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Butterfly Key Joinery - Part IV
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Welcome to the final post in the butterfly key joinery project series.  If you missed the first three entries:

Butterfly Key Joinery - Part I

Butterfly Key Joinery - Part II

Butterfly Key Joinery - Part III

In Part III, I laid out the mortises, rough-cut them with a plunge router, and cleaned up the edges with a chisel.  This week, I checked the fit of the keys in the mortises and installed the keys.  In the process, thought of a couple of things that I should have clarified on the subject of cutting the mortises:  I said that I routed the mortises in three passes, 1/4" at a pass, to get them ready for the 3/4" tall keys.  I routed the mortises in three passes mainly because it's easier to control the router in a shallow cut - I doubt that it would have been a burden for the 3 -1/4 HP plunge router if I'd have cut the entire depth in one pass.  Also, it would have been more accurate to say that I routed the mortises in two passes that each took off roughly 1/4" of material, and one pass with the router set to depth of 1/16" less than the height of the keys.  I made the mortises a little shallow because the corners of the keys near the very top break easily, and I think it's asking for trouble to cram them all the way down flush with the surface of the receiving material.

The first step in installing the keys was to get an idea of how well they fit into the mortises.  To do that, I checked to see that each key would slide down into its corresponding mortise about half way without my having to put much pressure on the top of the key.  With the keys in the mortises, I checked to see whether there were any large gaps between the key and the mortise that might show up in the finished product.  Part of what tapering the key does (see Part II and Part III of the series) is make it so that the key gets wedged into the mortise at the top of the joint.  The mortise / key joint is a "compression fit", in other words, and very small gaps and inconsistencies between the shape of the key and the mortise get forced into alignment by the pressure of the fit when the key is finally installed.

Any gaps that are the thickness of a matchbook cover or more, on the other hand, can cause problems in the finished fit of the joint. Usually, if I've taken care to get the right shape of key, the right taper from top to bottom of the key and I’ve laid out and cut the mortises using the procedure I described in Part III, I end up with mortises that are a little on the tight side to begin with, and can make slight adjustments in either the keys or the mortises without ending up with a loose fit.  It's important, I've noticed, not to cram the key into the mortise to see how well it fits - it's been a challenge on a couple of occasions to get a key out of a mortise without damaging either.

After a few minor adjustments to the shape of the mortises, I had a key / mortise fit that I was reasonably happy with.  I made sure that I hadn't left any chips in the bottom of the mortises and made sure that I'd gotten the corners of the mortises as square and clean as possible (I always round off the bottom corners of the keys anyway, to make sure there won't be any problems where the corners of the keys meet the corners of the mortises).  Finishing that, I was ready to glue the keys in place.  If parts fit together well, you don't need to use lots and lots of glue, (if they don't fit well, glue won't cure the problem anyway).  I just coated each side and the bottom of the key with a film of glue and tapped them into place, using a block of wood to protect the top of the key.  You can see here that even though I used the glue sparingly, I got a fair amount of squeeze-out around the top of the joint.

After the keys were glued in place, I wiped off the excess glue and set it aside to dry.  The next day, I took off most of the 1/16” or so of the keys that sat proud of the surface of the jatoba with a block plane, and finished leveling the surface with a scraper.  The only thing I'd mention here is to be sure that the plane is sharp and that you are careful to keep it flat on the surface of the key.  You also need to understand that wood almost always planes better in one direction or the other, depending on the direction of the grain.  If the plane is leaving a rough surface, or it’s hard to get the plane to go across the surface, flip the piece around and plane from the other direction.  The purpose of using a cabinet scraper to finish off the job is that at some point in the process, you'll have to run a tool diagonally across the grain of both the key and the receiving material.  With a sharp cabinet scraper you should be able to go straight across the grain of a piece of wood without causing damage.

That's the butterfly key process, essentially (or at least my process).  All I have left now is to think of a way to use a split piece of jatoba that I've spent some time repairing.

posted on June 15, 2006 by Rockler
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13 thoughts on “Butterfly Key Joinery - Part IV”

  • Michael Dodds
    Michael Dodds June 8, 2007 at 9:36 pm

    You should try the drill press...Cheaper than a 5 speed Kitchen Aid, and the cordless may go dead. And you can clamp the bowel down while you go for a cup of joe...

  • Blog Editor

    That makes sense, except that dragging a 300 pound machine all the way to the kitchen every time you want whipped cream seems like a lot of work.

  • dave

    Next time use a fork. Take a cheap pressed steal fork and bend the "shank" length wise. into a v type shape. then mount the fork in a chuck of a cordless drill (18.0 v)and bend the fork spikes in alternate directions. This way you cut down on the cost. IT WORKS!

  • Blog Editor

    Sounds good, Dave, but it's a little hard to picture exactly what you're describing. Do have shop drawings or a plan that we could look at?

  • Go buy a hand egg beater, cheap. You know, you turn the crank and two beaters spin. They're faster than your mothers toaster and tougher than an escaped gerble.<br />Mine doubles as a comb and a paint stirer.

  • I'm a fan of many woodcrafters and comedians, Tim Allen, Norm Abram and many others....Tim wouldnt even try this.<br />All that I can say is wow...WOW.

  • Gretchen Lafaso
    Gretchen Lafaso January 10, 2008 at 1:26 pm

    This past Thanksgiving I was stuck in a similar situation. Needed egg whites whipped up and in the last week I had lost to desease both my kitchen aide and my hand mixer. So I tried the cordless drill with one hand mixer whip. Didn't work. Just one spinner doesn't draw enough air in to whip the suckers up. Since then I bought a cheep hand mixer. But if stuck in that situation again maybe my cordless and my plug-in drill duct taped together? Or... now that I think of it the kitchenaid whip probably would have worked.

  • Geof Tyson

    Thanks for the detailed instructions.<br /><br />I have 2 beautiful free-form 6' sister slabs of 2 1/2" black walnut with both having matching 18" long cracks from air drying. <br /><br />I want to make coffee tables for my 2 daughters and am trying to develop a unique three-legged base.<br /><br />I was planning on using rosewood keys to offset the walnut tone. However, after seeing what could be done with curly maple I'm going over to the planing mill to see if I find a small piece for high contrast butterfly keys.<br /><br />Thanks for the step-by-step.<br /><br />You've made a daunting task, a pleasure.<br /><br />I do have one double-edged question. With this thickness, I really feel that it may not be a necessity. (what's your take?) Regardless, I now feel comfortable with using butterflies but how thick should they be set? (3/4", 1",<br />1 1/4" or ...) <br /><br /> Your help on the thickness would be greatly appreciated.<br /><br />Geof Tyson

  • Carl

    Geof,<br /><br />Thanks - glad you found the information useful. <br /><br />Sounds like an interesting project. Ideally, keys on both sides of the material would be best - similar to when veneering it's recommended that you veneer both sides of the substrate. It's more work, of course, but the under-side keys don't have to be as perfect. The keys don't need to be all that thick. Especially if you do both sides, 1/2" would be a great plenty, I'd think.<br /><br />If you have pictures of the project at any stage, we'd love to see them. <br />

  • Lisa

    The part of me that is married to a man who would do
    something like this finds this story highly amusing.

    The part of me that has territory issues about my kitchen
    finds this story a blasphemy against the Kitchen Gods.

    However...given that I have hand whipped whipping cream
    myself a time or two and have a soft spot for power tools and the men who
    wield them allow me to suggest a realistic alternative to a
    Mixer: Dremel tool. ;-) The speed is about equivalent to that of
    a mixer but it suits the testosterone set much better.

  • Rockler Blog Team
    Rockler Blog Team September 14, 2009 at 1:25 pm

    Thanks for the comment. You may be on to something: compact, maneuverable and easy to store, a Dremel tool might be just the thing. It might even go unnoticed by the Kitchen Gods.

  • Vinny

    Routers? Forks? Cordless drills? Hand beaters? Sounds like way too many years spent watching "Tool Time" reruns. lol Virtually every supermarket and retail drug chain sell inexpensive no-name kitchen appliances. For probably $10, you can purchase a 2-speed electric hand mixer with beater bars. Granted, it'll be cheaply made - no doubt imported - but it'll be just as good and a whole lot faster than even the better hand beaters. If the mixer's primary task is to occasionally whip egg whites or heavy cream, it should last many years. However, if mixing cake batter is expected of it, it's limited 2 speeds most likely will produce cakes with poor texture and probably burn out prematurely. Now, if you're a kitchen purist, why not gild the lily and buy a French balloon whisk and round-bottom copper bowl? In a matter of minutes, you'll have stiff egg whites, a smooth zabaglione or nicely peaked whipped cream.

  • uggs outlet

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