How to Join Wood Planks for a Table Top

Beginning woodworkers tend to stick to projects which can be cut out of solid pieces of wood, whether those are boards of solid wood or plywood products. As they gain experience, they start experimenting with different types of joinery, learning new techniques which allow them to make more complex projects. Success with those encourages more complex joinery, like mortise and tenon joints and even dovetails.

One important step in this process is learning how to join planks together to build tabletops and other large pieces of furniture. Let’s face it, a tabletop made of properly joined together planks looks a whole lot better than one made out of plywood; even hardwood plywood.

But this is a step that gives many woodworkers lots of trepidation. Partially that’s because of the amount of wood that it takes to make a tabletop. Make a mistake gluing it all together and you’re going to be out a lot of money. But if the right steps are followed, the risk of losing money is minimal; and even if a mistake is made, there are ways of rectifying that mistake.

The good news is that it’s not as hard to make a wood plank table as many people think. There are a number of steps that need to be taken and the right tools need to be used; but assuming that the woodworker has the tools and takes care not to miss any step, there’s a very good chance that someone with average woodworking skills can make a beautiful table top on their very first try.

What’s Needed for Making a Wood Plank Table?

One of the things that keeps people from making wood plank table tops is not having all the tools necessary to complete the job. Fortunately, there are alternatives that can be used in some cases. Knowing what those alternatives are gives woodworkers who don’t have as complete a workshop as they’d like the opportunity to make projects of this type.

Bar Clamps

The biggest and most important need for making a plank table is clamps, lots of clamps. These can be parallel bar clamps, pipe clamps, screw clamps or speed clamps. The type doesn’t matter as much as that there are enough of them and the clamps are long enough to span the distance across all the boards being glued together. How many clamps are actually needed will depend a lot on the width of the boards.

The diagram below shows the relative cross sections of different standard size planks. The red lines indicate the pressure lines from clamps, showing how far the pressure from a bar clamp will extend to either side. I drew this diagram to determine the minimum spacing required. That is indicated by the dimensions shown on the bottom. For example, 1”x 4” planks require clamps every 7 inches, while 1”x 8” planks require clamps every 15 inches.

In the case where random width clamp are being used, the spacing can be determined by the plank which is closest to the edge. If that board is a 1”x 6”, then the clamps can be 11” apart, even if the next board is a 1”x 4”. The pressure applied by the clamp will have spread farther out, providing adequate pressure to that second glued joint.

clamp spacing
Clamp spacing

Table Saw 

A table saw is pretty much a have-to for making any plank tabletop, although it is possible to get by without one. The main purpose of the table saw in this project is to establish the width of the boards and make sure that the edges are straight. That can also be done with a jointer. But most woodworkers buy a table saw before a jointer, so it is more likely that they will have a table saw.

Before cutting any boards on a table saw for the tabletop, it’s important to true up the saw. That means verifying that the blade is exactly perpendicular to the table, which can easily be done with a square. It’s also essential to ensure that the fence is exactly parallel to the blade. As the blade is installed perpendicular to the table, all that should have to be done is to make sure that the fence is exactly perpendicular to the edge of the table. Don’t assume it is; it may not have come from the factory set right or may have gotten bumped sometime, causing it to go out of alignment.

The other important thing about the fence is its length. If the table saw is being used to true up a board with a crook in it. That refers to a board that is flat, but the ends of the board move away from the centerline on the same plane as the board. This is often trued-up on a jointer, but if a jointer is not available or the jointer that is available isn’t long enough, then it needs to be trued up on the table saw. To do this, use a long straight edge (a long straight board, piece of MDF or metal) either to extend the fence or attached to the board being trued up. (more on this later)

Jointer

The main purpose of a jointer is to true up the edges of the boards. This means both making sure that the edges of the boards are perpendicular to their face and making sure that there isn’t any of the aforementioned crooks in the boards. Getting rid of those crooks can be difficult with a small jointer and a long board, so a table saw might actually be better for that job. The other option is to add an extension to the outfeed table of the jointer, making it possible to use it for truing up longer boards.

Planer

The planer and the jointer work together. Where the jointer is used to true up the edges of the boards, the planer is used to true up the surface. It is possible to do without this tool, especially if using S4S boards which come from the lumberyard with the surface already smooth.

The other thing that the planer does for us is ensure that all the boards are the same thickness. This is especially important if we are working with rough-sawn boards, but it can be important with S4S lumber purchased from the lumberyard, as there is no guarantee that it is all the same thickness. In fact, it usually isn’t. So it either needs to be run through a planer to establish the thickness, or the assembled tabletop will need to be planed and/or sanded to even up the top.

Hand Plane 

While not an actual requirement, a hand plane can be extremely useful for dealing with tabletops that were made with boards that weren’t run through a planer. This can also be done with a belt sander, but it’s considerably faster to do it with a hand plane.

Cabinet Scraper

Some woodworkers like using a cabinet scraper or card scraper for finish work on their panels. For those who are accustomed to working with one, this is an ideal tool for smoothing out a tabletop, preparing it for finishing. In the hands of a woodworker skilled in its use, a panel scraper can provide a smoother finish than sanding will. Even so, there are many of us who find sanding easier.

Electric Sander

No matter what, the tabletop will need to be sanded, either using a vibratory or random-orbital sander and various grades of sandpaper to smooth it out.

On the first tabletop I built, I didn’t have a planer and wasn’t very good at using a hand plane. So what I ended up doing is using a handheld belt sander to even out the top. I don’t particularly recommend this as a method for use, but if nothing else is available, it works.

Cauls

Cauls are shop-built wood pieces, used to make the glue-up easier. In the case of making a tabletop, cauls are needed which are at least 6” longer than the tabletop is wide. At least two pairs of cauls are needed, as well as clamp to go with each set. For larger tabletops, three or even four sets of cauls is even better.

The idea is to have the bottom cauls run crosswise to the glue-up, setting the boards on the workbench, and then setting the planks to be glued on top of them. Once glued together, the top caul is placed over the bottom one and the two are clamped together. This prevents the possibility of the tabletop bowing when pressure is applied to the main clamps, as well as serving as the primary means of ensuring that the boards are aligned with each other so that one is not higher than the next.

Cauls can be made from 2”x 2” or 2”x 4” material. Try to go with wood that is as knot-free as possible, as the knots will create places in the wood where the pressure is not consistent. Then plane one surface of the caul, giving it a slight curve. For planning, start 3” from the center and take off a shaving all the way to the end. Repeat this every 3”, until the end of the board is reached. Do the same for the other side. Mark the pair of cauls as going together, as upper and lower, and with arrows pointing towards the joining edges. Rub wax all over them to keep glue from sticking.

caul, original board
Caul

Truing Up Planks

The first part of making any tabletop is to true up the planks. This is a bit different for rough-sawn lumber, than it is for S4S board purchased from the lumberyard. However, the real difference is that certain steps don’t have to be done on the S4S lumber, so I’ll describe the process for truing up rough-sawn lumber. When making a tabletop out of S4S boards, simply ignore the first steps.

The very first step in truing up the boards is to either find or create one edge that is straight and true. This is normally done on the jointer. If the jointer’s table is too short for the boards being worked on, an extension can be built for the jointer and attached to the jointer’s fence.

Another option is to use the table saw to do this step. All that’s needed is a long board that’s already trued. A piece ripped off a sheet of plywood or MDF can work for this, as well as a piece of square metal tubing. The idea is to extend the saw’s fence, in order to eliminate any crook in the boards. To do this, either attach the trued piece to the saw’s fence, making it longer, or attach it to the board being trued and use that against the fence to true up the opposite side of the board. Then take it off and flip the board around to true up the opposite side.

The next step is to plane all the boards to the same thickness. This does not necessarily have to be the finished thickness of the tabletop. In fact, it should be about 1/32” to 1/16” thicker, allowing for final planning and sanding.

Lay out the cauls and clamp on the workbench, spreading out the clamps as shown in the chart above. When using multiple clamps in a glue-up, the clamps should be alternated, top and bottom, to ensure that they won’t pull the tabletop into a warp. This risk is reduced when working with cauls, as the cauls fight against that warping, but not totally eliminated.

There is no such chart for cauls, but I would use at least one pair for every two feet of tabletop to help ensure that the boards are perfectly aligned. The cauls can also help to remove minor warping from the boards, but only to a point. It would be good to dry clamp everything together, in order to check whether the cauls can provide enough force to take out the warping, before committing to that action.

Apply a thin layer of glue to one of the adjoining edges of all the boards, setting them together as they are intended to be. Then starting with the clamp for the cauls, tighten up all the clamps in stages, rather than tightening one clamp all the way, before moving on to the next. When the glue starts oozing out of the seams, it’s time to stop applying additional pressure.

Check the glue-up with a straight edge to ensure that the overall panel is not bowing. Allow the tabletop to dry a full 24 hours before removing any of the clamp.

Once the clamps have been removed, chip off the glue beads that squeezed out of the seams with a bench plane, taking care to not scratch the tabletop in the process. Then sand the entire table top with progressively finer grits of sandpaper, starting out with a coarse sandpaper and working through to paper that is at least 220 grit. Due to the large amount of sanding, this is best done with a vibratory sander, like a quarter sheet sander or a “mouse” sander or with a random orbital sander. Of these, the random orbital will take material off more quickly. The tabletop is then ready for any edge profiling, before sanding.

What About Biscuits and Dowels?

There are many people who talk about using biscuits, dowels or dominoes for edge joining boards. While all of these were developed for this express purpose of joining boards together to make tabletops and other large panels, they aren’t actually necessary.

The basic concept behind using any of these methods is that they add strength to the joint. The only problem with that is that a properly glued wood joint, using typical wood glues, is actually stronger than the wood itself. If the tabletop is to break, it won’t be the glue that breaks, but rather the wood fibers on either side of that joint. Adding in these methods of joining merely moves the point of breakage.

Biscuits in particular don’t really help with aligning boards, even though they are supposed to. But because the biscuits are smaller than the slot cut into the edges of the boards and are wider than the thickness of the biscuits, they don’t actually accomplish that. While biscuit joiners were considered “the tool to have” for a number of years, they are waning in popularity, as more and more woodworkers realize that they don’t need to take that extra step.

Dowels and dominoes fit much more snugly than biscuits do. However, the positioning and size of either needs to be exact for them to work, just like a mortise and tenon joint. That shouldn’t surprise anyone, as both of these methods have been developed as a substitute for mortise and tenon joints, when those are needed by woodworkers who do not have the skill or the time for making them. While both are considerably faster than making a mortise and tenon, they still aren’t necessary. As proof of that, there are no examples of old tables where the tabletop has been built using mortise and tenon joints to attach the boards together.

Final Shaping of the Tabletop

When building a tabletop, it’s always a good idea to make the individual planks a bit long. There’s a lot to align when doing the glue-up and it’s all but impossible to get everything aligned perfectly. By making the tabletop an inch or two long, it can be cut to length with a circular saw, after the glue has had a chance to dry.

Care must be taken when crosscutting the ends of the tabletop, as there’s a good chance that the wood may try to splinter. In order to avoid damage to the edges of the table, it’s a good idea to turn the top upside-down, cutting it from the bottom side. That way, any chipping will be hidden.

Of course, this is not a concern if the edges of the tabletop will be routed in any way. Many tables have routed edges, shaping the edges of the boards. Whether this is a simple roundover or a more complicated profile, it will most likely hide any sign of splintering that is left by the saw. Using a freshly sharpened saw blade in the circular saw can also help to reduce any risk of splintering.

But before any edge profile is cut into the tabletop, any necessary shaping will need to be done. Modern plank tables tend to be rectangular, with square ends. But tables haven’t always been made that way. Many antique tables have scalloped edges, often made that way in conjunction with some inlay work. But even in modern styling a round or oval table might be desired, as well as a rectangular table with rounded corner. In any of these cases, the final shape will need to be cut out of a square or rectangular laminate made of planks. It is all but impossible to clamp a round or oval tabletop so that the glue can set.

Making a table with a complex shape, such as the scalloped edge tables commonly found when we look at antique furniture, means cutting the outline with a jigsaw. The risk in doing that is that the jigsaw blade may can’t to one side or the other, especially if sideways pressure is applied to the blade. The combination of heat generated by friction and the sideways pressure can make a blade cant, without the woodworker having any idea of what is happening. Should that happen, then it will be necessary to sand or file the edge of the tabletop to make all edges perfectly vertical, before routing them. Otherwise, the routed profile will end up being uneven.

One alternative to facing this risk is to use a router with a RotoZip bit in it for cutting the outline. In cases where a scalloped design is going to be repeated, it’s a good idea to create a template to be used in conjunction with the RotoZip. Tape the pattern to the woodtop so it doesn’t move, then cut out the outline. Follow that up with routing the edge, sanding and then applying finish to the table.

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