A small metal lathe opens up a whole workshop: bushes, spacers, pins, knobs, threaded parts, model engineering and repairs that would otherwise mean a trip to a machine shop. Most first lathes in UK home workshops are Chinese-made benchtop machines sold under several names. They share a handful of basic designs, so once you understand the size codes and the few things that really differ, choosing one gets much easier. This guide covers the common sizes, what the numbers mean, change gears versus a gearbox, and the checks and upgrades that turn a new lathe into an accurate one.

What Swing and Between Centres Mean

Lathe sizes are usually given as two numbers, such as 7x14. The naming comes from inches and is nominal, so treat it as a class name rather than an exact measurement.

  • Swing over bed (the first number) is the largest diameter that will turn without hitting the bed. A "7 inch" lathe swings about 180 mm.
  • Swing over cross-slide is the largest diameter that clears the carriage and cross-slide. It is much smaller, and it is the limit for anything long enough to need the carriage underneath it. Check this figure, not just the headline swing.
  • Distance between centres (the second number) is the longest part you can hold between a centre in the spindle and a centre in the tailstock. With a chuck fitted and a drill chuck in the tailstock, the usable length is a good deal shorter.
  • Spindle bore is the hole through the spindle. It limits the bar you can pass through the headstock, which matters when you make many small parts from long bar.
Headstock Tailstock Distance between centres Cross-slide centre height less above slide
Swing is twice the centre height, so the cross-slide limits long work much more than the bed does.

The Common Size Classes

Figures below are typical for each class. Different sellers' versions of the "same" lathe vary, so check the actual specification sheet of the machine you are looking at.

Class Approx. swing × centres Typical features Suits
7x10, 7x12, 7x14 mini lathe 180 mm × 250 / 300 / 350 mm Variable-speed DC motor (brushed on older types, brushless on newer ones), change gears, compound slide, MT3 spindle and MT2 tailstock on most versions, 80 to 100 mm three-jaw chuck, about 40 kg. Small parts, model engineering, hobby repairs. Fits on a normal bench and can be carried by two people.
Longer mini lathes (7x16 and similar) 180 mm × 400 mm Same headstock, longer bed. Some have larger motors. When you need length more than diameter.
8x16 class About 210 mm × 400 mm A step up in bed width, spindle and motor; often brushless with a digital speed readout. Owners who want more stiffness without a big floor-standing lathe.
9x20 class About 230 mm × 500 mm Long-established design: belt-and-pulley speed changes, change gears, heavier bed. Sold under many brands over the years. Longer and larger work on a budget; second-hand examples are common.
280 mm swing class About 280 mm × 600 to 700 mm Geared head or belt drive, often a screw-cutting gearbox, larger spindle bore, usually on a stand. Well over 100 kg. A "lathe for life" if you have the space, a solid floor and the means to move it.

In the UK these designs are sold by several suppliers under their own names, for example Sieg-made mini lathes through various dealers and Warco's own range (such as the WM180 and WM250). Some dealers offer pre-delivery checking and adjusting, often called "fettling", which is worth asking about. Specifications and model names change, so compare current spec sheets rather than relying on forum posts from years ago.

How to Choose the Size

  • List the five biggest jobs you can imagine. If they all fit within about 50 mm diameter and 150 mm long, a 7x mini lathe will do. If you want to turn 100 mm flywheels, long shafts or cast iron in quantity, go bigger.
  • Bigger is stiffer. A heavier lathe takes deeper cuts with less chatter and holds size better. A mini lathe can make accurate parts, but with lighter cuts and more patience.
  • Small parts on a big lathe are fine; big parts on a small lathe are not. If space and money allow, most people do not regret going up a size.
  • Count the cost of tooling. Chucks, a quick-change tool post, tool holders, drills, centres, a dial indicator and measuring tools can cost a good share of the lathe price.
  • Think about the floor and the stairs. A mini lathe goes up a flight of stairs; a 280-class lathe needs an engine crane or several strong friends.

Change Gears vs a Screw-Cutting Gearbox

To cut threads and use power feed, the carriage is driven along the bed by the lead screw, geared to the spindle. The ratio sets the feed per revolution and the thread pitch.

  • Change gears are a set of loose gears you swap on a slotted arm (the banjo). They are cheap, simple and very flexible: with the right gears you can cut almost any pitch. The downside is time, since each change means loosening the banjo and setting the mesh again.
  • A screw-cutting (Norton) gearbox lets you choose pitches and feeds with levers. It is common on 280-class lathes and above. Most gearboxes still need a change of the end gears for some pitches, especially imperial threads on a metric lathe or the other way round.

Mini lathes use change gears. The gear set that comes in the box covers the common metric and imperial pitches, and the lathe's chart shows which gears go where. A metric lathe cuts exact imperial threads with a 127-tooth gear (because 127 × 0.2 mm = 25.4 mm, one inch), or very close approximations from the standard set. The Lathe Change Gear Calculator works out gear trains from your own set, shows the pitch error and checks that the gears will physically fit.

Once you know the gears, the Lathe Threading Pass Calculator gives a pass-by-pass depth list so the load stays even. For screw-cutting inside a bore, see the Internal Threading Guide, and check sizes against the Thread Size Chart.

Motor and Speed Range

Mini lathes use a variable-speed DC motor, either brushed with a control board or, on newer models, brushless. Many have a high/low gear range: low for torque on larger diameters and threading, high for small diameters. A brushless motor generally keeps more torque at low speed, which helps when screw-cutting or turning larger work. Lathes without a low range rely on the motor's low-speed torque alone, so check the low-speed figure if you plan to thread a lot.

Larger lathes may use an induction motor with belts or a geared head; some have an inverter for variable speed. For the right spindle speed for a material and diameter, see the Surface Speed Guide, and remember that small lathes usually run below the ideal speed on large diameters, which is fine.

Set-Up Checks on a New Lathe

A new budget lathe is a kit of well-made parts that usually needs adjusting. Doing these checks in the first weekend makes a bigger difference to accuracy than any upgrade.

First-weekend checklist

  1. Clean off the shipping grease from every sliding surface and the lead screw with paraffin or a degreaser, then oil all the ways, screws and oil points.
  2. Bolt it to a stiff bench. A lathe bed can twist if bolted down on an uneven surface. Shim under the feet so the bed is not strained.
  3. Adjust the gib strips on the cross-slide, compound and carriage so they move smoothly with no rocking. Tighten each gib screw a little at a time and lock the nuts.
  4. Check the change gears run with a small gap. Setting the mesh with a strip of paper between the teeth is a common method.
  5. Check chuck run-out with a dial indicator on a ground bar or the chuck body. A few hundredths of a millimetre is normal for a three-jaw chuck; a four-jaw lets you get closer.
  6. Do a two-collar test. Turn a bar with two collars some distance apart in one pass setting, then measure both. A difference means the headstock is not parallel to the bed or the bed is twisted. Shim the bed or adjust the headstock until they match.
  7. Align the tailstock by turning between centres and measuring both ends, or with a test bar and dial indicator, then adjust the tailstock set-over screws.
  8. Check the electrics and guards: the chuck guard switch, emergency stop and earth. Never leave the chuck key in the chuck.

The Usual Upgrades

Owners of the popular mini lathes have improved them for years, and the same upgrades come up again and again:

  • Quick-change tool post (QCTP): the most popular upgrade. Tools are pre-set to centre height, so changing tools takes seconds. Buy the size made for mini lathes.
  • Metal gears: some mini lathes use plastic gears in the headstock or change gear train. They are designed to break first in a crash, but many owners replace them with steel gears.
  • Carriage lock: lets you lock the carriage for facing and parting, which cuts chatter.
  • Four-jaw independent chuck and faceplate for odd shapes and accurate centring.
  • Collet chuck: ER collets or 5C hold small round bar accurately and quickly; see Mastering the Collet and the ER Collet Size Chart.
  • Digital readouts (DRO) on the cross-slide and carriage, which save counting dial turns and allowing for backlash.
  • A stiffer compound or a solid tool post block in place of the compound for heavier cuts.
  • Steady and travelling rests for long, thin parts.

For cutting tools, start with a set of brazed or indexable carbide tools plus a few high-speed steel blanks you can grind yourself. Small lathes often work better with sharp, positive-rake inserts meant for aluminium or light cuts. The Carbide Insert Designation Chart decodes insert codes, and Defeating Stringy Swarf covers chip control. The Machine Taper Chart helps when buying centres and arbors for the spindle and tailstock tapers, and the Taper Calculator sets the compound for tapers.

Safety Basics

  • No gloves, loose sleeves, ties or long hair near the turning chuck. Wear eye protection always.
  • Take the chuck key out every time, without exception.
  • Do not hold emery cloth around work with your fingers wrapped round it; use a backing stick.
  • Run the spindle at low speed first after fitting new work or a new chuck.
  • Use a brush or hook for swarf, never your hand.

Threading on Your New Lathe

Free calculators that run in your browser.

Change Gear Calculator Threading Pass Calculator

Frequently Asked Questions

What does 7x14 mean on a mini lathe?

The first number is the nominal swing over the bed in inches (about 180 mm), the largest diameter that clears the bed. The second is the nominal distance between centres in inches (about 350 mm), the longest part you can hold between a headstock centre and a tailstock centre. Real capacities are a little smaller, and the swing over the cross-slide is much smaller.

Can a mini lathe cut threads?

Yes. Mini lathes cut threads by gearing the lead screw to the spindle with change gears. A metric lathe can cut most imperial threads with a 127-tooth gear or a close approximation from its standard set. The Lathe Change Gear Calculator works out the gears for your machine.

Is a 7x14 mini lathe big enough?

For model engineering, small parts, bushes, pins, knobs and repairs on bikes, clocks and small engines, yes. It is too light for heavy cuts in steel bar over about 50 mm diameter, long shafts or large flywheels. If you know you need bigger work, a 9x20 or 280-class lathe is worth the extra space and weight.

Is a gearbox worth paying for?

If you cut many different threads or change feed rates often, yes. A screw-cutting gearbox lets you change pitch with levers. Change gears do the same job for less money, but each change means swapping gears on the banjo.

What should I check on a new mini lathe?

Clean off the shipping grease, check the gibs and adjust out any slop, bolt the lathe to a stiff bench without twisting the bed, check that the headstock turns parallel with a two-collar test, align the tailstock, check chuck run-out and oil everything before the first cut.

Summary

Pick the size from the work you will do: a 7x mini lathe for small parts and model work, an 8x16 or 9x20 for more stiffness and length, and a 280-class machine if you have the space for a lathe for life. Check swing over the cross-slide, not just over the bed. Change gears are fine for most hobby threading, and the Change Gear Calculator takes the maths out of it. Whatever you buy, spend the first weekend cleaning, adjusting and checking alignment before chasing upgrades.