Boring Holes: Part 2

Tue Nov 12 2024

Note: I did this in May but am only getting around to writing about it now.

The next step in my workbench build is to add some dog holes, which are holes in the bench surface to allow inserting holders against which a work piece can be braced. This again requires boring a large hole through multiple inches of material. My last attempt at this didn’t go so well.

So I started this time by boring some test holes:

Test holes in a scrap piece of wood

Good thing! You’ll notice a lot of tearout at the hole edges in these holes.

Close up of a few test holes showing some rough edges

Turns out the augers in the brace and bit I’m using are quite aggressive and catch the edge of the hole entrance. Using a forstner bit would solve this but it takes forever and the bits aren’t long enough to go all the way through.

I came up with a pretty satisfactory result using the following process. Start by drilling about a half inch down with a forstner bit. Then use some sandpaper to round over the edges of the hole. Once those are smooth, finish the hole using the auger.

Using sandpaper to round over the edges of a hole before fully boring An auger bit aggressively tearing through the wood

I also used an engineer’s square beside the bit to have a reference for square. Kind of wish I had two of these since this only guarantees square in one axis.

An auger bit referenced by a square

I still had a few tear outs. You’ll have to make sure to sand down quite a bit of the edge. In particular with the brace and bit since it tends to move around quite a bit.

After this hole I started producing a larger rounding on the edges and it worked great.

Eyeballing square based on the engineer’s square seemed to have worked well enough. As you can see, some holes are a tiny bit out of square but for dog holes that’s good enough.

Square inserted into the hole shows it's close but slightly out-of-square

All in all, this went much better than the vise holes.

I’ve since added a few more holes on the benchtop as well as on the vise top to allow myself to clamp pieces on top of the benchtop. So far it’s working great!