How do I add a fillet with an exact radius in the 3D view, and why did removing a fillet change my shape?

What changed in 12.5

The Create Fillets tool now works in the 3D view. There it shows a live preview of the fillet before you click, and lets you type the radius at the cursor. In the 2D view the tool works as before, driven by the form.

Steps (3D view)

1. Open Create Fillets from the Drawing tab.
2. Choose the Fillet Type and enter a starting Radius.
3. Hover over a corner. The cursor shows a check mark when the corner can be filleted, and a preview of the fillet appears.
4. To change the radius for this corner, type a new value while hovering and press Enter.
5. Click to create the fillet.

Which fillet type

• Normal Fillet: a plain rounded corner. Use it for design, not for making slots fit.
• Dog-Bone Fillet: a circular relief placed so the circle touches the original sharp corner. The documentation says not to use it when the slot width and the tool are similar in size.
• T-Bone Fillet: a circular relief that grows out to one side. Use it when the slot width and tool are similar in size. Clicking right on the corner puts it on the longest side. Clicking just to one side of the corner chooses that side.

Removing a fillet, and the gotcha

Hover over an existing fillet. If it can be removed the cursor shows a cross. Click to remove it.

The software does not remember what the corner looked like before. It always rebuilds the corner by extending two straight lines until they meet. If the fillet was made across arcs, Bezier curves or several spans, the result is a sharp straight-line corner, not your original curve. When that matters, use Undo (Ctrl+Z) right away instead of the remove click, or keep a copy of the original vector on a hidden layer.

Pro tips

• Set the radius for dog-bone and T-bone reliefs from the radius of the bit that will cut the slot, and test the fit on scrap before cutting a full set of joints.
• Trim and extend also work in the 3D view in 12.5, so a corner can be cleaned up and filleted without leaving that view.
• See the entry on the Dogbone gadget for adding reliefs to many corners at once, and the entry on dog-bone or T-bone fillets for where to place them on joints.