Small Butterfly Dovetails

[alex grams]

I am trying to make some butterfly dovetails for a project that are roughly about 2" long and 1/2" wide at the end of the tails. The problem I am having is making them precise enough, given that a butterfly dovetail seems to be about half as forgiving as a normal dovetail.

I post this on neander, because i figure someone here would know better how to do it, though I am not abject to using power tools to achieve what I want. Though the problem I am having with the idea of machining them is that the pieces are small enough that I don't feel it is safe to work with them.

My first approach was to route the female pattern of the tails into the wood, then cut the dovetails to fit that, that way the wood will have symmetric identical dovetails cut into them. But what I am finding is that the fitting and size of the dovetail into the cut is very very finicky, to have the proper width of dovetail and length, I either get an unacceptable gap at the end of the tail, or the tails aren't wide enough and dont pull the pieces together sufficiently.

My second thought is to cut the butterfly dovetail inserts, then line them up on the two pieces, mark, and hand cut. I Think this may be the best way, but will require some practice.

Ideas? Thoughts?

[Johnny Kleso]

I thinking if you route a female then a sample through in some wood or plastic and lay it over the female..
Flip it end for end and see if your template is a perfect at either end..

Also are you using a 1/8"router bit?
If not try using a smaller or bigger bit to rough out first or try adding some tamp around the guide bushing before finish cut..

Check you your gude bushing for concentricty..

[Sean Hughto]

It's not that hard. Use a handsaw to cut out the bowties. shave them with a chisel if necessary to pretty them up - or correct any lack of squareness to the faces along the narrow edges.

Place teh bowtie where you want it. Mark with a sharp marking knife. Use a chisel and the marking knife to excavate the recess taking specail care to maintain the edges. Stop when you've removed enough to leave teh bowtie slightly proud.

Glue it in. Rubber mallet and or clamp to drive home and let set. Remove the proudness with a chisel, flush cut saw, sandpaper, etc. as you see fit.

[James Scheffler]

...or the tails aren't wide enough and dont pull the pieces together sufficiently.

My second thought is to cut the butterfly dovetail inserts, then line them up on the two pieces, mark, and hand cut. I Think this may be the best way, but will require some practice.

Ideas? Thoughts?

Are you relying on the tails to pull the joint closed? If so, you need to pull the joint closed (clamp if necessary) and then lay out your dovetails. Your "second though" is the way to go. Make the tail insert first and then use it to mark the cuts on the board that you will need.

You might be able to rough out those cuts on the bandsaw, if you have one, going up as close to the mark as you dare. That way, your cuts will at least be square to the face of the board. Then just pare an equal amount with a chisel until the insert fits.

Jim

[Dale Osowski]

This may be different from what you are doing but it may help. The butterflies were cut first using a coping saw and dozuki. After I refined the shape I then outlined the shape onto the material to be cut away. I roughed away material with small trim router and cleaned to the lines with chisel and files.

I have done the same with dovetailed drawers where the tails are the shape of one half the butterfly. It's still a similar process to standard dovetails.http://i65.photobucket.com/albums/h235/Timberwerks/IMG_1795-1.jpg

[Brian Ashton]

I am trying to make some butterfly dovetails for a project that are roughly about 2" long and 1/2" wide at the end of the tails. The problem I am having is making them precise enough, given that a butterfly dovetail seems to be about half as forgiving as a normal dovetail.

I post this on neander, because i figure someone here would know better how to do it, though I am not abject to using power tools to achieve what I want. Though the problem I am having with the idea of machining them is that the pieces are small enough that I don't feel it is safe to work with them.

My first approach was to route the female pattern of the tails into the wood, then cut the dovetails to fit that, that way the wood will have symmetric identical dovetails cut into them. But what I am finding is that the fitting and size of the dovetail into the cut is very very finicky, to have the proper width of dovetail and length, I either get an unacceptable gap at the end of the tail, or the tails aren't wide enough and dont pull the pieces together sufficiently.

My second thought is to cut the butterfly dovetail inserts, then line them up on the two pieces, mark, and hand cut. I Think this may be the best way, but will require some practice.

Ideas? Thoughts?

I've put in a few butterflies over the years. A few things will help you:

I make the butterfly first. I prefer to make them on the table saw so I get real straight edges. Don't make the butterfly shape to complex otherwise transferring it's shape to the piece will be difficult to fit to.

I like to use a wood for the butterflies that is much harder then the piece, like cocobolo or ebony.

Because it can be difficult to fit butterflies precisely I like to tapper them ever so slightly so when then get tapped in they tighten up nicely by crushing the fibres in the high spots (or low spots depending how you look at it) of the piece. I've found this makes it relatively easy to fit butterflies to complex shapes such as turning.

[Frank Drew]

I'd do it as Sean and others have outlined, by making the inserts first, clean them up as best you can, and then scribing their shapes where they'll go on the work. You don't have to make them one by one, though; cut the shape into a wider, crossgrain piece of wood as accurately as you can, then rip off individual pieces in the desired thickness.

I'd probably route the bottom of the recess, either with a hand or electric router, keeping away from the sides so you don't mess up the final fit.

[alex grams]

Thanks for all the input. Part of the challenge is going to be that the wood I am putting the dovetails into is 2" deep. So it is either make a dovetail for each face about 1/2" deep, or a single dovetail full width of the board. I think i would be best to make single dovetails that only go about 1/2" deep, not full depth, that way I can mark and cut the dovetails individually on each side.

Now the problem is that I am going to have 2 dovetails on each side of each let, with 4 legs per table and two tables... so 32 dovetails to cut up.... some good practice on dovetail cutting I guess. I will make a plung router guide so I can do the bulk of material removal with the router, then trim up the insides with chisels.

I think I will put the legs together (i can glue the joints, then clamp them together or hide a screw on the bottom side to hold them) then mark and cut the dovetails while the legs are secured together, and then put the dovetails in. This way the dovetails can give strength to the joint, and I am assured the joint is tight.

Now to set up a few jigs and do some practice cutting!

[Frank Drew]

So it is either make a dovetail for each face about 1/2" deep, or a single dovetail full width of the board.

Alex,

I would absolutely, positively not do through butterfly plugs in 2" material; even 1/2" is deeper than most people inlay these patches in smallish work, in my experience. I'd think that 1/8" to 1/4" is more the norm.


I think I will put the legs together (i can glue the joints, then clamp them together or hide a screw on the bottom side to hold them)
What kind of joint do you plan to use? Mortise and tenon? Whatever, I'd wait until the glue is cured to begin cutting your recesses.

[alex grams]

Frank,
The joint on the legs will be a flat butt. I am looking at the dovetails to be a majority of the strength of the joint, giving me some face to face gluing surface, as the butt joint between the two pieces themselves are end grain to face grain. I intend to have some joint strength from the dovetails, not have them be purely aesthetic. The phrasing of your question seems to imply you think the dovetails are purely aesthetic.

Do you see a problem with the dovetails serving as a strengthening function of the joint?

Or do you see no gain in the joint from going from 1/4" to 1/2" deep butterflies?

The glueing/screwing of the joint before hand would be to pull the two pieces tightly together prior to inserting the dovetail, and i would of course let it fully cure before starting in on putting in the dovetails.

[Frank Drew]

Alex,

I like mortise and tenon joints for this kind of application, but that's not to say that four 1/2" inlaid butterflies per joint, as you propose, wouldn't be adequate.

Be careful, though, when cutting your recesses not to pop the joints loose; even reinforced with a screw at the bottom, there won't be much strength in a butted glue joint, as you've noted.

[alex grams]

I may do a floating tenon also then, to assure the joint is tight before I start cutting my dovetails.

Thanks for the input. My first shot at butterfly dovetails.

[Prashun Patel]

You're really making a spline joint, which can be strong, but probably not as strong as a real tenon.

If it were me, I'd use floating/dowel/M&T joinery for the joints.

Then I'd use a $30 router inlay kit which will give you the template, the bushing and the bit to cut these perfectly and quickly and consistently. The only handcleanup you'll have to do is in the corners of the recesses. I'd make the inlays only about 1/4" thick. In fact, since you'd be doing this purely for aesthetics, you might consider making only 1 per joint...

[alex grams]

Shawn, I am not sure of the semantics of a spline vs floating tenon, from my experience a spline is visible on the ends, whereas a floating tenon is not.

I expect to receive some strength from the dovetails, they are not purely for aesthetics.

I think the tenon/spline would be overkill anyways, as the joint is not a load bearing joint. The majority of force in the joint will be vertically through one leg and not transferred to the secondary horizontal piece. the intent of the tenon is to tighten the joint prior to cutting the dovetail insert.

I have the router inlay kit with bushings for cutting inlays, but call me crazy, I would like to have the dovetails hand cut instead of machined. I will make some jigs for roughing out the bulk of the material, but want to hand cut/chisel the joints flush.

[Sean Hughto]

I think mortise and tenons would be the better joint for strength here. The dt elements could be more decorative, and then need be only inlay thickness (less than 1/8th).

[Prashun Patel]

I have the router inlay kit with bushings for cutting inlays, but call me crazy, I would like to have the dovetails hand cut instead of machined.

Gotcha! You just mentioned initially that you were not averse to power tools.

[Louie Ballis]

You're really making a spline joint, which can be strong, but probably not as strong as a real tenon.

If it were me, I'd use floating/dowel/M&T joinery for the joints.

Then I'd use a $30 router inlay kit which will give you the template, the bushing and the bit to cut these perfectly and quickly and consistently. The only handcleanup you'll have to do is in the corners of the recesses. I'd make the inlays only about 1/4" thick. In fact, since you'd be doing this purely for aesthetics, you might consider making only 1 per joint...


+1 on this. Esp. the template. That will give you uniform dovetails and look grreat with contrasting color wood.

If you dont want to M/T could you use a biscut?

[Brent Ring]

You're really making a spline joint, which can be strong, but probably not as strong as a real tenon.

If it were me, I'd use floating/dowel/M&T joinery for the joints.

Then I'd use a $30 router inlay kit which will give you the template, the bushing and the bit to cut these perfectly and quickly and consistently. The only handcleanup you'll have to do is in the corners of the recesses. I'd make the inlays only about 1/4" thick. In fact, since you'd be doing this purely for aesthetics, you might consider making only 1 per joint...

Shawn nailed it here - Floating tenons would offer the best joint strength.

Very cool design !

[alex grams]

Shawn, i am not averse to using power tools, but that all depends on how good of a job I can do by hand:confused:

Thanks for the ton of feedback, I feel like I have made a mountain out of a molehill. I am going to go the route of a floating tenon (spline?) in the joint, then a pair of about 1/8"-3/16" deep butterfly dovetails on each side of the joint.

Hopefully this weekend i will have some time to do a test run and get a jig made up, then maybe get a few legs done up.

[Johnny Kleso]

Alex,
if you need to make many you can try machining a strip of butterflies in a TS tenoning jig and then cutting them like slices of bread if you can find wide enough stock..

Also try gluing some thin stock to plywood and then routing the shape then sand or cut the plywood off..

[Russell Sansom]

Every time I've chosen a spline, which has added up to dozens of times over the years, I've been very happy with their strength and their simplicity. Still...a couple dowels look good here.