– Oil and grease can cause falls– Objects on floor become tripping hazards
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Safety Precautions
• Avoid horseplay at all times
• Always remove chips with brush– Chips can cause cuts if use hands– Chips become embedded if use cloths
• Always remove sharp toolbit from toolholder when polishing, filing, cleaning, or making adjustments
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Objectives
• Mount and/or remove lathe centers properly
• Align lathe centers by visual, trial-cut, and dial-indicator methods
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Lathe Centers
• Work machined between centers turned for some portion of length, then reversed, and other end finished
• Critical when machining work between centers that live center be absolutely true– Concentric work
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To Mount Lathe Centers
• Remove any burrs from lathe spindle, centers, or spindle sleeves
• Clean tapers on lathe centers and in headstock and tailstock spindles
• Partially insert cleaned center in lathe spindle• Force center into spindle• Follow same procedure when mounting
tailstock center• Check trueness of center
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To Remove Lathe Centers
• Live center– Use knockout bar pushed through headstock
spindle (slight tap)– Use cloth over center and hold to prevent damage
• Dead center– Turn tailstock handwheel to draw spindle back
into tailstock• End of screw contacts end of dead center, forcing it
out of spindle
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Grinding Lathe Cutting Tool
• Wide variety of cutting tools for lathe– All have certain angles and clearances regardless
of shape
Shape and Dimensions of General-purpose Lathe Toolbit
• Process if impressing a diamond-shaped or straight-line patter into the surface of the workpiece– Improve its appearance– Provide better gripping surface– Increase workpiece diameter when press fit
required
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Knurling
• Diamond- and straight-pattern rolls available in three styles– Fine