Saturday, August 09, 2008

Introduction to Lathe

Lathe Machine
  • machine tool which spins a block of material to perform various operations such as cutting, sanding , knurling, drilling or deformation with tools that are applied to the work piece to create an object which has symmetry about an axis or rotation.
  • usually lathe is used in wood turning, metal working, metal spinning and glass working.
  • lathe also can be used to shape pottery and lathe is the best known design being the potter's wheel.

Above figure is the parts that are in a lathe machine.

  • Bed is mainly support the whole machine
  • Carriage is assembly that moves the tool post and cutting tool along the ways
  • Carriage Hand wheel is a wheel with a handle used to move the carriage by hand by means of a rack and ponion drive
  • A chuck is a clamping device for holding work in the lathe
  • Apron is the front part of the carriage assembly on which carriage hand wheel is mounted
  • Cross slide is a platform that moves perpendicular to the lathe axis under control of the cross slide hand wheel
  • Cross slide hand wheel is a wheel with handle used to move the cross slide in and out.
  • Halfnut lever is the lever to engage the carriage with leadscrew to move the carriage under power
  • lead screw is a precision screw that runs the length of the bed. it is used to drive the carriage under power for turning and thread cutting operations.
  • swing is a dimension representing the largest diameter work piece that a lathe can rotate
  • tailstock is a cast iron assembly that can be slide along the ways and be locked in place. used to hold long work in place or mount a drill chuck for drilling into end of the work
  • Ram is a piston type shaft that can be moved in and out of the tailstock by turning the tailstock hand wheel.
  • Tool is a cutting tool used to remove metal from the work piece and usually made of high speed steel or carbide.
  • ways is a precision ground surfaces along top of the bed on which saddle rides. the ways are precisely aligned with the centerline of the lathe

Fig 1. This picture above shows the current lathe machine that we are using in this days

Fig 2. Lathe Machine with the work piece ready for cutting

Fig 3.

Woodworking lathes

  • oldest variety.
  • All other varieties are descended from these simple lathes.
  • An adjustable horizontal metal rail - the tool rest - between the material and the operator accommodates the positioning of shaping tools, which are usually hand-held. With wood, it is common practice to press and slide sandpaper against the still-spinning object after shaping to smooth the surface made with the metal shaping tools.

There are also woodworking lathes for making bowls and plates, which have no horizontal metal rail, as the bowl or plate needs only to be held by one side from a metal face plate. Without this rail, there is very little restriction to the width of the piece being turned. Further detail can be found on the wood turning page.

Metalworking lathes

  • metal is removed from the workpiece using a hardened cutting tool, which is usually fixed to a solid moveable mounting called the "toolpost", which is then moved against the workpiece using handwheels and/or computer controlled motors.
  • The toolpost is operated by leadscrews that can accurately position the tool in a variety of planes. The toolpost may be driven manually or automatically to produce the roughing and finishing cuts required to turn the workpiece to the desired shape and dimensions, or for cutting threads, gear, etc.
  • Cutting Fluid may also be pumped to the cutting site to provide cooling, lubrication and clearing of swarf from the workpiece. Some lathes may be operated under control of a computer for mass production of parts.

Metalworking lathes are commonly provided with a variable ratio gear train to drive the main leadscrew. This enables different pitches of threads to be cut. Some older gear trains are changed manually by using interchangeable gears with various numbers of teeth, while more modern or elaborate lathes have a quick change box to provide commonly used ratios by the operation of a lever.

The workpiece may be supported between a pair of points called centres, or it may be bolted to a faceplate or held in a chuck. A chuck has movable jaws that can grip the workpiece securely.

Cue lathes

  • Cue lathes function similar to turning and spinning lathes allowing for a perfectly radially-symmetrical.
  • They can also be used to refinish cues that have been worn over the years.

Glass working lathes

  • similar in design to other lathes, but differ markedly in how the workpiece is modified.
  • slowly rotate a hollow glass vessel over a fixed or variable temperature flame.
  • The source of the flame may be either hand-held, or mounted to a banjo/cross slide that can be moved along the lathe bed.
  • The flame serves to soften the glass being worked, so that the glass in a specific area of the workpiece becomes malleable, and subject to forming either by inflation or by deformation with a heat resistant tool. Such lathes usually have two headstocks with chucks holding the work, arranged so that they both rotate together in unison.
  • Air can be introduced through the headstock chuck spindle for glassblowing. The tools to deform the glass and tubes to blow (inflate) the glass are usually handheld.

Metal spinning lathes

  • a disk of sheet metal is held perpendicularly to the main axis of the lathe, and tools with polished tips (spoons) are hand held, but levered by hand against fixed posts, to develop large amounts of torque/pressure that deform the spinning sheet of metal.
  • Metal spinning lathes are almost as simple as wood turning lathes. Typically, metal spinning lathes require a user-supplied rotationally symmetric mandrel, usually made of wood, which serves as a template onto which the workpiece is moulded

Given the advent of high speed, high pressure, industrial die forming, metal spinning is less common now than it once was, but still a valuable technique for producing one-off prototypes or small batches where die forming would be uneconomical.

Reducing Lathe

Many types of lathes can be equipped with accessory components to allow them to reproduce an item: the original item is mounted on one spindle, the blank is mounted on another, and as both turn in synchronized manner, one end of an arm "reads" the original and the other end of the arm "carves" the duplicate.

Reducing lathes are used in coin-making, where a plaster original. Duplicated and reduced on the reducing lathe, generating a master die.

Rotary lathes

A lathe in which softwood logs are turned against a very sharp blade and peeled off in one continuous or semi-continuous roll. Invented by Immanuel Nobel. The first such lathes were set up in the United States in the mid-19th century.

Watchmaker's lathes

  • Delicate but precise metalworking lathes, usually without provision for screw cutting
  • still used by horologists for work such as the turning of balance shafts. A handheld tool called a graver is often used in preference to a slide mounted tool. The original watchmaker's turns was a simple dead centre lathe with a moveable rest and two loose headstocks. The workpiece would be rotated by a bow, typically of horse hair, wrapped around it.

1 comment:

bhavani said...

I am interesting to get information about metal works.I enjoyed a lot while reading your post.Great information.wonderful description!

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