The Metalworking Lathe
Unit 58
Metalwork Technology and
Practice
Lathe Operation Principle
• Lathes operate on the principle of a cutting
tool removing metal as it is being fed into a
revolving work piece. (Fig 58-2 pg. 451)
Kinds of Lathes
• Manually Operated Lathe: Used to make single parts
and small quantities of multiple parts or for repair of worn
parts.
• Screw Machines and Turret Lathes: Used for production
runs of a few hundred parts.
• Numerically Controlled and CNC: Used for short but
rapid production runs. These are replacing the Manual
Lathes.
• Automatic Lathes: Used for production runs of
thousands identical parts
• Vertical Turret Lathes: Used to machine parts of a large
diameter.
Sizing Lathes
• Lathes come in various sizes
• Lathes are sized by the swing and bed length.
• Swing: Is the largest diameter work piece that
can be turned on the machine.
– The swing is measured by the distance from the
center point of the chuck to the bottom of the bed.
Multiply this measurement times two to reach the
largest diameter stock that can be turned.
– The bed is measured from front to the back of the
machine.
– (See Fig. 58-9 pg 453)
Lathe Examples
• 7” x 12” Lathe
• 13” x 40” Lathe
Lathe Main Parts
• Bed: The main frame upon which the machine
is built.
• Headstock: Always on the left hand side of the
bed. This contains the drive mechanisms of the
lathe (motor). This part will accept different
chucks.
• Tailstock: Always clamped to the right side on
the lathe bed. This part moves on the bed. This
part will accept live centers, dead centers, drill
chucks, tapered shank drills, and reamers.
• Both headstock and tailstock contain spindles.
7
5
4
9
6
10
8
11
3
12
2
13
15
1
14
Headstock Drive System
• Belt Driven: This is the most common upon
older lathes. A V-belt will drive all the moving
parts off the electric motor.
• Gear Driven: A series of gears operate the
moving parts
• V-belt and Manual-shift systems require the
operator to change speeds by changing the
belts to different pulleys.
• Lever-shift systems and variable speed drive
systems allow the operator to change speeds by
the movement of a lever.
Main Power Switch
Headstock
Tool Post
Chuck
Compound
Rest Knob
Bed ways
Tailstock
Tailstock Handle
Speed Change Levers
Power Feed
Clutch
Feed Change Levers
Friction Clutch
Carriage Hand Wheel
Emergency Foot Stop
Cross Slide
Carriage Feed
• Longitudinal Feed: When the tool is fed
along the work, parallel with the bed.
– Turning
– Boring
• Cross Feed: When the tool is fed across
the end of the work piece.
– Facing
• (See Fig. 58-17 pg. 456)
Carriage Control
• (See Fig. 58-20 pg. 457)
• Apron Handwheel: Used for manual
longitudinal movement.
• Cross-feed Knob: Used to move the
cross slide in and out manually.
• Compound Rest: Holds the toolholder and
cutting tool that is mounted on the crossslide which is fed manually with the
compound-rest knob.
Main Power Switch
Headstock
Tool Post
Chuck
Compound
Rest Knob
Bed ways
Tailstock
Tailstock Handle
Speed Change Levers
Power Feed
Clutch
Feed Change Levers
Friction Clutch
Carriage Hand Wheel
Emergency Foot Stop
Cross Slide
Lathe Safety
Safety Precautions
• Always wear safety glasses
• Do not wear loose clothing or long sleeves
– Short sleeves are recommended
• Never wear a ring or watch
– Rings and watches can get caught in
revolving work or lathe parts
– If metal objects would fall on the hand this
would cause the ring to bend or break.
Removing a bent ring is painful!!!
Safety Precautions
• Know your lathe parts
– Not knowing what certain levers do and how
they operate could can be dangerous
– Know where your emergency shut down
switches are located at
• Do not operate a lathe without the designed
safety features
• Stop the lathe then shut off the power when
checking measurements and removing stock
from chuck or spindle
Safety Precautions
• Do not attempt to measure revolving parts
• If the machine is equipped, use the emergency
foot stop to stop the lathe. Never try to stop the
lathe by hand!!!
• Never use a rag or paper towel to clean the
parts while they are revolving in the lathe
• Make sure that all parts are secured tightly in the
lathe before starting. Parts could fly out if they
are not.
Safety Precautions
• The chuck key is always part of your hand while
installing parts into the chuck. Never remove your hand
from the chuck key until all parts are secured properly
and the chuck key has been placed in its designated
location.
• If the lathe is started with the chuck key in place the
following could happen
– The chuck key could fly out and injure someone or hit the lights
– The chuck key could become jammed against the lathe bed,
damaging the wrench, lathe bed, chuck, and lathe spindle
Safety Precautions
• Keep the floor free from grease, oil, metal cutting
tools, and work pieces
• No horseplay
• Remove the metal chips / shavings from the
lathe with a chip brush. Never use a cloth or
your hands.
• Move the carriage out of the way or down the
bed while polishing, filing, cleaning, and when
making adjustments to the work.
Methods of Holding
Workpieces in a Lathe
Unit 59
Metalwork Technology and
Practice
Spindle Noses
• Headstock Spindle: Where all work piece
holding devices are attached to and driven by.
• Three types of spindle noses:
– Threaded Spindle Nose: Accommodates chucks and
face plates.
– Cam-Lock Spindle Nose: Notched rods attached to
the back of the chuck are aligned with holes on the
spindle face.
– Long Taper Key-Drive Spindles: The chuck is placed
so that the key on the spindle nose lines up with the
keyway in the chuck.
– See Fig. 59-1, 59-2, and 59-3)
Lathe Chucks
• Five Kinds of Lathe Chucks:
–
–
–
–
–
Four Jaw
Three Jaw
Collet
Spindle
Step
• (See Fig 59-4, 59-5, 59-6, 59-7, 59-8, and 59-9
on pgs. 461, 462, and 463)
• To install and remove a chuck follow the
instructions laid out in section 59-3 on pgs 462
and 463
LATHE CUTTING TOOLS,
TOOLHOLDERS, CUTING
SPEEDS, AND FEED
SELECTION
UNIT 60
Metalwork
Technology and Practice
Tool Bits
• Defined: Cutting tools
for lathes
• Types of Tool Bits
– Left Hand Turning
Tool
– Left Hand Facing Tool
– Right Hand Turning
Tool
– Right Hand Facing
Tool
– Round Nose
– Round Nose Turning
Tool
– Threading Tool
– Boring Tool
– Cut-Off Tool
– Inside Turning Tool
Lathe Tool Composition
•
•
•
•
•
•
High Speed Steel
Cast Alloys
Cemented Carbide
Ceramics
Cubic Boron Nitride
Diamond
Lathe Cutting Tool Bits
Cutting Tool Terms
• Cutting Edge: The part that does the cutting
– Side Cutting Edge
– End Cutting Edge
•
•
•
•
Face: Top Tool Surface
Flank: Side of the tool below the side cutting edge
Nose: Point of the tool
Nose Angle: Angle formed by the side cutting edge and
the end cutting edge
• Nose Radius: The dimension of the arc that forms a
round nose
• Shank: Body of the tool
Cutting Tool Terms (cont.)
• Side Cutting Edge: The angle formed by
the side cutting edge
• End Cutting Edge: The angle formed by
the end cutting edge
• Side Relief: The angle between the tool
flank and the original side of the tool
• End Relief: The angle between the end of
the tool and a line drawn 90 degrees to the
base of the toolholder
Cutting Tool Terms (cont.)
• Left hand cutting tool: Has cutting edge
on the right
• Right hand cutting tool: Has cutting edge
on the left
ToolHolders
• The NCWHS lab uses a multiple tool post,
tool holder system.
• The tool bit is inserted into a block where
four tool bits can be utilized
Lathe Tool Post Systems