LouieAtienza's "Dovetails on the Flat" Technique, take 1

[louieatienza]

OK I think I have found a relatively simple way to achieve dovetails cut on the flat on a 3-axis CNC. Though there are a couple tiny compromises to be made, I think the overall look is more traditional than some of the other techniques previously mentioned, save for vertical mounting or table slotting.

The good? You can nest the drawers relatively easily. You do not need to buy exotic custom bits; all bits I use are stock. This technique produces THROUGH dovetails, where most others (save for slotted tables and vertical clamping) rely on half-blind dovetails. You can make the tails almost as thin as you want; you are not at the mercy of the bit diameter. And the pieces mate almost perfectly, save for a clearance slot that disappears once assembled.

The bad? The cut on the tails is neither square or plumb, though I don't find the look objectionable; in fact it looks distinctive and new. The clearance slot is a necessary flaw that doesn't make for 100% fitment, though it's very close, and the small slots could allow for glue squeezeout. The main possible objection to this technique is that it requires you to a) flip the pieces over and reset once cut, or b) do a quick cut on the tablesaw.

I will break up the steps and explain what's going on, along with pics. I feel however, most of the pics will be self-explanatory.

One caveat I pose is that I used Baltic Birch for this demonstration, forgetting it's actually 12mm. So the end result shows gaps in the joint, equal to the thickness difference from 1/2". D'oh! Anyways, I hope you take this as proof-of-concept...

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[louieatienza]

OK here are the secret weapons: a 30 degree "engraving" bit (need at least 1/2" of cutting length), a 150 degree v-bit (or tablesaw, which is what I used), and your profile bit of choice.

The key to making this work is taking advantage of what may be considered a liability - the "draft" angle produced by the 30 degree cutter. Let's say the drawer side is 1/2" thickness. So 0.5" * sin(15 deg) = 0.129" appoximately. This is the offset from the top to the bottom of the cut as produced by the bit. I'm sure this would work with any angle bit that produces 45 degrees or less of draft, but haven't provevn it yet.

The reason I point this out is that instead of pocketing the waste material (flat area clearing in VCarve Pro), it's faster to do a profile cut, before the v-carving. The drop-offs are so small they won't bind your machine.

Here's what thedrawings of the tails and pins look like:

[louieatienza]

OK to hog out the waste, I simply selected the inverse pins and tails I drew, and inline them 0.130", which left me just enough for cleanup.

Now the clearance slots are needed so that the draft angle is removed from the insides of the tails; otherwise the joint won't fit. This all gets hidden once assembled (it would be on the inside corners)

[louieatienza]

This is what everything should look like to this point:

[louieatienza]

The v-carve paths can now be done. You have to use the original inverse shapes, not the inlined ones!

The tip of the 30 degree v-bit is tiny, so to be safe I did this with 0.125" DOC per pass. To avoid unnecessary macining with the v-bit, I selected "flat clearance with larger bit" and selected a 1/8" endmill. You don't need to use this toolpath, and it can be deleted (the flats are all gone now thanks to the profiling work before). You just want the v-carve path.

[louieatienza]

Here's what everything looks like now:

[louieatienza]

And with the profile path done, and waste material removed. I suggest, if not using a vacuum table, to affix the drawer sides with either a 23 ga. pinner or maybe tabs, before cutting the profile (I just used 1" brads and held them down caveman-style to my spoilboard).

[louieatienza]

Now because of the 15 degree draft angle the v-bit cuts on the bottoms of the pins, it is neccesary to taper the tails to 15 degrees on the INSIDE face.

This can be done easily by aligning all the tails to a straightedge, clamping them down, and using a 150 degree v-bit, OR standing up on the tablesaw. I find the tablesaw method faster; just set the bevel to 15 degrees, and the fence so that the bevel goes right to the edge of the tail bottoms, and rip!

[louieatienza]

Here some assembled views of the joint. Agan, note that there are gaps; this is because I made my designs and measurements based on 1/2" thickness, and mistakenly used Baltic Birch, which is actually 12mm give or take. It wouldn't be too hard to make the necessary adjustments in VCarve Pro.

I also have a pic of the joint opened to reveal the "clearance slot" I made. being on the INSIDE of the box it disappears when assembled. The "reverse" angle on the tails givevs a really cool and I feel new effect. And if you were so unscrupulous, you could make "scribe" lines on everything with the v-bit to further the "handmade" effect!

One note about nesting: It may be helpful to manually nest the drawer sides with the pins facing pins and tails facing tails. Then the invverse profiles could be welded before making toolpaths, which should save a bunch on machine time.

Any comments or suggestion on how to improve this would be helpful. I've gotten a lot of help in this Forum the past couple years and hope this is a cool way to "give back." Also if anyone uses this for a project it would be cool to see the pics here as well!

[louieatienza]

I have the file in VCarve Pro 5.5 as well as CasMate (less the toolpaths) if anyone wants to give this a go!

[CarveOne]

I like it, but I don't think I understand it yet. It looks like it will be a very strong joint when glued.

CarveOne

[louieatienza]

I like it, but I don't think I understand it yet. It looks like it will be a very strong joint when glued.

CarveOne

Hehehe me too! Basically just a variation on a typical through dovetail joint, but with tapered pins and tails. Or imagine cutting the pins and tails with a compound miter...

[michaelthomas]

Our kitchen design software (KCDW) has a nested dovetailed drawer module that out puts to AlphaCam. I build about 20-30 1\2" baltic birch drawers per week. All nested based, and the joints look fairly normal. (Typical 1\2 blind)

Because of the nesting......they always fit like a dream.

[louieatienza]

Our kitchen design software (KCDW) has a nested dovetailed drawer module that out puts to AlphaCam. I build about 20-30 1\2" baltic birch drawers per week. All nested based, and the joints look fairly normal. (Typical 1\2 blind)

Because of the nesting......they always fit like a dream.

While I am aware of the different software packages that contain dovetail drawer modules, to me the cost is prohibitive.

While it's fine for general cabinetry, there are times in woodworking where you WANT the ens of the tails exposed, like in a blanket chest, jewelry box, etc. especially with contrasting woods. Also, a hallmark of hand-cut dovetails is the variation and fineness of the pins. I can make the pins as fine as I want, up to 1/8" at the narrow end.

I don't know of any software package that has a dovetail module that cuts through dovetails on the flat, without need for whittling or adjusting afterwards. I know it can be done on a 5-axis, but I don't have that! Just working out of my basement, with no special software. Heck, I designed this in CasMate 5, which has got to be about 20 years old! Like mentioned earlier, I wouldn't use this for production, but for my one-off stuff, it beats the dovetail saw, scribe, and chisel...

That said, I made a new test piece in MDF, which is closer to 1/2" and the fitment is way better. Still have room to tweak; now my main thing is the .005" tip of the v-bit. My layout didn't take it into account...

[zool]

Absolutely brilliant.

Your geometric conceptualization is astonishing; especially considering that the cause of not perfect on the first cut was the materials.

[louieatienza]

Absolutely brilliant.

Your geometric conceptualization is astonishing; especially considering that the cause of not perfect on the first cut was the materials.

Thanks zool! I hope to experiment more with this method in the coming months. The trick is to use the same angle for the tails as the angle of the v-bit. So a 30 degree cutter would require use of 15 degree tails, and a 45 degree cutter should have 22-1/2 degree tails, and so on.

Theoretically, with a 90 degree bit, one should be able to make a mitered dovetail, which would be REALLY cool! Though I see it in my head, time always makes it tough to put idea to wood!

To note, if one had a router table and a 15 degree dovetail bit, then the PINS could be reverse beveled instead of the TAILS, and may havve a more mechanical advantage. I find however that the tails are easier to trim. However, you would not need to cut the clearance slots, if you were concerned with 100 percent fitment.

I posted some vids of the baltic birch cut in my YouTube channel:

http://www.youtube.com/user/AtienzaL.../1/ocNqwCRo4xE

[RomanLini]

I'm impressed and intrigued by your 3D shaped dovetails Louie. I found this thread through a link in your router thread as I don't normally browse the woodworking forum.

From an engineering point your dovetails will be enormously strong in one direction. Maybe you could cut more complexity so they "lock" something like a wooden puzzle block, to give strength on both directions.

Here's an idea! What about putting some round holes on the side where the 2 pieces can slide apart, so the holes are half in one dovetail on piece1 and half in the dovetail on piece2.

Then putting some small wooden dowels pins in place in the round holes? After that action, it is fully interlocked and cannot slide apart in either direction unless the dowel pins are removed. Just a thought.

[louieatienza]

I'm impressed and intrigued by your 3D shaped dovetails Louie. I found this thread through a link in your router thread as I don't normally browse the woodworking forum.

From an engineering point your dovetails will be enormously strong in one direction. Maybe you could cut more complexity so they "lock" something like a wooden puzzle block, to give strength on both directions.

Here's an idea! What about putting some round holes on the side where the 2 pieces can slide apart, so the holes are half in one dovetail on piece1 and half in the dovetail on piece2.

Then putting some small wooden dowels pins in place in the round holes? After that action, it is fully interlocked and cannot slide apart in either direction unless the dowel pins are removed. Just a thought.

Thanks Roman! Yes there is no mechanical strength is one direction. The tapered tails means precise fitment is crucial. However, there is more joint surface area than on a typical dovetail, which means more glue surface.

There are many ways of adding wooden dowels or pins to lock the joint in the other direction; a favorite of mine is to drill from the top corners after glue-up; your idea is another.

Another option, though a bit mroe difficult, is to make the dovetail in such a way that it slides together in a 45 degree path. This gives it very good mechanical strength in both directions, especially when glued. I propose that with some maneuvering, this cold be done "on the flat" a s well...

In more traditonal cabinetry, the drawers were made to pretty exacting tolerances; in fact, they were made so well that pushing them in caused a "piston" effect, as it was slowed down by a pocket of air. The case sides helped support the drawer sides as well. The stuff was handmade and not cheap, and people took care of their furniture.

Nowadays, most drawers employ drawer slides like Accuride or Blum or similar; and people typically slam their drawers shut. There usually is a 1/2" gap on each side of the drawer, whic to me looks horrid, but is the norm now. Only exception maybe would be the undermont slides. The "soft close" slides have become more popular now/

[Mountaincraft]

Louie..
One of the questions I planned on asking you guys at some point, was if there was a way to do dovetails on the CNC...

Excellent that you developed and posted this... Now if I could just understand how you did it...

You mentioned the files, but I don't see a link for them anywhere.. Did I miss them somehow?

[zool]

Louie..
One of the questions I planned on asking you guys at some point, was if there was a way to do dovetails on the CNC...

Take a look at this and the other suggest youtube pieces: [nomedia="http://www.youtube.com/watch?v=ZGEYO1g6ZcU&feature=related"]YouTube - ‪cutting dovetails on cnc‬‏[/nomedia]