How big of a gap can you fill with wood filler?
However, it does have its limits with how much it can cover. Anything more than 3/8-inch isn’t advisable. Aside from that, you can sand, paint, and wood stain putty after it hardens.
Can you fill large holes with wood filler?
All it involves is applying a thick layer of wood glue to the hole, filling it with sawdust, and then sealing it with a thick layer of wood glue overtop. If you are really worried about the hole opening back up, you could even mix sawdust with a large quantity of wood glue to make your own home-made wood filler paste.
