Case Joints in SketchUp – Easy in 2017 Pro

How far do you go with details in a SketchUp model? That’s a common question and the answer depends on what you’re making the model for versus how much time it will take to add the details. In my work, I tend to add all the details for all the joinery. That adds a tremendous value to the model when I get to the shop; in a complex case like the one at right I will have a reference to the size and location of every mortise, every tenon, all the tongues and all the grooves. This is a piece from the early 1900s and the guy who built the original had to do a lot of head scratching and calculating at the bench.

With an accurate model the hours that would have been spent figuring out what goes where can be spent doing actual work. In my work flow I first put all the pieces in place before detailing the joinery. I can work on copies of pieces out in space (because I make every part a component). That lets me add the joinery without disturbing the arrangement of the assembled parts.

In this example I copied the horizontal parts on the face of this cabinet out in empty space and added the tenons. In SketchUp, it’s possible to use the tenons to make the mortises. One way to tell how much of a nerd you are is to examine the things you get excited about. When SketchUp 8 was released, solid tools were added to SketchUp Pro. The solid tools make it possible to use a tenon in one part to cut a mortise in another. This is possible in SketchUp Make, but it takes a few extra steps. If you have a complex piece with lots of joints, every click of the mouse takes time. If you can save time modeling you get to shop sooner. The release of SketchUp 8 got me excited and the release of SketchUp 2017 made me positively giddy.

This post details how to make a mortise from a tenon with the free version of SketchUp, SketchUp Make.

The Trim tool speeds up the process. With the Trim tool, SketchUp examines the geometry in one component and adds new geometry to another component to make room for it. If the parts are in the correct position when this is done, the joints will be where they belong in both parts. In this particular case, as in a lot of Arts & Crafts period furniture, there are small offsets in the faces of parts. The rails are a bit behind the legs, the panels are a bit behind the rails, and so on. It’s a great look, but a pain to remember in the shop. With SketchUp I can print a detail of each part to lay out the joinery exactly where it belongs.

The way the trim tool works is you “use this to cut that”. In the image above there is an extra leg component in the foreground to help show how this works. Get the trim tool from the toolbar, click on the component that has the tenon then click on the adjacent part to create the mortise.

As awesome as this feature is, there is a catch to it. When the Trim tool is finished, the original component is transformed into a group. This means that the mortise we just made won’t appear in the other instances of that component still in position in the model. We need to turn the newly created group back into the good old component. That can be done with a few right clicks; explode the group and while all the geometry is still selected, right-click again and make it a component with the exact same name. That puts the new geometry into all the components in the model.

This post details how to do this in earlier versions of SketchUp.

In SketchUp 2017, you no longer need to explode the group and redefine it as the original component. All you need to do is right-click over the group and select “Make Component” from the context menu.

The “Create Component” window appears, but the definition is the same as it was before the Trim tool turned it into a group. Click “Create” and a window appears to warn you that there is already a component with that name in the model. That’s a good thing for when you click “Yes” all the components still in the model will change to include the new geometry.

That saves a couple of steps, the most important of which is you don’t need to retype the component’s definition name. In the old versions of using this trick, typing the exact same name was critical. If you didn’t remember that the name was “front leg” instead of “leg front” the parts within the model wouldn’t change.

This isn’t that big a deal if you only have a couple of joints to make, but it becomes huge when the model has the complexity of this one. All those steps and clicks add up. It still took a while to add all the joinery, but nowhere near the time it would take to add each joint manually.

If you use SketchUp for woodworking, you need to get a copy of my book the “New Woodworker’s Guide to SketchUp”. It’s full of techniques like this that make your modeling more efficient, more accurate and more fun. You’ll be out in the shop building for real in less time and you’ll be armed with accurate information that makes your shop time more efficient, more accurate and more fun.

Bob Lang



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