Dadoes: Tips & Tricks
By: Chelsea Rodgers
When it comes to joinery in woodworking, dadoes can be a little confusing, and often mistaken to be the same thing. A dado is simply a rectangular groove that is cut across the grain of a board. The joint formed by placing an intersecting board into that groove.
The dado joint allows the load on the board to rest along the full length of the dado, thereby giving it considerable load-bearing capacity. Because the end of the board is entirely encased by the dado's sides, the board can not cup or tilt. The dado joint does not offer any protection against the shelf pulling out of the side unless glued or fastened in some manner, and because the joint involves end grain, the gluing strength is limited.
Dadoes are generally made with a dado set that you attach to a table saw, but we’re going to tell you other ways you can make dadoes, aside from the table saw.
Dadoes and The Miter Saw
Not everyone knows this, but you can make dadoes on your miter saw. Yes, on your miter saw. No need to put a dado head on your table saw, or set up a router bit in a hand-held router or on a router table. If your miter saw has the right flip down stop, you can use it to make dadoes.
HOW IT WORKS
If your miter saw has a flip down stop, you can use it to limit how far the blade will penetrate into your material. The combination of the flip stop and, on most saws, a bolt, lets you dial in depth of cut pretty accurately. Of course when the flip stop is out of the way, you can cut full depth.
CUTTING FULL WIDTH
When you use the flip stop to limit depth of cut you’ll find that the kerfs or dadoes you cut don’t call all the way to the edge of the board that’s against the fence. This isn’t a big deal, and is easy to overcome. Simply place a spacer against the fence so the board you’re cutting is pushed forward; off the fence. It’ll take a little experimentation to figure out how wide the sacrificial board should be, but a board about 1-½” wide should do it.
The best blade for these cuts would be an FTG; flat top grind. That’ll leave you with a nice flat bottom on the dado. If you don’t have that particular blade, don’t sweat it. You can still make dadoes. You just won’t get a dead flat bottom.
DADOES WITH A SINGLE BLADE
Sure, it’s great to cut dadoes using a dado head on a table saw, or a router bit on a router table or with a hand-held router. But there are instances where that may not work for you. Maybe you don’t own a dado head, or the right size router bit. Or maybe you’re only making one dado and don’t want to bother setting up those tools. Here’s another solution for cutting dadoes; you can use a single blade on your table saw, and make multiple passes. The good news, you don’t have to set up a dado head or router. However, there’s a however.
What makes single blade dadoes tough is setting up to produce dadoes that are the perfect width. Good dado joinery comes from having a good fit between the dado and the mating piece, so it’s important to get the fit right.
The best blade for this operation is an FTG-Flat Top Grind. This type of tooth geometry will leave the dadoes with a perfectly flat bottom. Other tooth types, like alternate top bevel, will leave ridges in the bottom of the dado and adversely affect glue strength.
HAND-HELD ROUTER/ROUTER TABLE
With a router edge guide in place, or the OnPoint Laser Guided Router Plate (MLCS item #9098), your hand-held router becomes the perfect tool for cutting dadoes. With your router edge guide in place, you’ll make a preliminary pass and measure the width of the cut with calipers.
Then measure the thickness of the piece that will fit into the dado. Take the width of your insert piece and subtract the width of the dado. The difference is the adjustment you need for the second pass. After you’ve dialed in the adjustment, you’ll make the second pass which will be the exact width needed for precision-fit joinery.
OnPoint Laser Guided Router Plate (MLCS item
When using a Router Tabletop and Fence (MLCS item #9624), the table fence becomes your edge guide. You use the same adjustments as you would with an edge guide. Keep in mind, when using a router table the work is inverted can be helpful to make starting and stopping points on the table as needed.
Router Table and Fence (MLCS item # 9624)