How To Cut Lap Joints | Table Sawz
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How To Cut Lap Joints - Lap joints are awesome, and in this guide we show you how to cut yours with your table saw.

How To Cut Lap Joints

Woodworking is a really great hobby and an even better professional. Wood looks nice in the home, it is fun to work with, and the possibilities are endless regarding what you can create.

That being said, there are many different things that you need to know before you start trying to build anything out of wood. One of those things that you need to know about before you start is wood joints, which is how pieces of wood are joined together. Today we are going to teach you everything there is to know about lap joints.

What Is A Half Lap Joint?

A lap joint is a way of quickly joining two pieces of wood together. It is characterized by halving the thickness of both pieces of wood at the joint and then fitting those cut halves together, hence why they are sometimes referred to as half lap joints.

These can then be attached to each other with glue or screws if necessary. Ideally, the joints should be long grain on long grain for the best quality and highest strength. This kind of joint is most often used in cabinetry and when making frames.

There are several different kinds of lap joints including the end lap joint, a corner lap, and a cross lap, a mitered half lap, and dovetail crossed lap, among a few others, some of which are more prevalent than others. Keep in mind, some of these, such as the mitered and dovetail lap are going to be a little stronger, but they are also harder to make. For the purposes of this article we will be focusing on some of the more basic half lap joints.

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What You Will Need To Make A Lap Joint

This is a pretty basic tutorial so you are not going to need a whole lot of material here. There are only a few things required to make a basic lap joint.

  • Table saw
  • Dado blade set
  • 2 pieces of wood (preferable a 1 or 2 x 4)
  • Wood glue

Step By Step – How To Make An End Half Lap Joint

The first kind of half lap joint we are going to help you make is the classic half lap joint, also known as the end half lap joint. This is very easy to and can be done in a few short steps.

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  1. Choosing The Wood – Choose the pieces of wood that you want to use. Ideally, they should be of the same width and height.
  1. Measuring The Depth – On each piece of wood, measure, and mark half way down the depth. This will be the depth of your half lap joint.
  1. Measure The Tongue – On each piece of wood, measure how far you want the length of the half lap to extend into each piece of wood. Remember that this needs to be the same on both pieces.
  1. Adjusting The Dado – On your table saw, expand the dado blade set to be as wide as possible, which is generally around 13/16 of an inch (or install a wide set). This will make it much faster and easier when cutting away the wood to form the half lap.
  1. Height Of The Dado – Raise the dado blade set to the appropriate height. For instance, if you are cutting a half lap joint into a piece of wood 2 inches in height, your dado blade set needs to be raised up 1 inch off of the table.
  1. The Fence – Adjust the fence so that the end of the piece of wood is firmly against it, while the outside edge of the dado blade set does not extend past the length of the half lap joint you are cutting. This will prevent you from cutting too far into the wood along its length.
  1. A Test Run – You should test it out first with 2 scrap pieces of wood which are the same size as the wood you will be using for the finished product. When you have cut the scrap pieces, make sure they fit together so that the faces are flush with one another.

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  1. Making The Cut – Now you can use your table saw, with all settings in place, and the wood already measured and marked, in order to cut the half lap.

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  1. Attaching – You can now use some wood glue along with clamps in order to attach them to each other. If you want you can also follow that up with some screws or pegs for added joint integrity.

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Step By Step – How To Make A Corner Half Lap Joint

The steps for making a corner lap joint are going to be about the same as for the end lap joint, with some minor adjustments. Follow these simple steps to get the job done in no time at all.

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  1. Adjusting The Fence & Dado – Do the same thing with the fence and dado set as in the above example on how to make an end half lap joint. Simply set the fence so that the outside edge of the dado blade set does not protrude past the length of the joint you are looking to make. Also set the blades to the appropriate height, which is going to be half of the height of the pieces of wood in question. You are cutting half way into the wood, so a 3 inch piece will require a cutting depth of 1.5 inches.
  1. Make The Measurements – The important thing to keep in mind here is that it is a corner joint, not an end joint. With an end half lap joint you can technically cut as far into the lengths of the pieces as you want, which is not the case with the corner half lap. The length of the cut in each piece can only be as long as the width of the other piece of wood. For example, if you are using pieces of wood that are 4 inches wide, you need to make the length of the joint in each piece 4 inches. Any longer or shorter and your corner joint is not going to be much of a corner at all.

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  1. Cut, Clamp, & Glue – Make the cut, just as described in the steps for the end lap joint (you can once again use scrap pieces of the same dimensions as your project pieces to make sure that everything will go according to plan). Use clamps and glue to attach them and then follow up with pegs or screws if you require the extra integrity.

Half Lap Joints – Conclusion

When it comes to making half lap joints, they are probably the easiest of all to make. As long as you measure the depth and length of each tongue appropriately, you aren’t going to have any real problems. Also, unless it is an end half lap joint, such as a cross or corner joint, the length of the cut you make (the tongue) cannot be longer than the width of the corresponding piece. As long as you keep that in mind you should be just fine.

 

Sources

https://en.wikipedia.org/wiki/Lap_joint

http://www.woodmagazine.com/woodworking-tips/techniques/joinery/half-lap-joints​

https://www.thespruce.com/basic-joinery-half-lap-joints-3536621​

http://www.woodworkersjournal.com/cutting-lap-joints-with-a-table-saw/​

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