Coffee Table / Chest / Play Table (4) – Dados

With the dovetails now cut and dryfit, it is time to create the dado (a groove) in the side panels that will hold the floor of the chest in place.  By planning for the location of the dado to terminate in a tail,  I only have to create stopped dados in the tails, so only on two sides.  The dados on the end pieces can go completely through.  If you don’t plan for it to terminate in a tail, then all 4 dados would  have to be stopped.

I have a nice old dado plane that belonged to my great uncle, and I would have liked to use that for this project, but it is 7/8″ wide … too wide for the thickness of the bottom panel so it would have left too much slop.  So I chose to make my dados with my router, a 1/2″ straight bit and a clamping guide fence.    I’ll take this moment to say that I can’t say enough these clamping guides.  They are easier to use than simply clamping on a long piece of plywood as a fence.  I use them with my router and my circular saw, and they could also do a nice job with a jig saw.

Choice: I have seen lots of nice dado template jigs that make it easy to create exact width dados.  The problem is that they are usually only for stock no wider than 20″ or so.  The long panels are nearly 4′ long so I would have needed to create a template jig just for these two panels and it didn’t seem worth it.

My approach is nearly as simple as using a jig, but gives me a lot more flexibility in terms of the length.   I take a scrap of 1/4″ MDF  ( roughly 18″ long and just wider than the distance from the edge of the router bit to the outside edge of the router base plate).  I then take my clamping guide fence and clamp it near the edge of my workbench.  I place the mdf scrap with a straight edge against the cutting guide and clamp one edge to hold it in place. Then I run the router along the guide fence so that it cuts the MDF scrap to the exact distance from the edge of the router pit to the edge of the router base.  This gives me a setup block that tells me exactly where the router will cut if I place the block against the clamping guide fence.  I actually cut the block in half so now I have two set-up blocks, one for each end of the clamping guide.  I mark on the setup guide which router base and which bit it is for and store them with the router for future use.

First I mark where I need the dado on the panel. I use a piece of scrap of the same thickness as the chest bottom to mark the thickness of the dado (close to 3/4″ in this case).  Then I place the setup block on that mark and now I can position the clamping guide to the panel  so that it just touches the setup block.  It takes a couple of attempts to get it set right, but only a very small amount of time.

Using set-up blocks to set the guide fence.

Using set-up blocks to set the guide fence.

I mark the location of where the dado should stop and then proceed to make one pass with the router.  The dado is only 1/2′ wide at this point – too narrow to hold the bottom.  So now I position the setup block on the other side of dado against the line that marks the thickness I need.  Then I reposition the clamping guide fence and make another pass with the router.  Now the width of the dado matches the thickness of the base.

Routing the stopped dado that terminates in the tails.

Routing the stopped dado that terminates in the tails.

The router bit leaves a rounded corner in the stopped dados so I clean them up with a chisel, being careful not to blow out the ends of the dovetail (that mistake would be visible).

Since there is a cross grain situation with ends of the chest, there will be no glue holding the base in the dado and we want to leave room for some expansion on the width of the base, so the dados on the side panels are cut a bit deeper than they needed to be.  For the width of the base they only needed to be 1/4″ deep, but I made them 3/8″ deep to allow for the bottom panel to expand.  The depth of the dados on the end panels could exactly match what was needed, since the side panels and the base should expand and contract together.

To make it easier to get the bottom panel to settle into the dados on each side, I use a block plane to chamfer the edges of the panel. It won’t affect the strength (remember there is no glue holding the panel) but it will make sure that when clamping the sides all in place for final assembly, that there won’t be any hangups with the bottom panel.

Next up, pattern cutting the “feet” into the panels.

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