How to cut out a groove to fit a tongue in a 3D model with the INTERFERE command

By Ellen Finkelstein

Bill Walker sent me the following tip.

Sometimes you need to cut out part of one 3D object to fit another object. For example, in tongue & grove construction, you need to cut out the groove to fit the tongue. You can make this process easy with an option of the INTERFERE command.

Follow these steps:

1. Create an object with a tongue. For example, I drew a closed polyline and extruded it with the EXTRUDE command. (You could also create two boxes and use the UNION command to join them.)

2. Create an object that will receive the tongue. For this example, I’ve made a length of beaded face frame stock. It’s taller than the piece with the tongue, so the associated groove needs to stop at the end of the tongue. Again, you can draw a closed polyline and extrude it.

3. Position the two parts in the orientation that they will take when your model is complete. This is important, because we will be using the actual geometry of the two parts to create their final relationship. You can see that the tongue model interferes with the taller model that will have a groove (to accommodate the tongue).

4.  Switch to a layer whose color contrasts with the colors of the existing objects’ layers.

5. Start the INTERFERE command. At the Select first set of objects or [Nested selection/Settings]: prompt, select both object and press Enter when the prompt repeats.

6. At the Select second set of objects or [Nested selection/checK first set] <checK>: prompt, press Enter to check for interference and open the Interference Checking dialog box.

7.  In the dialog box, make sure to uncheck the  Delete Interference Objects Created on Close check box.  The result is that you create an interference object. You see it here in green.

8. Start the SUBTRACT command. At the Select solids, surfaces, and regions to subtract from .. Select objects: prompt, select the solid that will have the groove and press Enter to end selection. At the Select solids, surfaces, and regions to subtract ..Select objects: prompt, select the interference object you created and press Enter to end selection. You have just created the perfect groove for the tongue.

Here’s the same model and view with the Xray visual style.

Finally, I separated the objects and changed the viewpoint so you can see the groove more clearly.

Thanks to Bill Walker for submitting this tip! He is a 30+ yr. veteran of the Cabinet-Making Business who has focused on 3D modeling in AutoCAD for the last 10 years, ever since he realized that modeling in 3D let him solve problems the same way he would in the shop, but with less mess and noise. He’s a freelance AutoCAD modeler.