Hand Cut Double Dovetail Experiment

After admiring the double and double-double dovetail joints that are capable with the Incra and other jigs, I started thinking, “Why not try this by hand?” So this box is my first experiment with handcut double dovetails. It took me some time to figure out the joinery process, but once I realized a few things about this type of joint, it seemed do-able. It was quite challenging but also a ton of fun. It also does take some degree of patience and precision…which I’m still working on.

In this blog, I’m focusing on the sides of the box, but here’s a few pictures of the nearly completed box -

Materials.
For this box’s sides I used three types of primary contrasting woods, although there is no real reason to do so. Two contrasting woods would work just as well. The woods I chose are:
 Honduras Rosewood – front and back. Quite hard and brittle. Chopping pins was a slow process with many trips back to “Mr. Tormek” to regrind/hone. But it’s beauty made up for it.
 Caribbean Rosewood – sides. This wood is very close grained, although very hard, it’s not quite as hard as the Honduras variety, and not as brittle. Has some “florescence” when changing the viewing angle.
 Birdseye Maple – inlay (the first dovetails). It’s really pointless to use birdseye in this application, but it’s what I had handy at the time. Regular hard maple would probably work better, maybe even holly.

Construction Keys.
The things I found key when constructing a box like this are:
1) Each side of the box receives a rabbet cut on the inside of each end.
2) The width of the rabbet equals the width of the side to be joined into it.
3) The depth of the rabbet equals the thickness of the initial (or “inlaid”) dovetail – maple in this case.
4) You actually build the box frame (sides) twice, cutting the box apart leaving the first set of dovetails, then cutting dovetails within dovetails.
5) When doing so it’s imperative that all the dovetails use precisely the same angle…all the time. To the degree they are not, the inlaid lines (maple in this case) will not be a consistent width, thus detracting from the overall appearance. You can see some of that in my try here.

The picture below shows the rabbet joint cut on each end of each side –

I set the rabbet depth at 1/8” and cut it on my router table. The decision on the depth of this rabbet made here initially is what “sets” the width of the inlaid dovetail for the entire project. In future boxes using this joinery, I’ll strive to go narrower, (maybe 1/16”) but for the first time this seemed a little risky.

Below is a top-view picture of the pieces in relation to each other once they become integral to the box. In the center is the second of two of my practice joints I tried before starting the box.

The close-up below shows in more detail. From this picture the steps I next took were:
1) cutting tails in the maple (note the sacrificial maple receives no rabbet joint)
2) cutting pins in the Honduras rosewood (the front/back pieces)

The Tails.
Most often I cut my tails first, pins second. The photos series below shows the tail cutting process in the maple -

I don’t normally do this, but for this project I used a small block of wood cut precisely at the dovetail angle for hardwood (1:8) and used this as a “guide block” to rest my saw against for all tails in the box, so they would all be as consistent as possible. This seems like cheating in a way, but it’s critical that both sets of dovetails are all consistent. Again, this is necessary to have an appealing “inlay line” in the maple once I’ve cut the second set of dovetails in the Caribbean rosewood.

These pictures are kind of blurry, but hopefully give the idea –

Below all the saw cuts are made –

Here you can see the relationship of the shoulder in the maple to the rabbet in the rosewood –

In the picture below I’ve made a cut nearly through the waste, but I stop short of going through and finish coming in from the other side. This prevents any chance of the fret saw blade cutting into one of the tails.

Ready for pins –

The Pins.
The next series of photos shows how I mark and cut the pins in the Honduras rosewood. These will accept the maple dovetails. Note again that the maple is sacrificial, meaning it will be cut off once glued into the Honduras rosewood pins –

Below shows how I mark the pins. When I’m doing this for real, my free hand is applying downward pressure on the maple to prevent it from slipping during the marking. The first picture shows squaring everything up prior to marking. Notice that I like to use a light under the pieces when positioning the tails for marking the pins…so that the gap between the maple shoulders and the edge of the rosewood can be easily seen and closed very precisely.

For this project I’m using a x-acto knife. I have marking knives, and I was a little hesitant to try this, but it worked out fine.

Here I’m marking the full thickness of the maple (plus 1/64”) on the rosewood so the pins will be a little proud after glue up –

In this picture I’m cutting out the waste between the pins using a fret saw. Again, at the point of this picture I stop cutting and feed the fret saw down the left side of the waste to finish the cut.

Notice how the pins look in combination with the rabbet initially cut into the rosewood. This is a key to the maple “inlaid” dovetail being visible from the outside of the box sides. Below is a picture of the finished pins -

The next two pictures show trimming the inside edges of the pins/tails. Rob Cosman shows this techique in his video series and this helps remove some of the friction when fitting the joinery -

These shavings are then cut off cleanly using the chisel.

On this project I took this idea one step further and did a small amount of filing on the back of the sides of the pins/tails, to further relieve friction when fitting the joinery together. This photo below is blurry, but I think you can get the idea. Note that I’m angling the file to purposefully avoid having the file come in contact with the front side of the rosewood pin. I also will only do this at the base of the pin…never at the end where it will show once assembled –

The Completed Joint.
If you look closely you can see the pins/tails are slightly proud of the side surfaces –

Even though it’s really hard to “destroy” something I’ve just finished…here I’m cutting the box apart right after getting all the initial corners completed and glued. Notice the remaining maple revealed by the initial rabbet cut into the rosewood –

Below, I’m re-squaring the rosewood to prepare them for the second set of dovetails –

This picture shows the relationship of the Honduras rosewood, to the Caribbean rosewood –

The amount of maple remaining on the inside face of the rosewood is the same thickness that needs to remain in the walls of the maple dovetail, thus determining the size of the Caribbean rosewood tails. Here I’m rechecking this width (after sanding) and will transfer that into the marking of the tails –

Unfortunately this turned out blurry, but this is how I transferred this width to mark the tails in the Caribbean rosewood –

In this picture below you can see how the maple and Caribbean rosewood pins will overlay each other, once cutting and assembly is complete:

This series of pictures show the second set of pins being cut:

At last! The second set of pins/tails are complete!

This picture below shows the groove cut in the sides to accept the base…it also clearly shows my “screw-up” in cutting the groove on both upper and lower sides of one of the sides. My “cover-up” was deciding to place a ¼’ strip of hickory inlay around the inside of the top of the box…whooops! -

This picture shows the hickory base (and inlay) being fitted. The tongue and groove were done on my router table -

Here’s a partial “dry-fit” and I’m ready for glue up. I actually did completely dry fit each corner separately once, but did not do this for all four corners simultaneously, fearing I’d never get them back apart without loosening the joinery fit –

The carcass portion of the box is complete. Here’s a picture of the clamping and end result –

And here’s one after sanding the pins/tails clean… –

I’m currently just starting to apply the finish to this box. The top is 6/4 stock cebil with a contrasting maple stripe that runs across the top, “joining” into the maple in the double dovetail. I’ll post this as a project once I get the finish completed. Thus far I’ve put on one oil coat, but I’m torn between a natural wood look and a multilayered poly/oil blend series of top coats that will end up filling in all grain pores. Any suggestions on the completing finish are welcome.

Even though this blog ended up quite lengthy, I hope you’ve enjoyed it.

-- Martin, Kansas