Lathe Machine

Introduction

If you are new to metalworking lathes and lathe work, this page will help you understand some of the basic concepts, terminology and capabilities. In essence, a lathe, whether for woodworking or metalworking, rotates a cylindrical work piece along its axis and removes material from the work piece to form it into a specific shape.

On a woodworking lathe, the cutting tools are usually hand-held against a support and are moved in and out and back and forth along the surface of the work by hand to form a shape such as a table leg.

On metalworking lathes, the cutting tools are held rigidly in a tool holder that is mounted on a movable platform called the carriage. The tool is moved in and out by means of hand cranks and back and forth either by hand cranking or under power from the lathe. The result is that material can be removed from the work piece under very precise control to produce shapes that are truly precision made. Dimensional accuracies of one-one-thousandth of an inch (.001") are typical. However, because of the inherent rotational nature of a lathe, the vast majority of the work produced on it is basically cylindrical in form. In spite of this, the lathe is an extremely versatile machine capable of producing a surprising variety of objects.

 

 

 

 

 

History

The lathe is an ancient tool, dating at least to the Egyptians and known and used in Assyria, Greece, the Roman and Byzantine Empires.

The origin of turning dates to around 1300 BC when the Egyptians first developed a two-person lathe. One person would turn the wood work piece with a rope while the other used a sharp tool to cut shapes in the wood. The Romans improved the Egyptian design with the addition of a turning bow. Early bow lathes were also developed and used in Germany, France and Britain. In the Middle Ages a pedal replaced hand-operated turning, freeing both the craftsman's hands to hold the woodturning tools. The pedal was usually connected to a pole, often a straight-grained sapling. The system today is called the "spring pole" lathe (see Pole lathe). Spring pole lathes were in common use into the early 20th century. A two-person lathe, called a "great lathe", allowed a piece to turn continuously (like today's power lathes). A master would cut the wood while an apprentice turned the crank.^[1]

During the Industrial Revolution, mechanized power generated by water wheels or steam engines was transmitted to the lathe via line shafting, allowing faster and easier work. The design of lathes diverged between woodworking and metalworking to a greater extent than in previous centuries. Metalworking lathes evolved into heavier machines with thicker, more rigid parts. The application of lead screws, slide rests, and gearing produced commercially practical screw-cutting lathes. Between the late 19th and mid-20th centuries, individual electric motors at each lathe replaced line shafting as the power source. Beginning in the 1950s, servomechanisms were applied to the control of lathes and other machine tools via numerical control (NC), which often was coupled with computers to yield computerized numerical control (CNC). Today manually controlled and CNC lathes coexist in the manufacturing industries.

What is Lathe?

A lathe  is a 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 of rotation.

Lathes are used in woodturning, metalworking, metal spinning, and glass working. Lathes can be used to shape pottery, the best-known design being the potter's wheel. Most suitably equipped metalworking lathes can also be used to produce most solids of revolution, plane surfaces and screw threads or helices. Ornamental lathes can produce three-dimensional solids of incredible complexity. The material can be held in place by either one or two centers, at least one of which can be moved horizontally to accommodate varying material lengths. Other work holding methods include clamping the work about the axis of rotation using a chuck or cullet, or to a faceplate, using clamps or dogs.

Examples of objects that can be produced on a lathe include candlestick holders, cue sticks, table legs, bowls, baseball bats, musical instruments (especially woodwind instruments), crankshafts and camshafts.

Glossary of Lathe Terms

Apron	Front part of the carriage assembly on which the carriage hand wheel is mounted
Bed	Main supporting casting running the length of the lathe
Carriage	Assembly that moves the tool post and cutting tool along the ways
Carriage Hand wheel	A wheel with a handle used to move the carriage by hand by means of a rack and pinion drive
Chuck	A clamping device for holding work in the lathe or for holding drills in the tailstock. Drill chucks are sometimes referred to as Jacobs Chucks, a brand name that popularized that style of chuck.
Compound	Movable platform on which the tool post is mounted; can be set at an angle to the work piece. Also known as the compound slide and compound rest.
Compound Hand wheel	A wheel with a handle used to move the compound slide in and out. Also known as the compound feed.
Cross Feed	A hand wheel or crank that moves the cross-slide by turning a screw. Also the action of moving the cross slid using the cross feed hand wheel.
Cross-slide	Platform that moves perpendicular to the lathe axis under control of the cross-slide hand wheel
Half nut Lever	Lever to engage the carriage with the lead screw to move the carriage under power
Headstock	The main casting mounted on the left end of the bed, in which the spindle is mounted. Houses the spindle speed change gears.
Lead screw	Precision screw that runs the length of the bed. Used to drive the carriage under power for turning and thread cutting operations. Smaller lead screws are used within the cross-slide and compound to move those parts by precise amounts.
Spindle	Main rotating shaft on which the chuck or other work holding device is mounted. It is mounted in precision bearings and passes through the headstock.
Tailstock	Cast iron assembly that can slide along the ways and be locked in place. Used to hold long work in place or to mount a drill chuck for drilling into the end of the work.
Tailstock Hand wheel	A wheel with a handle used to move the tailstock ram in and out of the tailstock casting.
Tool post	A holding device mounted on the compound  into which the cutting tool is clamped
Ways	Precision ground surfaces along the top of the bed on which the saddle rides. The ways are precisely aligned with the centerline of the lathe.

 

 

 

  

 

 

 

 

 

Types of Lathe Machines

Wood Lathes

The simplest lathe type is the wood lathe. As the name suggests, it is designed for turning wood. Wood lathes are small machines consisting of a bed, headstock, tailstock and tool rest. There are no precision ways as are found on a metal-working machine, since the cutting tools are moved by hand and not by machine power. Great skill is needed to control the cutting tool to accurately turn smooth curves and complex contours on the work piece.

The spindle is usually driven by a belt connected to a motor, and speed changes are made by manually moving the belt to one of several pulleys mounted to the back of the spindle.

Lathe tools are held manually against the work, with the support of the tool rest. The tool rest is adjustable and is clamped to the bed at a position convenient for the operation at hand.  

Engine Lathes

Engine lathes are the classic metal turning workhorses of the production machine shop. They come in many sizes and are adaptable to working virtually any material. These machines have a longitudinal bed to which is mounted a headstock and tailstock.

As in the wood lathe, the headstock contains the spindle. However, the spindle drive is more complex, including variable speed capability or selectable gearing to provide a much wider range of speeds.

A carriage moves back forth on bed ways for longitudinal turning. A cross-slide and compound rest are mounted to the top of the carriage to provide cross and angular cutting capability.

The lathe cutting tools are moved against the work manually using hand wheels or automatically under the power of a lead screw that is driven by gears in the headstock.

         

 Tool room Lathe

The tool room lathe is a small- to medium-sized engine lathe specially designed for high-precision work. These machines find use in tool and die shops, where custom parts and precision fixtures are produced, often in support of production machining operations.

Tool room lathes are manufactured with special attention to spindle accuracy, smooth operation and precise alignment of the carriage and cross slide. A tool room lathe is capable of better accuracy and precision than a standard engine lathe.

Turret Lathe

Turret lathes are used in production machine shops where several sequential operations are needed on single work piece. It is costly and time consuming to remove a work piece from one machine and hold it in another. Removing and beholding a work piece also introduces errors in work alignment and machining accuracy.

The turret lathe has a rotating turret mounted to the carriage so that as soon as an operation with one tool is completed, the turret is indexed to bring another tool into working position. The part is then machined again without having to remove it from the chuck or collect. Eight (or more) different operations can be performed on a work piece using this type of machine.

CNC Lathe

Computer numerically controlled lathes have largely supplanted engine lathes in production machining environments. CNC lathes offer the advantages of greater powered axis drives, feedback control to monitor and maintain tool positioning and high-speed repeatability of complex machine motions. Once a program is verified, an operation can be quickly set up again without the need for tedious manual adjustments.

CNC lathes excel at cutting curved contours without the need for specially shaped tools. This is done by programmed variation of the speed of two motion axes and the spindle simultaneously---an operation that is impossible with an engine lathe.

Lathe Specifications

FEATURE	4000(4100)	4400(4410)
Swing over bed	3.50" (90 mm)	3.50" (90 mm)
Swing over carriage	1.75" (45 mm)	1.75" (45 mm)
Distance between centers	8.00" (200 mm)	17.00" (430 mm)
Hole through spindle	.405" (10 mm)	.405" (10 mm)
Spindle nose thread	3/4"-16 T.P.I.	3/4"-16 T.P.I .
Spindle nose taper	#1 Morse	#1 Morse
Travel of crosstie	4.25" (110 mm)	4.25" (110 mm)
Taper of tailstock spindle	#0 Morse	#0 Morse.
Protractor graduations	0° to 45° by 5°	0° to 45° by 5°
Hand wheel graduations	.001" (.01 mm)	.001" (.01 mm)
Length overall	24" (610 mm)	32.25" (820 mm)
Width overall	7.5" (190 mm)	8.75" (220 mm)
Height overall	6" (150 mm)	8" (200 mm)
Shipping weight	24 lb. (10.9 kg)	30 lb. (13.6 kg)
Motor/Speed Control	90 Volts DC with electronic speed control that accepts any incoming current from 100VAC to 240 VAC, 50 Hz or 60 Hz. Click here for more detailed motor and other machine specifications.
Spindle speed range	70-2800 RPM continuously variable by electronic speed control

Lathe Safety

1.      YOU are responsible for your own safety and proper machine operation.

2.      As small as it is, the mini lathe, like any power tool, can be dangerous if used improperly. If you are new to metal working, get in the habit right from the start of rigorously following good safety practices. Here are some tips:

3.      Always wear eye protection - preferably industrial quality safety glasses with side-shields. The lathe can throw off sharp, hot metal chips at considerable speed as well as spin off spirals of metal that can be quite hazardous. Don't take chances with your eyes.

4.      Wear short sleeve shirts, if possible, or shirts with snugly fitting cuffs if long sleeve. Loose sleeves can catch on rotating work and quickly pull your hand or arm into harm's way.

5.      Wear shoes - preferably leather work shoes - to protect your feet from sharp metal chips on the shop floor and from tools and chunks of metal that may get dropped.

6.      Remove wrist watches, necklaces, chains and other jewelry. It's a good idea even to remove your wedding ring since it can catch on rotating work and severely damage your ring finger and hand. 

7.      Tie back long hair so it can't get caught in the rotating work. Think about what happens to your face if your hair gets entangled.

8.      Always double check to make sure your work is securely clamped in the chuck or between centers before starting the lathe. Start the lathe at low speed and increase the speed gradually.

9.      Get in the habit of removing the chuck key immediately after use. Some users recommend never removing your hand from the chuck key when it is in the chuck. The chuck key can be a lethal projectile if the lathe is started with the chuck key in the chuck.

10.  Keep your fingers clear of the rotating work and cutting tools. This sounds obvious, but I am often tempted to break away metal spirals as they form at the cutting tool.

11.  Avoid reaching over the spinning chuck. For filing operations, hold the tang end of the file in your left hand so that your hand and arm are not above the spinning chuck.

Never use a file with a bare tang - the tang could be forced back into your wrist or palm.

Application

Ø  A CNC lathe is a machine tool designed to remove material from a rotating work piece, using a cutting tool. Some lathes can form hollow parts by a process called metal spinning. These parts have circular cross-sections. Metal and other materials can be turned on a lathe, including wood and plastics. CNC controlled lathes use a computer to control the process of making each part with repeated

Ø  A metal lathe usually spins the work piece along a horizontal axis. A mandrel or chuck is mounted to the Headstock of the lathe. A follower block or tail block is mounted to the tailstock. A blank piece is clamped to the

Ø  Lathe and pressure is applied to the blank via a cutting tool. Material is cut away on each pass across the blank.

Ø  After each pass, the lever arm is moved closer to the final position. Eventually, when the proper amount of material has been removed, the part is completed.

Ø  Yukawa AC drives can be interlocked with the CNC control systems so the operation of the CNC controller and the AC drive are synchronized.

Ø  In addition, the Energy Saving Mode in Yukawa AC drives automatically detect changes to the amount of torque required during shaping and finishing phases. This feedback enables the drive to quickly detect changes as the cutting tool becomes dull.