Dovetail Keys as a Timber Joint, ( Part 1)

 

More things to do with do with dovetails.

The project that I’m working on at the moment has twelve timber shelves as part of the design.

I was able to source a selection of recycled messmate and mountain ash in small dressed boards, which I decided to use for this part of the project
The shelves needed to be a 245mm wide and the board’s ranged in width from 40mm to 80mm, so a selection of boards had to be joined together to give me a panel as near to my 245mm width as required for the project.

In an ideal world I’d be able to reach for my domino and hey presto, I’d have the shelves joined; but sadly I don’t have a domino yet, so it’s back to the drawing board.

I have a full router table set up, so another possibility is to use was biscuits, but frankly, I don’t like them You may as well butt-join the pieces for all the additional strength that you’ll gain from them.

After a bit more thought, I settled on butt joining the pieces and then adding dovetail keys, both as a means to prevent the shelves from cupping, as well as a decorative feature.

Another advantage of this method was that I’d used sliding dovetails on the shelves and dividers in the carcasses of the wall unit, so I was very familiar with the required technique.

Once I’d cut all the timber to size and jointed all the edges, the shelves were glued, and butt joined together in lots of three with a couple of sheets of newspaper placed between each of the shelves to prevent them from sticking together. The glued units were then left for 24 hrs to cure.

Once cured the shelves were planed flat to remove any irregularities and sanded to 80 grit.

As there were 12 shelves to add dovetail keys to, I made a simple jig to speed up the process of routing the channels and to ensure continuity of dovetail placement on all the shelves. The jig is just a 3-sided frame, screwed to a sacrificial board with a straight edge attached to guide the router.

The position of the trench is determined by the placement of the straight edge, relative to the edge of the board. Remember to take into account the width of your router base when working out the correct position and double check that everything’s square before you screw the straight edge to the frame.

The next step is to run a straight trench through the shelves to remove the bulk of the excess timber and to minimise strain on the dovetail cutter. I used my Festool of 1010, fitted with a 6 mm spiral uncut but to perform this task.

It’s important not to avoid this step as the removal of the excess material from the trench allows the dovetail bit to perform much better and the bit is under much less strain.

The material I chose for the dovetail keys was 19mm Sydney blue gum that gave an excellent contrast against the messmate in the shelves. So that the keys were balanced in the shelves, I decided to set them in 6mm deep.

The next stage was to set the depth of the spiral cutter in the OF 1010 to 6mm and then cut the square trenches in the shelves.

Remember to check the position of your fence before you start cutting.

If your using two different routers, as I did, the fence will need to be moved into the correct position for the dovetail trenches after you’ve cut the straight trenches.

As in my previous article on sliding dovetails, I again turned to my trusty Bosch Gmr trimmer to cut the dovetail trenches.

With the tool unplugged insert the dovetail cutter into the Gmr and set the depth, so there is 6mm of cutter protruding.

The dovetail cutter depth must be the same as the depth of the straight trench that you cut previously.

Once the trimmer is all set then double check that your fence is in the correct position and cut all of the trenches. Clean up any feathered edges on them and put the shelves aside.

 

 

 

 

Make sure you don’t remove the dovetail cutter from the trimmer or adjust the depth.

The depth of the trench is the same as the height of the dovetail key we’re going to cut in part 2

 

Part 2 of this article will cover how to make the dovetail keys.

As usual, your comments and questions are appreciated

Thanks for reading this article,

Bryan