Swing vs Distance Between Centers on Wood Lathes

A lathe's two capacity numbers tell you completely different things about what you can make. Understanding which one matters for your project saves you from discovering limitations mid-turn.

Every wood lathe advertisement lists two measurements: swing and distance between centers. A typical midi lathe might claim "12-inch swing, 20 inches between centers." These aren't interchangeable ways of describing size. They define completely different limitations that constrain different types of work.

What Swing Actually Measures

Swing describes the maximum diameter of workpiece that will clear the lathe bed when spinning. Specifically, it's twice the distance from the center of the spindle to the nearest obstruction, which is usually the lathe bed itself.

A lathe with 12-inch swing has 6 inches of clearance between the spindle centerline and the bed. Mount a 12-inch diameter bowl blank on the faceplate and the bottom edge will just barely clear the bed as it spins. Try a 13-inch blank and it hits the bed every revolution.

This measurement matters most for faceplate work like bowls, platters, and anything mounted perpendicular to the lathe's axis. The blank's diameter determines whether it physically fits.

The confusion starts because swing gets measured in different ways depending on what obstruction you're measuring to. Over the bed swing is the full capacity when nothing else is in the way. Over the tool rest swing accounts for the tool rest assembly sitting on the ways, which reduces usable diameter. Some manufacturers list both numbers, others only list the larger over-bed measurement.

A lathe with 12.5-inch swing over the bed might have only 9.5-inch swing over the tool rest. That 3-inch difference matters when you're working at the lathe's capacity limits. You can mount a 12-inch blank, but you can only work on it by removing the tool rest or positioning it elsewhere.

Distance Between Centers Explained

Distance between centers measures how far apart the headstock and tailstock can be positioned. It defines the maximum length of workpiece you can mount between centers - spindles, table legs, chair legs, bed posts, and any other work held lengthwise.

A lathe with 20 inches between centers can accommodate a workpiece up to about 19.5 inches long. You lose about half an inch because the spur center and live center each protrude into the workpiece ends. The exact loss depends on the specific centers you're using.

This measurement only matters for spindle work. Bowl turning and faceplate work don't use the tailstock at all, so distance between centers becomes irrelevant. You could have 6 inches or 60 inches between centers and it wouldn't change what bowls you can turn.

The distinction trips up first-time lathe buyers who see "12 x 20" and assume both numbers describe general capacity. They're actually describing capacity for two completely different types of work that don't overlap much.

How Bed Length Changes Things

Distance between centers connects directly to bed length, but they're not identical. The bed needs to be longer than the distance between centers to allow the tailstock to move along its full range while still having enough bed to support it.

A lathe with 20 inches between centers might have a 26-inch bed. The extra 6 inches provides support structure for the tailstock when it's positioned at maximum extension. Some of this extra length sits beyond the headstock too, providing mounting points for the machine.

Some lathes allow you to rotate the headstock outboard, mounting large diameter work off the end of the bed entirely. This lets you turn bowls or platters larger than the advertised swing capacity. A 12-inch swing lathe might handle 18 or 20-inch diameter bowls outboard.

Working outboard creates new challenges. The workpiece hangs off one side of the lathe, making the machine want to tip toward that side. You need substantial ballast or floor mounting to keep things stable. The machine's weight becomes even more critical when working outboard with large diameter pieces. The tool rest positions differently too, often requiring custom rests or adapters.

What Mini Lathes Sacrifice

Mini lathes typically offer something like 8 to 10-inch swing and 12 to 18 inches between centers. These machines make spindle work practical but limit bowl turning to small projects.

An 8-inch swing means 4 inches of clearance from spindle to bed. You can mount an 8-inch blank, but working it becomes awkward because the tool rest can't get close to the wood without the blank hitting it. Practical bowl diameter tops out around 6 or 7 inches.

The short distance between centers restricts spindle work too. Turning table legs for a coffee table works fine at 16 inches. Turning legs for a dining table at 28 inches isn't possible. Bed posts, long architectural spindles, and furniture components for full-size pieces require longer capacity.

Mini lathes excel at small-scale work where their limitations don't matter. Pen turning, tool handle making, small decorative spindles, bottle stoppers, and similar projects fit comfortably within their capacity. Try to expand beyond that and you hit the walls quickly.

Midi Lathe Sweet Spot

Midi lathes usually offer 12 to 14-inch swing and 16 to 22 inches between centers. This combination handles a much wider range of projects than the numbers might suggest.

A 12-inch swing accommodates bowl blanks up to about 10 inches in practical working diameter. That covers salad bowls, fruit bowls, serving bowls, and most decorative bowl projects. You only need larger capacity for platters or statement pieces.

The 20-inch distance between centers handles most furniture spindles. Chair legs, table legs for coffee tables and end tables, and architectural trim pieces all fit. You're limited on dining table legs and bed components, but the majority of spindle work falls within range.

This capacity level suits hobbyists and small professionals who need versatility without requiring a machine that weighs 500 pounds and dominates a workshop. The midi lathe category exists specifically to hit this practical sweet spot for general woodworking applications.

Some midi lathes offer bed extension kits that add another 20 to 30 inches of distance between centers. A 20-inch lathe becomes a 43-inch lathe with the extension, opening up much longer spindle work without requiring a full-size machine all the time.

Full Size Lathe Capacity

Full-size lathes start around 16-inch swing and 40 inches between centers. Professional models push to 22-inch swing and 42 to 60 inches or more between centers.

The larger swing matters primarily for production bowl turners who regularly work with substantial blanks. A 20-inch swing handles blanks up to about 18 inches in working diameter, which covers large serving platters, decorative bowls, and architectural pieces.

The extended distance between centers opens up long spindle work that smaller machines can't touch. Dining table legs at 28 to 30 inches, bed posts, stair newels, and architectural columns all become possible. Production furniture makers need this capacity.

These machines also tend to have more robust construction throughout. Heavier beds, larger spindles, more powerful motors, and beefier bearings. The capacity numbers reflect what you can fit, but the structural beef reflects what you can actually work on effectively at those sizes.

Swing Over the Gap

Some full-size lathes include a section of removable bed near the headstock called a gap. With this section removed, you can mount larger diameter work directly on the headstock where the bed doesn't restrict diameter.

A 16-inch swing lathe with a gap might offer 24-inch capacity over the gap. This lets you rough out large bowl blanks, then remount them on a smaller faceplate to finish them within the normal swing capacity.

The gap limits how much of the bowl you can work on in one mounting. You can hollow the center and shape the outside, but you can't reach all the way to the edge if the blank exceeds normal swing. Most turners use gap capacity for initial roughing, then work within standard swing for finishing.

Gaps also reduce bed rigidity in that section. The bed becomes effectively shorter for spindle work because you can't use the tool rest over the gap area. This matters less for bowl work where you're not using that section of the bed anyway.

How Swing Affects Tool Access

The practical limitation isn't just whether a blank physically fits. It's whether you can get your tools into position to work on it effectively.

Mount a 12-inch blank on a lathe with 12-inch swing and the outer edge comes within fractions of an inch of the bed. Your tool rest can barely squeeze in there. Moving the tool rest back away from the work means extended tool reach, which creates leverage and chatter problems.

Most turners consider practical capacity to be about 80 percent of advertised swing. A 12-inch swing lathe works comfortably with blanks up to 9 or 10 inches. You have clearance to position tools properly without fighting interference.

The same logic applies to distance between centers. A 20-inch capacity lathe works well with 18-inch spindles. You want clearance at both ends to position centers without fighting the machine's limits.

Variable Speed and Capacity Relationship

Larger capacity usually requires lower maximum speeds. A 10-inch bowl blank at 1200 RPM creates significant centrifugal force. A 20-inch blank at that same speed generates four times the force because the outer edge moves so much faster.

Mini lathes with 8-inch swing often run up to 3000 or 4000 RPM because small work benefits from high speed for smooth cuts. Full-size lathes with 20-inch swing typically max out around 1200 to 1800 RPM because higher speeds become dangerous with large diameter work.

The variable speed system lets you dial in appropriate RPM for whatever size blank you're working on. Small spindles might run at 2000 RPM. Large bowls might run at 300 RPM during roughing, then speed up to 800 RPM for finishing.

Electronic variable speed lathes provide the smoothest speed adjustment across the full range. Mechanical pulley systems work but require stopping the lathe to change belts. This matters more when capacity encourages working with a wide range of blank sizes that need different speeds.

Indexing and Both Measurements

Indexing lets you lock the spindle at specific angular positions to make flutes, reeds, or decorative patterns. This feature interacts with both capacity measurements in different ways.

For spindle work, you need adequate distance between centers to accommodate the workpiece, then sufficient swing to allow cutting tools to reach the work without hitting the bed while the piece is positioned at various index points.

For bowl work, indexing primarily relates to swing because you're working within that diameter constraint. The distance between centers doesn't factor in since bowls don't use the tailstock.

Indexing positions typically divide the rotation into 24, 36, or more segments. More positions provide finer control for detailed decorative work. This becomes a distinct feature from capacity measurements but works within the constraints those measurements define.

Bed Extension Trade-offs

Adding bed extensions to increase distance between centers seems like an easy capacity upgrade. Many manufacturers offer extensions for their midi lathes specifically to provide this flexibility.

Extensions work well for occasional long spindle work. You can turn table legs beyond the base capacity when needed, then remove the extension for regular work that doesn't need the extra length.

The extension adds weight and takes up additional floor space even when not in use. The connection point between original bed and extension can introduce flex or alignment issues if not properly supported. Some turners build auxiliary floor supports under long extensions to prevent sagging.

Extended beds also move the lathe's center of gravity. A midi lathe with a 20-inch extension becomes front-heavy, more prone to tipping if you mount a large diameter blank outboard. The floor space requirements double or triple depending on extension length.

What Matters for Your Work

Bowl turners prioritize swing capacity. Distance between centers matters less because they rarely work between centers. A 14-inch swing lathe with only 16 inches between centers suits a dedicated bowl turner fine.

Spindle turners prioritize distance between centers. Swing only needs to be large enough to clear the spindle diameter plus tool access. A 10-inch swing lathe with 40 inches between centers fits a furniture maker perfectly.

Mixed work requires balancing both measurements. A 12-inch swing with 20 to 24 inches between centers covers most general woodturning without requiring a massive machine. This describes most midi lathes specifically because that combination serves the broadest range of users.

Production turners often end up with multiple machines. A small lathe for pen work and small spindles. A large lathe for bowls and platters. A long-bed lathe for furniture components. Each machine optimized for specific work rather than trying to make one machine handle everything. Like other power tools in a professional shop, having the right capacity for each task produces better results than forcing one machine to do everything.

Reading the Specifications Right

Manufacturer specs sometimes obscure the real numbers. "12-inch swing" might be measured over bed, over gap, over tool rest, or over some theoretical point that doesn't match actual working conditions.

Distance between centers sometimes gets listed as bed length, which is longer than usable capacity. A 36-inch bed might only provide 28 inches between centers once you account for headstock and tailstock positioning.

The reliable approach involves checking multiple specification sources and reading what other turners report about actual capacity. Forums and reviews from users often provide more accurate practical capacity numbers than manufacturer marketing materials.

Photos showing the machine with various size blanks mounted provide useful reality checks. If all the marketing photos show 6-inch bowls on a "12-inch swing" lathe, that suggests practical capacity runs smaller than advertised.

Capacity and Workshop Space

Capacity measurements directly determine the machine's footprint. A lathe with 40 inches between centers needs at least 48 inches of linear space, probably 54 inches to allow comfortable access to the tailstock end.

Swing capacity affects width requirements. A 16-inch swing lathe with outboard turning capability needs clear space to the side for mounting and working on large diameter pieces.

You also need access space around the lathe. Working a 20-inch diameter bowl blank requires you to move completely around the machine as you shape different sections. The machine might only be 24 inches wide, but you need 4 to 5 feet of clear space on the outboard side.

The specifications tell you what fits on the lathe. The workshop reality tells you whether the lathe fits in your space. These aren't always the same answer.