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Copyright 2000-2002 by Frank J. Hoose, Jr. Home
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Introduction: Introduction Terminology Glossary
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The author is not a professional machinist or engineer; no information provided herein represents professional advice or best practices. All information is provided to help hobbyists and other non-professionals gain a better understanding of the tools and techniques described.
Considerable care has been exercised to provide accurate and timely information. However the author cannot be responsible for information which is incorrect or out of date.
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All practices, procedures, modifications and product recommendations described herein are to be used at the discretion and risk of the reader.
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 workpiece along its axis and removes material from the workpiece 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 workpiece 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.
After learning some of the basic terminology of the lathe, check out the Capabilities and Features pages for lots more information.
To gain a good understanding of the lathe, you will need to know the names of the various components, as illustrated below. The carriage, in the circled area, consists of the apron, the vertical casting on which the carriage handwheel is mounted, and the saddle (not shown), the H-shaped casting that rides on the ways to which the apron is attached.
Animation courtesy of Enric del Rey and Latheworks, also check out this lathe group, en espanol
When comparing the size and working capacities of metal lathes there are several key dimensions to consider:
| Swing over bed | The diameter of the largest workpiece that can be rotated on the spindle without hitting the bed. This is the first of the two numbers used to describe the size of a metal lathe. In the case of the 7x10 or 7x12 lathes, it is 7". |
| Distance between centers | The longest piece of work that be held between a center in the headstock and a center in the tailstock. (see glossary below for more information). This is the second of the two numbers used to describe the lathe size. Based on this you would expect that a 7x10 would accomodate 10" between centers, a 7x12, 12" and a 7x14, 14". In fact, due to wishful marketing, the 7x10 is really only a 7x8. The 7x12 and 7x14 are what you would expect them to be. |
| Swing over the carriage | The diameter of the largest workpiece that can rotate over the carriage without hitting it. On the 7x lathes this is about 4" |
| Diameter of spindle through-hole | The diameter of the hole that passes through the spindle. On the 7x lathes (or any lathe having a #3 Morse Taper spindle) it is about 3/4". When facing relatively long stock, the free end of the stock can pass through the spindle if it is no larger than the through-hole diameter. |
Here's a table summarizing some of the dimensions for a 7x12 and 9x20 lathe:
| 7x12 | 9x20 | |
| Swing over bed | 7" | 9" |
| Distance between centers | 12" | 20" |
| Swing over carriage | 4" | 5" |
| Spindle Taper | #3MT | #3MT |
| Spindle through-hole diameter | 3/4" | 3/4" |
| Tailstock taper | #2MT | #2MT |
| Apron | Front part of the carriage assembly on which the carriage handwheel is mounted |
| Bed | Main supporting casting running the length of the lathe |
| Between Centers | 1. A dimension representing the
maximum length of a workpiece that can be turned between centers. A 7x10 lathe is 10"
between centers; a 7x12 lathe is 12" between centers. Lathe vendors sometimes
inaccurately represent this number. 2. A method of holding a workpiece by mounting it between a center in the headstock spindle and a center in the tailstock spindle (see Center). |
| Carriage | Assembly that moves the toolpost and cutting tool along the ways |
| Carriage Handwheel | A wheel with a handle used to move the carriage by hand by means of a rack and pinion drive |
| Center | A precision ground tapered cylinder with a 60º pointed tip and a Morse Taper shaft. Used in the tailstock to support the end of a long workpiece. May also be used in the headstock spindle to support work between centers at both ends. |
| Center Drill | 1. A short, stubby drill used to
form a pilot hole for drilling and a shallow countersunk hole for mounting the end of a
workpiece on a center. 2. The process of drilling a workpiece with a center drill |
| Centerline | An imaginary line extending from the center of the spindle through the center of the tailstock ram, representing the central axis of the lathe around which the work rotates. |
| Chuck | A clamping device for holding work in the lathe or for holding drills in the tailstock. |
| Compound | Movable platform on which the toolpost is mounted; can be set at an angle to the workpiece. Also known as the compound slide and compound rest. |
| Compound Handwheel | A wheel with a handle used to move the compound slide in and out. Also known as the compound feed. |
| Cross-slide | Platform that moves perpendicular to the lathe axis under control of the cross-slide handwheel |
| Cross-slide Handwheel | A wheel with a handle used to move the cross-slide in and out. Also known as the cross feed. |
| Dog (or dogleg) | An "L"-shaped adapator, usually made of cast iron, with a hole for the workpiece and locking bolt in the short end. Used to clamp a workpiece and apply rotational force to it while the workpiece is mounted between centers along with a faceplate. The dog engages with a hole in the faceplate to apply the force to the workpiece. Used in place of a chuck, especially in pre-1940's work, and/or when tapers are cut by offsetting the tailstock. |
| Faceplate | A metal plate with a flat face that is mounted on the lathe spindle to hold irregularly shaped work. |
| Facing | A lathe operation in which metal is removed from the end of workpiece to create a smooth perpendicular surface, or face. |
| Gib | A length of steel or brass with a diamond-shaped cross-section that engages with one side of dovetail and can be adjusted by means of screws to take up any slack in the dovetail slide. Used to adjust the dovetail for optimum tightness and to compensate for wear. |
| Halfnut | A nut formed from two halves which clamp around the leadscrew under control of the halfnut lever to move the carriage under power driven from the leadscrew. |
| Halfnut Lever | Lever to engage the carriage with the leadscrew 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. |
| Leadscrew | Precision screw that runs the length of the bed. Used to drive the carriage under power for turning and thread cutting operations. Smaller leadscrews are used within the cross-slide and compound to move those parts by precise amounts. |
| Morse Taper | A taper of specific dimensions used to mate matching male and female parts such that they lock together tightly and concentrically. Tapers are of various sizes such as #0, #1, #2, #3, etc. with larger numbers representing larger sizes. The spindle of the mini-lathe has a #3 Morse Taper and the tailstock ram has a #2 Morse Taper. |
| Saddle | A casting, shaped like an "H" when viewed from above, which rides along the ways. Along with the apron, it is one of the two main components that make up the carriage. |
| 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. |
| Spindle Through-hole | A dimension indicating the minimum diameter of the hole that passes through the spindle. A workpiece with a diameter smaller than this can pass through the spindle to facilitate working on long pieces of work. On the minilathe it is 3/4" but can safely be reamed out to 13/16" |
| Swing | A dimension representing the largest diameter workpiece that a lathe can rotate. The 7x10 or 7x12 mini-lathe has a 7" swing, meaning that the maximum size workpiece that can rotate without hitting the bed is 7" in diameter. |
| 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 Handwheel | A wheel with a handle used to move the tailstock ram in and out of the tailstock casting. |
| Tailstock Ram | A piston-type shaft that can be moved in and out of the tailstock by turning the tailstock handwheel. Has a tapered internal bore to accept a #2 Morse Taper shank |
| Tool | A cutting tool used to remove metal from a workpiece; usually made of High Speed Steel or carbide. |
| Tool Blank | A piece of High Speed Steel from which a cutting tool is ground on a bench grinder. Typically 5/16" square by 2 1/2" long for mini-lathe use. |
| Toolpost | A holding device mounted on the compound into which the cutting tool is clamped |
| Turning | A lathe operation in which metal is removed from the outside diameter of the workpiece, thus reducing its diameter to a desired size. |
| 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. |
Mini-Lathe Mini-Mill Bandsaw Grinder Anodizing Lapping Links Safety Premium Content
Mini-lathe: Accessories Adjustments Capabilities Chucks Dial Indicators Features
Getting Started Glossary
Introduction Materials Modifications My Shop Operation
Reviews Sieg
Factory Tool Grinding
Troubleshooting Tuning Versions