Editing Lathe (section)

== Design ==
The most common design is known as the [[universal lathe]] or parallel lathe. Other general designs include the [[frontal lathe|frontal]] and [[vertical lathe]], and others.

=== Components ===
[[File:Lathe.PNG|thumb|left|A metalworking lathe from 1911, showing component parts:{{ordered list|list_style_type=lower-alpha|
| bed
| carriage (with ''cross''-slide and tool post)
| headstock
| back gear (other gear train nearby drives lead screw)
| cone pulley for a [[Line shaft|belt drive]] from an external power source
| faceplate mounted on spindle
| tailstock
| leadscrew}}
]]

A lathe may or may not have legs, which sit on the floor and elevate the lathe bed to a working height. A lathe may be small and sit on a workbench or table, not requiring a stand.

Almost all lathes have a bed, which is almost always a horizontal beam, although [[CNC]] lathes commonly have an inclined or vertical beam for a bed to ensure that [[swarf]], or chips, falls free of the bed. Woodturning lathes specialized for turning large bowls often have no bed or tail stock, merely a free-standing headstock and a cantilevered tool-rest.

At one end of the bed (almost always the left, as the operator faces the lathe) is a headstock. The headstock contains high-precision spinning bearings. Rotating within the bearings is a horizontal axle, with an axis parallel to the bed, called the [[Spindle (tool)|spindle]]. Spindles are often hollow and have an interior [[Morse taper]] on the spindle nose (i.e., facing to the right / towards the bed) by which work-holding accessories may be mounted to the spindle. Spindles may also have arrangements for work-holding on the left-hand end of the spindle with other tooling arrangements for particular tasks. (i.e., facing away from the main bed) end, or may have a hand-wheel or other accessory mechanism on their outboard end. Spindles are powered and impart motion to the workpiece.

The spindle is driven either by foot power from a treadle and flywheel or by a belt or gear drive from a power source such as electric motor or overhead line shafts. In most modern lathes this power source is an integral electric motor, often either in the headstock, to the left of the headstock, or beneath the headstock, concealed in the stand.

In addition to the spindle and its bearings, the headstock often contains parts to convert the motor speed into various [[Speeds and feeds#Spindle speed|spindle speeds]]. Various types of speed-changing mechanism achieve this, from a cone pulley or step pulley, to a cone pulley with back gear (which is essentially a low range, similar in net effect to the two-speed rear of a truck), to an entire gear train similar to that of a manual-shift automotive [[Transmission (mechanics)|transmission]]. Some motors have electronic rheostat-type speed controls, which obviates cone pulleys or gears.

The counterpoint to the headstock is the [[tailstock]], sometimes referred to as the loose head, as it can be positioned at any convenient point on the bed by sliding it to the required area. The tail-stock contains a barrel, which does not rotate, but can slide in and out parallel to the axis of the bed and directly in line with the headstock spindle. The barrel is hollow and usually contains a taper to facilitate the gripping of various types of tooling. Its most common uses are to hold a hardened steel center, which is used to support long thin shafts while turning, or to hold drill bits for drilling axial holes in the work piece. Many other uses are possible.<ref>{{cite web|url=http://www.inthewoodshop.org/methods/trlathe.shtml|title=Wait a minute...|first=Howard|last=Ruttan|url-status=dead|archive-url=https://web.archive.org/web/20090108083244/http://www.inthewoodshop.org/methods/trlathe.shtml|archive-date=2009-01-08}}</ref>

Metalworking lathes have a carriage (comprising a saddle and apron) topped with a cross-slide, which is a flat piece that sits crosswise on the bed and can be cranked at right angles to the bed. Sitting atop the cross slide is usually another slide called a compound rest, which provides two additional axes of motion, rotary and linear. Atop that sits a toolpost, which holds a [[Tool bit|cutting tool]], which removes material from the workpiece. There may or may not be a [[leadscrew]], which moves the cross-slide along the bed.

Woodturning and metal spinning lathes do not have cross-slides, but rather have [[Banjo (wood lathe)|banjos]], which are flat pieces that sit crosswise on the bed. The position of a banjo can be adjusted by hand; no gearing is involved. Ascending vertically from the banjo is a tool-post, at the top of which is a horizontal tool-rest. In woodturning, hand tools are braced against the tool-rest and levered into the workpiece. In metal spinning, the further pin ascends vertically from the tool-rest and serves as a fulcrum against which tools may be levered into the workpiece.

=== Accessories ===
{{See also|Lathe center}}

[[File:Luenette mit klappbarem oberteil.jpg|thumb|upright|left|A steady rest]]

Unless a workpiece has a taper machined onto it which perfectly matches the internal taper in the spindle, or has threads which perfectly match the external threads on the spindle (two conditions which rarely exist), an accessory must be used to mount a workpiece to the spindle.

A workpiece may be bolted or screwed to a [[lathe faceplate|faceplate]], a large, flat disk that mounts to the spindle. In the alternative, [[Dog (engineering)#Lathe dog|faceplate dogs]] may be used to secure the work to the faceplate.

A workpiece may be mounted on a [[mandrel]], or circular work clamped in a [[Chuck (engineering)#Three jaw|three- or four-jaw chuck]]. For irregular shaped workpieces it is usual to use a four jaw (independent moving jaws) chuck. These holding devices mount directly to the lathe headstock spindle.

In precision work, and in some classes of repetition work, cylindrical workpieces are usually held in a [[collet]] inserted into the spindle and secured either by a draw-bar, or by a collet closing cap on the spindle. Suitable collets may also be used to mount square or hexagonal workpieces. In precision toolmaking work such collets are usually of the draw-in variety, where, as the collet is tightened, the workpiece moves slightly back into the headstock, whereas for most repetition work the dead length variety is preferred, as this ensures that the position of the workpiece does not move as the collet is tightened.

A soft workpiece (e.g., wood) may be pinched between centers by using a [[Lathe center#Drive center|spur drive]] at the headstock, which bites into the wood and imparts torque to it.

[[File:CenterLiveDead.jpg|thumb|right|Running center (top)<br /> Dead center (bottom)]]

A soft dead center is used in the headstock spindle as the work rotates with the centre. Because the centre is soft it can be trued in place before use. The included angle is 60°. Traditionally, a hard [[lathe center#Dead center|dead center]] is used together with suitable lubricant in the tailstock to support the workpiece. In modern practice the dead center is frequently replaced by a [[Lathe center#Running center|running or live center]], as it turns freely with the workpiece—usually on ball bearings—reducing the frictional heat, especially important at high speeds. When clear facing a long length of material it must be supported at both ends. This can be achieved by the use of a [[lathe (metal)#Steady and follower rests|traveling or fixed steady]]. If a steady is not available, the end face being worked on may be supported by a dead (stationary) half center. A half center has a flat surface machined across a broad section of half of its diameter at the pointed end. A small section of the tip of the dead center is retained to ensure concentricity. Lubrication must be applied at this point of contact and tail stock pressure reduced.  A [[lathe carrier]] or [[lathe dog]] may also be employed when turning between two centers.<ref>{{cite web|url=http://www.lathes.co.uk/page13.html|title=Hints & Tips for Using a Lathe|work=“George Wilson’s” Hints and Tips |publisher=Lathes.co.uk|access-date=29 November 2010|archive-url=https://web.archive.org/web/20101201073248/http://www.lathes.co.uk/page13.html|archive-date=1 December 2010|url-status=live|df=dmy-all}}</ref>

In woodturning, one variation of a running center is a [[Lathe center#Cup center|cup center]], which is a cone of metal surrounded by an annular ring of metal that decreases the chances of the workpiece splitting.

A circular metal plate with even spaced holes around the periphery, mounted to the spindle, is called an "index plate". It can be used to rotate the spindle to a precise angle, then lock it in place, facilitating repeated auxiliary operations done to the workpiece.

Other accessories, including items such as taper turning attachments, knurling tools, vertical slides, fixed and traveling steadies, etc., increase the versatility of a lathe and the range of work it may perform.

=== Modes of use ===

When a workpiece is fixed between the headstock and the tail-stock, it is said to be "between centers". When a workpiece is supported at both ends, it is more stable, and more force may be applied to the workpiece, via tools, at a right angle to the axis of rotation, without fear that the workpiece may break loose.

When a workpiece is fixed only to the spindle at the headstock end, the work is said to be "face work". When a workpiece is supported in this manner, less force may be applied to the workpiece, via tools, at a right angle to the axis of rotation, lest the workpiece rip free. Thus, most work must be done axially, towards the headstock, or at right angles, but gently.

When a workpiece is mounted with a certain axis of rotation, worked, then remounted with a new axis of rotation, this is referred to as "eccentric turning" or "multi-axis turning". The result is that various cross sections of the workpiece are rotationally symmetric, but the workpiece as a whole is not rotationally symmetric. This technique is used for camshafts, various types of chair legs.

=== Sizes ===

Lathes are usually 'sized' by the capacity of the work that they may hold. Usually large work is held at both ends either using a chuck or other drive in the headstock and a centre in the tailstock. To maximise size, turning between centres allows the work to be as close to the headstock as possible and is used to determine the longest piece the lathe will turn: when the base of the tailstock is aligned with the end of the bed. The distance between centres gives the maximum length of work the lathe will officially hold. It is possible to get slightly longer items in if the tailstock overhangs the end of the bed but this is an ill-advised practice. Purchasing an extension or larger bed would be a wise alternative.

The other dimension of the workpiece is how far off-centre it can be. This is known as the 'swing' ("The distance from the head center of a lathe to the bed or ways, or to the rest. The swing determines the diametric size of the object which is capable of being turned in the lathe; anything larger would interfere with the bed. This limit is called the swing of the bed. The swing of the rest is the size which will rotate above the rest, which lies upon the bed.")<ref>{{cite book |last1=Knight |first1=Edward H. |title=The Practical Dictionary of Mechanics |date=1875 |publisher=Cassell & co / Houghton Mifflin |location=London / U.S. |page=2469 [https://Mechanicalminds.org Mechanicalminds.org] }}</ref> from the notion that the work 'swings' from the centre upon which it is mounted. This makes more sense with odd-shaped work but as the lathe is most often used with cylindrical work, it is useful to know the maximum diameter of work the lathe will hold. This is simply the value of the swing (or centre height above the bed) multiplied by two. For some reason, in the U.S. swing is assumed to be diameter but this is incorrect. To be clear on size, it is better, therefore, to describe the dimension as 'centre height above the bed'. As parts of the lathe reduce capacity, measurements such as 'swing over cross slide' or other named parts can be found.

=== Varieties ===
{{more citations needed section|date=April 2014}}

The smallest lathes are "jewelers lathes" or "watchmaker lathes", which, though often small enough to be held in one hand are normally fastened to a bench.<ref>[https://www.csparks.com/watchmaking/Lathes.html Watchmaking Lathes] page by an amateur, describing and showing jewelers and watchmaker lathes and there usage (Sparks Communication website)</ref> There are rare and even smaller [[mini lathe]]s made for precision cutting.<ref name="microlathetokyo">{{cite web | url = https://www.designnews.com/automation-motion-control/tiny-lathe-produces-micro-parts/97554728735712 | author = Dennis Normile, Tokyo | title = The smallest micro lathe, made by researchers in Tokyo, Japan | accessdate = 2007-06-07 | publisher = designnews.com | date = 2001-07-16 | archive-date = 2019-11-04 | archive-url = https://web.archive.org/web/20191104014707/https://www.designnews.com/automation-motion-control/tiny-lathe-produces-micro-parts/97554728735712 | url-status = dead }}</ref> The workpieces machined on a jeweler's lathe are often metal, but other softer materials can also be machined. Jeweler's lathes can be used with hand-held "graver" tools or with a "compound rest" that attach to the lathe bed and allows the tool to be clamped in place and moved by a screw or lever feed. Graver tools are generally supported by a T-rest, not fixed to a cross slide or compound rest. The work is usually held in a collet, but high-precision 3 and 6-jaw chucks are also commonly employed. Common spindle bore sizes are 6&nbsp;mm,  8&nbsp;mm and 10&nbsp;mm. The term WW refers to the Webster/Whitcomb collet and lathe, invented by the American Watch Tool Company of Waltham, Massachusetts. Most lathes commonly referred to as watchmakers lathes are of this design. In 1909, the American Watch Tool company introduced the Magnus type collet (a 10-mm body size collet) using a lathe of the same basic design, the Webster/Whitcomb Magnus. (F.W.Derbyshire, Inc. retains the trade names Webster/Whitcomb and Magnus and still produces these collets.<ref>[https://www.mmsonline.com/suppliers/fw-derbyshire Trade names] on the F.W. Derbyshire company website</ref>) Two bed patterns are common: the WW (Webster Whitcomb) bed, a truncated triangular prism (found only on 8 and 10&nbsp;mm watchmakers' lathes); and the continental D-style bar bed (used on both 6&nbsp;mm and 8&nbsp;mm lathes by firms such as Lorch and Star). Other bed designs have been used, such as a triangular prism on some Boley 6.5&nbsp;mm lathes, and a V-edged bed on IME's 8&nbsp;mm lathes.

Smaller metalworking lathes that are larger than jewelers' lathes and can sit on a bench or table, but offer such features as tool holders and a screw-cutting gear train are called hobby lathes, and larger versions, "bench lathes" - this term also commonly applied to a special type of high-precision lathe used by toolmakers for one-off jobs.<ref>{{cite web|last1=Griffiths|first1=Tony|title=Makers of "Bench Precision" Lathes|url=http://www.lathes.co.uk/precision-bench-lathes-list|website=LATHES.CO.UK|access-date=5 February 2018|archive-url=https://web.archive.org/web/20171227132348/http://www.lathes.co.uk/precision-bench-lathes-list/|archive-date=27 December 2017|url-status=live|df=dmy-all}}</ref> Even larger lathes offering similar features for producing or modifying individual parts are called "engine lathes". Lathes of these types do not have additional integral features for repetitive production, but rather are used for individual part production or modification as the primary role.

Lathes of this size that are designed for mass manufacture, but not offering the versatile screw-cutting capabilities of the engine or bench lathe, are referred to as "second operation" lathes.

Lathes with a very large spindle bore and a chuck on both ends of the spindle are called "oil field lathes".

Fully automatic mechanical lathes, employing cams and gear trains for controlled movement, are called [[Automatic lathe#Screw machine|screw machine]]s.

Lathes that are controlled by a computer are [[Lathe (metal)#CNC lathe / CNC turning center|CNC lathes]].

Lathes with the spindle mounted in a vertical configuration, instead of horizontal configuration, are called vertical lathes or vertical boring machines. They are used where very large diameters must be turned, and the workpiece (comparatively) is not very long.

A lathe with a tool post that can rotate around a vertical axis, so as to present different tools towards the headstock (and the workpiece) are [[Lathe (metal)#Turret lathe|turret lathes]].<ref>Parker, Dana T. ''Building Victory: Aircraft Manufacturing in the Los Angeles Area in World War II,'' p. 81, 123, Cypress, CA, 2013. {{ISBN|978-0-9897906-0-4}}.</ref>

A lathe equipped with indexing plates, profile cutters, spiral or helical guides, etc., so as to enable [[ornamental turning]] is an [[#Ornamental turning|ornamental lathe]].

Various combinations are possible: for example, a vertical lathe can have CNC capabilities as well (such as a [[CNC VTL]]).

Lathes can be combined with other machine tools, such as a [[Drill#Drill press|drill press]] or [[milling machine|vertical milling machine]]. These are usually referred to as [[Lathe (metal)#Combination lathe|combination lathes]].