Make a Mortise from a Tenon with SketchUp

Mortises_CopyRedefineHere is one of my favorite moves in SketchUp, exploding and redefining components to move geometry from one component to another. If you don’t speak SketchUp fluently, that means I can take an existing tenon from a table apron and use that to make a perfect mortise in the leg. It only takes a couple of minutes, and this video shows you how. The video is one of the ones that are embedded in the text of my book “Woodworker’s Guide to SketchUp”. Following the video is the text related to the video, adapted from the book.

You can build from a SketchUp model without adding joinery details, but if you do, you will miss another of the advantages of planning your work in SketchUp. If you take a few minutes to add the mortises and tenons, you can head to the shop with a detailed, dimensioned drawing that will show you where both parts of the joints are located. You won’t have to calculate the locations of mortises from the tenons and remember about the offset between the aprons and the legs.

By making copies and editing components, the mortises can be located exactly where they need to be in the legs quickly and painlessly. Copy one leg, and one of each of the aprons off to the side of the rest of the model. What we are about to do risks changing the orientation of all the legs, so we want to select the original leg.
If you don’t remember which leg that was, drag a new one into the modelling space from the Components window and compare the sides of the legs that are tapered. The copy from the Components window is oriented in the same way as the original. When you don’t need it any longer, you can delete it. Deleting an instance of a Component only removes that one. The rest of them in the model are still there, as is the version in the Components window.
Select all three components that were just copied, right click and pick Explode from the menu. There won’t be any loud noises and you won’t have to wait for any dust to settle, but the leg and both aprons will now be a bunch of edges and faces. The Explode command only affects the individual components selected. The other components in the model, and the copy in the components window remain.
Erase all parts of the aprons except for the tenons embedded in the leg. Orbit and Zoom so you have a close view of the inside of the leg. You should be able to see the end of the tenon and the face that was the end of the apron surrounding it. Use the select arrow and pick the small faces that were the ends of the tenons and erase them with the Delete key. Erase any other extra lines.
This looks like the leg we want, but it isn’t a component any longer. It is just a lot of edges and faces. We can select all the geometry and make it a Component again, but the real trick is how we name it. If we give it the exact name that we used before, the other Components in the model with that name will update to reflect the differences between the old Component named “leg” and the new one. If however, we give it a name that is different, we make a new Component, and the instances in the model won’t change. Check the name of the component by looking at the list in the Components window. One of the advantages of working with Components is they are expendable. It doesn’t cost anything to sacrifice a Component for geometry we need to use someplace else. There is an unlimited supply waiting in the Components window.

Stuff like this is one of the reasons “Woodworker’s Guide to SketchUp” is one of the most valuable tools you can own. It teaches you great techniques that make you a better SketchUp modeler, and a better woodworker.


–Bob Lang

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