Making butterfly keys

[Jeremy Rayburn]

I would like some input on what you feel is the best way to make butterfly keys. So far, I've made a jig for my bandsaw that seems to cut a pretty symetrical key that I am happy with. However, I am having difficulty getting a good fit when I cut the mortise to take the key.

I have been marking the outline of the key with a knife, mortising out the majority of wood with a plunge router, then trying to clean up the edges with a chisel. This seems to be a pretty standard installation method, and maybe I just need more practice to get it tight, but I'm listening to any other ideas out there.

[Conrad Fiore]

Jeremy,
The way you are doing it is correct, just take your time with the chisel and pare inside the lines and test fit often. You can also pare the sides of the butterfly with the chisel if you need to shave just a bit off for the perfect fit.

[Dewey Torres]

Jeremy

May I suggest you try a router inlay kit?

It is basically an almost flawless 2 part process that yields results which don't need tweaking.

Also, you use the term "keys" which normally refers to a butterfly that is used to join vs. decorate. I am assuming you are asking about inlay though (?)

http://www.hartvilletool.com/product/11208

[John Eaton]

+1 on the router inlay kit - makes things super easy.

-- John

[Jeremy Rayburn]

I actually plan on using the butterflies over a pith crack I have in a walnut slab. So whether it's a key or inlay, same method right?

[Dewey Torres]

I actually plan on using the butterflies over a pith crack I have in a walnut slab. So whether it's a key or inlay, same method right?

Yes... same method

[Hank Knight]

Try paring the edges of the butterfly insert so it's ever-so-slightly narrower at the bottom than the top (I.E., wedge-shaped). Then apply a little force to seat it when you glue it in. The sides of the mortise will give a little and the result should be a seamess fit.

Hank

[William Hamilton]

I've done my share of butterfly keys already, and I've found the key (very punny) is cutting the keys with a very small inward angle on the sides and ends. I usually cut my keys on the bandsaw. There you can pitch your table 1 degree or 1/2 degree and make your cuts. Just make sure as you turn your piece while cutting it, ie. that your angle is going IN to the piece, not in the opposite direction. If you don't want to angle them on the bandsaw I've also done cruder bevels with a dremel tool, or even an upside down belt sander. You just want a very faint taper. It's also a good idea to slightly round off the bottom corners. This can prevent possible damage to your mortise when test fitting and hammering your key in.
Be sure to flip over and trace the TOP of your keys on your work piece, not the bottom, since the top of the key is what is going to line up directly with what you're cutting out. Always score just inside your marks with a marking knife. Rout in steps, as usual. Keep your chisels at 90 degrees when cleaning up your mortise. I chisel the sides first, then the ends and corners. Use the widest allowable chisel, starting with the edge in your mark, and then slightly overlapping each pass.
I make my keys so they'll rise up out of the mortise a good 1/16", the rest can be sanded down after gluing. My keys are usually 3/4" in thickness. Some guys use thinner keys but IMHO to give it more strength I go thicker. Plus if you have a check or something that's visible from the side, it looks cooler to see this thick key going down.
I use a 2-part epoxy and coat the entire mortise. Nakashima was also known to bury a brass screw up from underneath the workpiece into his butterfly keys. I'm assuming this provided even more stability.

[William Hamilton]

two other things (forgive me if you know this already, maybe a newbie will find it useful).. use a wood block over your key an a wooden mallet when hammering it in, otherwise you can really damage your key and then you're S.O.L. Be sure the grain of your key is perpendicular to the grain of the workpiece you're putting it in. That helps with keeping it nice and strong and it won't split your workpiece.

[William Hamilton]

one last thing.. I just tried a new technique last night and it worked like a charm. Cut out the middle man, and instead of tracing the top of your key onto your workpiece with a pencil and then scoring that, simply trace the key carefully with an xacto knife or something of that sort. Then remove your key and trace the score in a bit deeper. This line is EXACTLY the size of your key. When you chisel out the edges, just set your chisel edge in this little score, and it cuts out perfectly and fits perfectly.

[Chris Fournier]

I've made two sets of jigs to make and mortise 3", 4", 5" and 6" butterflies. I made the mortising jig on the table saw out of four pieces of wood, settin the blade to the key angle - very accurate. I then made the key pattern using the same TS set up. I make my keys over thick, screw them to the jig and then machine them to the pattern with a router. I install the keys with the screw holes down and plane flush to the surface. The keys need a small amount of chisel work at the "waist" to get a crisp intersection and what a great fit with the mortise! Perfect keys. The whole set up took less than an afternoon to make and the results are predictable and tidy every time. Leave the mortising jig quite overlong so that you can clamp it to the work surface without interference when you're routing the mortise.

[John Baum]

In 1979, two friends and I felled a dead urban American black walnut. It was 4’ in diameter at the soil line. The homeowner wanted to turn it into firewood. Two of us paid him $100 a piece for the privilege of felling it. Using a friend’s chain-saw mill we cut it into ~ 12/4 rough sawn planks. We then shared in the proceeds. Damn, the pieces are heavy. The sapwood was infested with beetles, but they pretty much stayed out of the heartwood. Enough about the wood.

Today I want to work with some pieces that I have milled to 10/4. They are taken from branches; therefore they are reaction wood. There are checks I would like to stop with butterfly keys. I have some questions about the technique.

Since George Nakashima set keys (even keys made with different species of wood) with the grain at right angles to the grain in the plank, I gather that this is a time tested exception to the rule that we should not attempt to permanently fasten pieces of wood with their grain running at right angles to each other without allowing for movement. People talk about gluing in the keys in this thread. Is it the case that a small key in a larger plank is different enough from the case of two similar sized pieces that this butterfly key technique works and is recommended?

Is there an advantage to using black walnut keys with black walnut planks?

In my project, some of the pieces will be ripped to 3/4 to 4/4 thickness. Are there rules of thumb regarding the dimensions of the key (overall size and relative thickness) for using keys to stop checks from migrating further? I’ve seen everything from ‘through’ keys to inlaid keys. Is there any prevailing wisdom regarding what works in the long run?

I am sure I will think of other questions as I get further into this project.

[John Nesmith]

I've done a few with a router kit. They all came out perfect. I can't imagine an easier method.

[Lee Schierer]

Jeremy

May I suggest you try a router inlay kit?

It is basically an almost flawless 2 part process that yields results which don't need tweaking.

Also, you use the term "keys" which normally refers to a butterfly that is used to join vs. decorate. I am assuming you are asking about inlay though (?)

http://www.hartvilletool.com/product/11208

The small router bits that come with the inlay kit break easily. Order a spare bit if you go this direction. Also, a 1/4" bit to hog out the bulk of the material then go back and clean up the edges with the 1/8" bit. You will still need to clean up the corners of the mortice.

[Dale Osowski]

Patience and sharp tools will get you good results. The more you do the easier they become.