How to Join Two Boards Lengthwise: A Step-by-Step Guide

How to Join Boards Lengthwise

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Among the most necessary skills that woodworkers should have is the edge joint. As with other things, though, there are multiple ways to get the job done. In fact, there are four primary ways to join boards lengthwise in a secure and efficient manner.

While you won’t need every method for every woodworking job, you should still learn all of them to have the option of using the best one for your situation.

If, at this point, you are wondering how to join boards lengthwise, continue reading. This guide will take you through all four methods in detail.

Edge Joining Boards: The Basics

If you’re entirely new to woodworking, you may not have heard of edge joining just yet. But chances are, you’ve seen it in action. Any time two boards are fastened together flat on their long sides, this is considered an edge joint. This differs from other types of joints, which create right angles or stacks between several boards.

The intended effect of an edge joint is to create a larger, broader piece of lumber that can be used for another purpose in a larger woodworking project. Ideally, an edge joint should also cause its component pieces to align straight and true, thus simulating the effect of a single piece of wood that is as broad as it is long.

4 Ways to Join Two Boards Lengthwise

With the basics out of the way, let’s jump into the how-tos.

#1: Wood Glue

Using wood glue is the first, and in many ways most accessible, method of joining two boards together lengthwise. In essence, it requires you to run a solid bead of wood glue down the length of one board before aligning and affixing the other. After cleaning up the excess glue, this method creates a seamless weld that achieves the desired effect. If you are planning to make a tabletop using this method, make sure to read this detailed guide.

 

Advantages and Disadvantages

Joining Boards Lengthwise with GlueWood gluing has several noteworthy advantages, not least that it is fairly easy to perform. So long as you have two properly sized boards and enough wood glue handy, you can accomplish this kind of joint with ease. For much the same reason, this kind of joint is usually one of the cheapest to form if you lack the specialized tools needed for other joint types.

However, a wood glued joint also tends to be the weakest among the several available options. While modern wood glue is pretty strong, it can hold an excessive amount of weight directly on the joint. Also, due to its tendency to slightly expand when setting, some bowing may occur if the joined boards are not properly clamped together.

Tools and Materials

To complete a successful wood glue edge joint, you’ll need the following:

Step-by-Step Guide

Step 1 – Arrange and Mark the Boards: First, place down your selected boards on a flat workspace. Arrange them as desired so that their wood grains and shades match effectively. Once you’re happy with the aligned boards’ appearance, draw a wide “U” shape with the chalk across the aligned boards. This “U” should open downwards, with outward arching slants traveling down between each board. These marks will make the boards easier to realign after laying down the wood glue.

Step 2 – Apply Wood Glue: Next, stand the bottom-most board in your arrangement on its long end so that the edge you intend to glue is facing up. Then, apply a continuous bead of wood glue down the entire length of this edge. This bead should only be 3/16-inch wide at most so as to prevent excess from spilling out. Remember that leftover glue residue will be more challenging to finish later on.

Step 3 – Slide Together and Clamp: Following your chalk guides, slide your wood boards back together. Once the boards are properly aligned, apply pressure using your clamps. This ensures that the glue is spread out and sets evenly across the entire joint. Wait around 20 minutes, then move on to the final step.

Step 4 – Remove Excess Glue: As you brought your glued planks together, you likely noticed some glue spilling out. This is okay, as long as you remove it before it dries. This may occur after 20 minutes or so of setting. So, once the excess glue is solidified yet still mailable, sheer it off using a wood chisel. This ensures that your glued joint is almost invisible and as tidy as can be.

#2: Biscuit Joiner

A biscuit joiner is a less popular joining method, not least because it requires some specialized tools and materials. To be specific, this method requires the creation of several long, thin channels in each piece of wood. A thin, football-shaped joiner piece known as a “biscuit” is then inserted into the channels, creating tension between the two boards and ensuring they remain together.

Using Biscuits to Join Boards Lengthwise

Advantages and Disadvantages

As noted, many woodworkers avoid using biscuit joints for this purpose because they require specialized tools and materials (namely, the biscuits). Moreover, biscuit joints are not great at maintaining lateral pressure, which increases the risk for bowing if the joined panel is used to bear weight.

However, a new biscuit joint can be ideal in some limited situations. For example, they are ideal for joining sheet goods due to their size and broad tension point. Also, a biscuit joint can help support already-bowed-out boards with ease.

Tools and Materials

To complete a successful biscuit joint, you’ll need the following:

  • Two pre-selected boards
  • Correctly-sized biscuits
  • A biscuit joiner (see my favorite one on Amazon)
  • Pencil
  • Ruler or tape measure
  • Spray bottle with water
  • Clamp

Step-by-Step Guide

Step 1 – Align Boards and Mark Slots: First, you should align each of your boards as desired. This should take into account their colors and grain to ensure a seamless appearance. Once you’ve done so, mark out three or more points across the length of the joined edges for the biscuits’ locations. These points should be equidistant from one another. Then, separate the two boards and mark the actual slot locations. These slots should be centered on your previous mark and should be as long as the biscuit you intend to use.

Step 2 – Set Joiner and Make Cuts: Once you know where you need to cut, get out your biscuit joiner and adjust its settings as needed. Ideally, your slots should be half as deep as your chosen biscuits are wide. Once you’ve adjusted the plunge depth and centered the device, you can begin to make each cut.

Step 3 – Insert Biscuits, Apply Water, and Set: After clearing excessing dust out of the cuts, you can insert your biscuits into one of the slot sets (usually the bottom-most board in the arrangement). Once they are properly set into the slots, spray each biscuit with water to activate any clue or sealant inside it. Then, slide the board with the biscuits into the other slotted board. Clamp the entire panel and allow the biscuits to set for several hours before applying other pressure.

#3: Kreg Jig

Using pocket holes is a method you may have seen used professionally for in-home furniture such as tables and desks. In essence, this kind of joint uses a Kreg jig or other similar tool and creates an angled pocket hole into which a pocket hole screw is inserted. This screw’s insertion angle then allows it to hold the joint together while maintaining flush outer surface on the panel.

Joining Boards Lengthwise with Kreg Jig

Advantages and Disadvantages

Kreg jigs come with various advantages, not least that they are super sturdy. This is a result of the angle at which they are affixed, not to mention the use of a metal fastener (that is to say, metal screws). They’re also fairly easy to create, so long as you have the proper pocket-hole creation tool.

That actually leads to one of this method’s disadvantages – the need for a specialized tool. Pocket hole makers don’t get much use outside this method, so some may be reluctant to spend money on something they rarely use. Kreg jigs do take some practice to perfect though, and can only be used in tough, sturdy wood planks due to the lateral pressure created when drilling the pocket-hole.

Tools and Materials

To complete a Kreg jig edge joint, you’ll need the following:

Step-by-Step Guide

Step 1 – Measure Planks and Set Depth Collar: First, you’ll need to measure the width of your plank. Then, use this measurement to adjust the depth collar on your drill bit. This will ensure that your pocket hole is only as deep as necessary. Many units have a useful measurement chart for this purpose attached to the Kreg jig’s base. After making this adjustment, be sure to raise the correct guide hole upon the positioning of your pocket-holes.

Step 2 – Clamp in Wood and Begin Drilling: After making all the necessary adjustments, clamp in your piece of lumber. Be sure to line up the lumber with your chosen guide holes at this point. Once you’ve done this, you can insert your drill bit into the guide hole and begin drilling. You should always make at least two or three sets of pocket holes to ensure maximum stability of your joint.

Step 3 – Finish Joint: Once you finish drilling, grab the other plank that will be affixed to the one you just drilled. Align them as necessary, clamp them, and then grab your screws. Using your drilling, insert these screws into the pocket-hole until they pierce into the other wood plank. Continue drilling until the screw head is flush inside the pocket-hole.

#4: Dowels

As this technique’s name suggests, this method makes use of cut dowels to act as a tension point between two boards. This kind of joint is fairly sturdy and very flexible in its use.

Advantages and Disadvantages

One of the major advantages of this technique is its use of common woodworking tools.

In fact, so long as you purchase and cut your dowel rods in advance, this can also be one of the quickest kinds of joints to create. However, this technique does require very precise measurements. As such, those who wish to use it should practice on scrap wood before making any final cuts.

Tools and Materials

To complete a dowel joint, you’ll need the following:

  • Two pre-selected boards
  • Pre-cut dowels (see my favorite set on Amazon)
  • Masking tape
  • Pencil
  • Ruler
  • Depth gauge
  • Mallet
  • Clamp
  • Adhesive (optional)
  • Cordless drill
  • Boring drill bits

Step-by-Step Guide

Step 1 – Measure Out Dowel Locations: First, you’ll need to measure out your dowel locations. To do this, use your ruler, depth gauge, and pencil to mark a series of equidistant points. Be sure that these points account for the width of your boards as well as the size of your dowels. Also, be sure to double- and triple-check these measurements. Even minor differences can lead to an uneven panel finish.

Step 2 – Drill First Hole and Test: Pick out a drill bit that is of the correct diameter for your chosen dowel rods. Add a strip of masking tape around that bit at a depth equal to half of your dowel’s full length. Then, attach the bit to the drill and make your first test hole. After removing any sawdust, test to ensure that your dowel fits. This fit should be plenty snug, so don’t be afraid to pound it in with a mallet.

Step 3 – Drill Remaining Holes and Insert Dowels: Once you’ve gotten the hole diameter and depth just right, bore out the other remaining holes. Then, insert the remaining dowel rods and ensure they are snuggly secure.

Step 4 – Clamp and Set: If you are using a glue or adhesive, apply it now onto the dowels. Then, connect your two lumber pieces by sliding the piece without dowels onto the piece with dowels via the drilled holes. This may also require extra pressure from your mallet. Once connected, mount the unified panel into your clamps and allow it to set for several hours.

What Is the Best Method for Joining Long Boards Lengthwise?

In most cases, you’ll find that dowel joints and Kreg jig joints will provide you with the most durability and versatility for your money.

These can be used for a wide variety of jobs and can often be customized to fit your needs. However, if you’re looking for a quick joint between two long boards, wood glue will do the job fine. This is especially true for ornamental attachments to a cabinet, chest, or dresser.

Summary

As you can see, you have a variety of options when it comes to joining boards lengthwise. Any of these edge joining methods could help enhance your next woodworking project, so long as you take their advantages and disadvantages into account. Don’t forget to practice each type of edge joint on some scrap wood as well.

After all, practice makes perfect when it comes to making flat edge joints or improving any of your other practical woodworking skills.

If you are interested in wood joinery in general and want to know more about dovetail joint, butt joint, dado, and other techniques, make sure to also check this article.