What Is a Jointer Used for in Woodworking: Complete Guide to Perfect Edges

Key Takeaways

• A jointer creates perfectly flat surfaces and square edges on lumber, essential for professional woodworking projects

• Face jointing removes warps, twists, and cups from board faces, creating a true reference surface

• Edge jointing produces 90-degree angles necessary for seamless glue-ups and panel construction

• Jointers work differently than planers - jointers flatten while planers create parallel surfaces

• Spiral cutterheads significantly improve cut quality, reduce noise, and last longer than straight knives

• Proper setup and technique are crucial for safety and achieving professional results

Introduction

If you've ever struggled with boards that rock on your workbench, gaps in your glue-ups, or lumber that just won't sit flat no matter how much you sand it, you're experiencing exactly why what is a jointer used for in woodworking is such a fundamental question for anyone serious about the craft. After twenty years of professional woodworking and teaching countless students, I can confidently say that understanding and mastering the jointer transforms amateur work into professional-quality projects.

The jointer stands as one of the most misunderstood tools in the workshop, often confused with planers or dismissed as unnecessary by beginners who haven't yet experienced the frustration of working with twisted, cupped, or bowed lumber. Yet this machine performs a function that no other tool can replicate effectively - creating a perfectly flat reference surface from which all other dimensions and cuts are measured.

Understanding What a Jointer Does in Woodworking

At its core, what does a jointer do in woodworking comes down to one essential function: removing material from the high spots of a board to create a perfectly flat surface. While this sounds simple, the implications for your woodworking are profound. Every accurate cut, every tight joint, and every professional-looking project starts with lumber that has at least one true, flat face.

Think of rough lumber like a piece of land with hills and valleys. The jointer acts like a bulldozer that levels only the high spots, gradually creating a flat plane across the entire surface. Unlike hand planes that follow the existing contours of the wood, or sanders that simply smooth what's already there, the jointer references its own precision-machined tables to create true flatness regardless of the board's initial condition.

The magic happens through the relationship between three critical components: the infeed table, the cutterhead, and the outfeed table. The infeed table is set slightly lower than the cutting circle of the knives, determining how much material gets removed with each pass. The outfeed table aligns perfectly with the top of the cutting arc, supporting the newly jointed surface as it exits the cutterhead.

The Anatomy of a Woodworking Jointer

Understanding what is a jointer woodworking machine requires examining its key components and how they work together to achieve those perfect surfaces we're after. Each element plays a crucial role in the jointing process, and knowing their functions helps you use the tool more effectively and troubleshoot problems when they arise.

The infeed and outfeed tables form the foundation of any jointer. These precisely machined surfaces must be perfectly coplanar (in the same plane) for the jointer to work correctly. The infeed table adjusts up and down to control the depth of cut, typically ranging from 1/32" to 1/8" per pass. The outfeed table generally remains fixed at the height of the cutting circle, though some models allow fine adjustment for knife changes.

The fence guides your workpiece and determines the angle of your edge joints. A good fence should be sturdy, perfectly straight, and easily adjustable from 90 to 45 degrees. Many woodworkers spend considerable time ensuring their fence is exactly 90 degrees to the tables, as even a fraction of a degree off square compounds across multiple boards in a glue-up.

The cutterhead is truly the heart of the jointer. Traditional jointers use straight knives - essentially long, sharp blades that span the width of the cutterhead. However, many modern woodworkers are upgrading to spiral cutterheads like those offered by Sheartak, which feature dozens of small, square carbide inserts arranged in a spiral pattern. These provide numerous advantages:

• Quieter operation - the spiral arrangement creates a shearing cut rather than a chopping action

• Better finish quality - especially on figured or difficult grain

• Longer lasting - carbide inserts can be rotated four times before replacement

• Easier maintenance - no knife setting required, just loosen, rotate, and retighten

• Reduced tear-out - the shearing action handles reversing grain beautifully

Primary Functions: Face Jointing and Edge Jointing

Face Jointing: Creating Your Reference Surface

Face jointing addresses the most common lumber defects: cup, bow, twist, and warp. When you understand what does a jointer do woodworking projects, you realize it's about establishing that crucial first reference surface from which all other operations proceed.

I always tell my students to think of face jointing like building a house - you need a solid, level foundation before anything else can be properly constructed. Place a cupped board on your table saw, and it will rock during the cut, producing an edge that's anything but straight. Run that same board through your planer without jointing first, and you'll simply create a thinner cupped board, as the planer's feed rollers press the cup flat temporarily, only for it to spring back once released.

The technique for face jointing requires understanding grain direction and applying appropriate pressure. Start with the concave side down if the board is cupped - this provides more stable support. Apply pressure primarily over the infeed table at the beginning of the cut, then transfer that pressure to the outfeed table as soon as enough wood has passed the cutterhead. This transfer of pressure is crucial

Edge Jointing: Preparing for Perfect Glue-Ups

Edge jointing serves a different but equally critical purpose in answering what is a jointer for woodworking - it creates perfectly straight, square edges essential for invisible glue lines in panel construction. Even boards that appear straight from the lumberyard rarely have edges suitable for gluing without jointing.

The process seems straightforward: run the edge across the jointer with the previously jointed face against the fence. However, achieving consistently perfect results requires attention to several factors. First, ensure your fence is exactly 90 degrees to the table - even being off by half a degree creates gaps in your glue-ups. Second, maintain consistent pressure against both the fence and the table throughout the cut. Any wobble or drift introduces curves or angles into your edge.

Tips for successful edge jointing:

• Check fence squareness before every critical glue-up

• Use a push stick for boards under 3 inches wide for safety

• Joint mating edges in opposite directions to cancel out any minor fence angle errors

• Take light passes - forcing thick cuts often causes boards to drift from the fence

• Mark your boards to track which edges have been jointed

Jointer vs. Planer: Understanding the Difference

The confusion between jointers and planers represents one of the biggest misunderstandings in woodworking. While both machines remove material to improve lumber, understanding what is a jointer in woodworking versus what a planer does reveals why most serious woodworkers consider both essential.

A jointer creates one flat face without reference to any other surface. It doesn't care about thickness or parallelism - its only job is flatness. Feed a 2-inch thick twisted board through a jointer repeatedly, and you'll eventually have a very thin but perfectly flat board. The jointer removes material wherever it's high, regardless of what that does to overall thickness.

A planer, conversely, creates parallel surfaces. It references the bottom face of your board against its bed and cuts the top face parallel to it. Feed that same twisted board through a planer, and you'll get a uniformly thick but still twisted board. The planer's pressure rollers temporarily flatten the board during cutting, but the twist returns once it exits the machine.

This fundamental difference explains why the typical workflow moves from jointer to planer. First, create one flat face on the jointer. Then, with that flat face against the planer bed, create a parallel face at your desired thickness. This one-two combination produces lumber that's both flat and uniformly thick - the foundation for furniture-quality work.

Choosing the Right Jointer Size

When exploring what is a woodworking jointer that's right for your shop, size becomes a critical consideration. Jointer size primarily refers to the width of the cutting capacity - how wide a board you can joint in a single pass. Common sizes range from 6-inch benchtop models to 12-inch or wider industrial machines.

The 6-inch jointer represents the entry point for most serious hobbyists. It handles the majority of furniture-making tasks, as you can joint boards up to 6 inches wide and face joint boards of any width by taking multiple passes. These jointers work well in smaller shops and often feature excellent upgrade options like Sheartak's 6-inch spiral cutterheads that dramatically improve their performance.

Eight-inch jointers offer significantly more capacity while still fitting in most home workshops. The extra 2 inches of width might not sound like much, but it makes a huge difference when working with wider boards. You'll spend less time ripping boards to fit your jointer capacity and more time actually woodworking. The longer tables typically found on 8-inch models also improve accuracy when jointing longer boards.

Factors to consider when choosing jointer size:

• Available space - remember to account for infeed and outfeed clearance

• Power requirements - larger jointers need 220V power

• Types of projects - furniture makers might manage with 6-inch, while those building doors need larger

• Budget - price increases significantly with size

• Upgrade potential - consider models that accept spiral cutterhead upgrades

Setting Up Your Jointer for Optimal Performance

Proper setup determines whether your jointer produces furniture-grade results or frustrating problems. Understanding what does a jointer do in woodworking means nothing if the machine isn't properly calibrated and maintained.

Start with table alignment. Using a high-quality straightedge, check that your infeed and outfeed tables are coplanar when the infeed is raised to the same height as the outfeed. Any twist or misalignment here affects every board you joint. Most quality jointers provide adjustment mechanisms, though the process requires patience and precision.

Knife height setting on traditional straight-knife jointers demands particular attention. Each knife must be set to exactly the same height and perfectly parallel to the tables. The traditional method uses a dial indicator, though magnetic knife-setting jigs have simplified this process considerably. Even a few thousandths of an inch difference in knife height causes ridges, snipe, or tapered cuts.

The fence setup often gets overlooked but proves equally critical. Beyond ensuring it's square to the tables, check that it's straight along its entire length and that it locks solidly without shifting. A fence that flexes under pressure or isn't perfectly straight makes accurate edge jointing impossible. Many woodworkers upgrade to aftermarket fences for improved rigidity and precision.

Critical setup checkpoints:

• Tables must be coplanar within 0.002" across their length

• Knives should be within 0.001" of each other in height

• Fence squareness should be checked with a precision square, not a combination square

• Outfeed table height must match the cutting circle exactly

• All adjustment locks must hold solidly without shifting

Advanced Jointing Techniques

Once you master basic operations, understanding what is a jointer woodworking tool capable of opens up advanced techniques that expand its utility beyond simple edge and face preparation.

Spring joints - intentionally creating a slight hollow in the center of an edge - improve glue-up strength in long boards. By applying slight pressure in the middle of the board during edge jointing, you create a gap of about 1/32" that closes under clamping pressure. This technique ensures the ends of your boards stay tight even as wood movement occurs over time.

Jointing thin stock requires special techniques since pieces under 1/4" thick can slip under the guard and into the cutterhead. Create a auxiliary bed from melamine or MDF that raises the work surface, reducing the gap at the cutterhead. Some woodworkers also use specialized push blocks that hold thin pieces securely while keeping hands safe.

Tapering on the jointer offers more control than table saw tapering jigs for certain operations. By starting the cut partway down the board and taking progressively longer passes, you can create controlled tapers for table legs or other furniture components. This technique requires practice but produces smooth, accurate tapers without special jigs.

Maintaining Your Jointer for Long-Term Performance

Regular maintenance keeps your jointer performing at its peak while extending its life significantly. Understanding what is a jointer for woodworking includes knowing how to keep it in prime condition for years of reliable service.

Daily maintenance involves simply brushing or vacuuming chips from the tables and keeping the surfaces clean. Apply paste wax to the tables monthly to prevent rust and help boards glide smoothly. Avoid silicone sprays that can contaminate wood and interfere with finishes. Check fence squareness weekly if you do critical edge jointing, as vibration can gradually shift settings.

The cutterhead demands particular attention. Straight knives require regular sharpening or replacement when they become dull. Signs of dull knives include increased effort required to push boards through, burning on the wood surface, or fuzzy rather than smooth cuts. Many woodworkers keep spare sets of knives to minimize downtime when changing becomes necessary.

For those who've upgraded to spiral cutterheads, maintenance becomes much simpler. The carbide inserts last dramatically longer than straight knives and require only rotation when they eventually dull. Each insert has four cutting edges, so you simply loosen the screw, rotate to a fresh edge, and retighten. This process takes minutes compared to the hours required for setting straight knives.

Maintenance schedule:

• Daily: Clear chips, check guard operation

• Weekly: Verify fence squareness, clean tables

• Monthly: Wax tables, check belt tension

• Quarterly: Lubricate adjustment mechanisms, check table alignment

• Annually: Deep clean, check all alignments, replace worn parts

Upgrading Your Jointer with Spiral Cutterheads

The single most impactful upgrade for any jointer is converting from straight knives to a spiral cutterhead. This transformation dramatically improves cut quality, reduces noise, and simplifies maintenance. For those serious about understanding what is a woodworking jointer capable of at its best, spiral cutterheads represent the gold standard.

The benefits become immediately apparent from the first cut. Where straight knives create a chopping action that can tearout difficult grain, spiral heads produce a shearing cut that slices cleanly through even the most challenging woods. The noise reduction alone justifies the upgrade for many woodworkers - spiral heads run significantly quieter, making the shop environment more pleasant and reducing hearing damage risk.

Installation of a Sheartak spiral cutterhead typically requires moderate mechanical skills but transforms an ordinary jointer into a precision instrument. The process involves removing the old cutterhead, installing the new spiral head, and making minor adjustments to table heights. Most woodworkers complete the upgrade in a few hours and immediately notice the improved performance.

The long-term economics also favor spiral heads. While the initial investment is significant, the extended life of carbide inserts compared to straight knives, combined with reduced sharpening costs and downtime, means the upgrade pays for itself over time. Each insert can be rotated four times before replacement, and even then, only the worn inserts need changing rather than entire knife sets.

Jointer Accessories and Enhancements

Beyond the basic machine, several accessories enhance jointer functionality and safety. Understanding what is a jointer used for in woodworking expands when you add these capability-extending accessories.

Magnetic knife-setting jigs revolutionize straight knife installation, ensuring perfect height consistency across all knives. These jigs use powerful magnets to hold knives at the exact height while you tighten the gibs, eliminating the guesswork and frustration of traditional setting methods.

Extended tables either commercial or shop-made, provide crucial support for long boards. Adding even 2 feet of infeed and outfeed support dramatically improves accuracy when jointing boards over 6 feet long. Many woodworkers build permanent outfeed tables at the exact height of their jointer's outfeed table.

Digital angle gauges ensure perfect fence settings for critical operations. While a good square works for 90-degree settings, digital gauges excel when setting specific angles for beveled edges or checking table coplanarity during setup.

Conclusion

Understanding what is a jointer used for in woodworking fundamentally changes how you approach lumber preparation and project quality. This essential machine transforms rough, warped boards into the precise, flat components required for professional-level woodworking. From creating reference surfaces to preparing perfect edges for seamless glue-ups, the jointer proves indispensable for anyone serious about the craft.

The journey from rough lumber to finished furniture begins at the jointer. Master its use, maintain it properly, and consider upgrades like spiral cutterheads to maximize its potential. Whether you're working with a compact 6-inch model or a professional 8-inch machine, the principles remain the same: patient, methodical work at the jointer pays dividends in every subsequent operation.

For those ready to enhance their jointer's performance or explore upgrade options, investigate the premium spiral cutterheads available from Sheartak. The transformation in cut quality, noise reduction, and ease of maintenance will revolutionize your woodworking experience.

Frequently Asked Questions

Q: What is a jointer used for in woodworking that a planer cannot do? A: A jointer creates the initial flat reference surface on warped, twisted, or bowed boards. A planer only makes boards uniformly thick - it cannot remove twist or bow because it references the existing bottom surface. You need the jointer's flat reference surface first, then the planer creates parallel faces.

Q: How do I know what size jointer I need? A: Consider the widest boards you typically work with and add 2 inches for comfort. Most furniture makers find 6-inch jointers adequate, while those building doors or table tops benefit from 8-inch models. Remember that you can joint wider boards by taking multiple passes, though this requires more skill.

Q: What does a jointer do in woodworking that hand planes cannot? A: While hand planes can flatten boards, jointers provide mechanical precision and consistency difficult to achieve by hand. The jointer's machined tables ensure perfect flatness across long boards, and the rotating cutterhead removes material uniformly. Hand planing requires significant skill and time to achieve similar results.

Q: Can I joint end grain on a jointer? A: Never attempt to joint end grain on a standard jointer. The cutting action can cause severe chipout or even dangerous kickback. End grain should be smoothed using a shooting board with a hand plane, disc sander, or specialized end grain routing sleds.