Creating a Pummel, the Square-to-Round Section in Turnings
Often furniture with turned legs and stretchers have pummels or square sections of the turning. Both Dave and I have previously shown methods for handling this complexity. A reader recently asked to see the process again, so here is how I do it using the following model of a 17th C. Connecticut Stool.
Within the turning of each leg there are two square sections (sometimes called pummels) which support the mortise & tenon connections from the rails and skirts. The challenge, both in SketchUp and in actual lathe work, is making the transition from the round portion to the square shape. Sometimes this transition is in an ogee shape, but in this case it is a simple rounded arc transition. See close-up of transition in the following illustration.
Step 1: Create the flat face shape of the turned leg including the square or pummel sections.
Step 2: Turn (in SketchUp use Follow Me Tool) to create the turned sections of the leg.
Note the rectangular shapes of the pummel sections which are still only flat faces.
Step 3: Using the Push/Pull Tool, change the rectangular faces into full 3D pummels.
Step 4: Right click on the front face of the pummel, and select Hide from the pop-up menu. This will allow viewing access into the inside of the pummel.
Step 5: Create a diagonal rectangle from the center of the pummel, then with Arc Tool, draw the transition shape.
Step 6: Use the Move/Copy Tool to move the transition shape away from the leg. Set up for turning this shape with the Follow Me Tool.
Step 7: Execute the Follow Me resulting in the Transition Cutter as shown below.
Step 8: With the Move/Copy Tool, precisely position copies of the transition cutter into the three locations on the leg turning. The middle cutter must be flipped along the blue axis for proper orientation.
At this point I explode any components or groups, select all of the leg including the transition cutters, and scale up the size by a factor of 10 with the Scale Tool.
Step 9: Right click on the selected leg and pick Intersect with Selected from the pop-up menu.
Step 10: Use the Eraser Tool to clean-up waste. Select the entire leg, right click and select Make Component.
Select the leg component and use Scale Tool with factor of 0.10 to bring it back to full size.