Cap in Hand...

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Chris Hall
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Cap in Hand...

Fri Mar 23, 2012 6:19 pm

With the toolbox carcase assembled, the next matter for attention were the two caps which are fastened to the end board and handle assembly.

The underside of the caps have shallow housings to index directly onto the tongue which was formed on the top edges of both end boards and handle:
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The caps were flipped face up and the layout of the mortises for the keys, connecting the end board assembly to the cap using 5 double-wedged floating keys. This was the strongest connection I could come up with:
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The key's are 0.75" wide by 0.25" thick, and enter into the end board assembly 0.625".

I processed the cuts with the caps mounted in position on the box, using my router and a longish 1/4" solid carbide bit:
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One side done:
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The process was repeated on the other cap. Then it was time to square up the mortises with a paring chisel and guide:
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Repeat 10 times per cap:
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Here I'm giving a tip of my cap, if you know what I mean:
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Next step was to create an interior flare in the mortises, which in this instance I worked out to be a 1:9 slope. I prepared a paring block using a piece of laminated bamboo ply, and went to work:
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Then end mortises were a little tricky, needing some shimming to support the paring block properly:
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With all the mortises flared out, I prepared 10 keys, using Jatoba, and lined them up like so many ducks:
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There was a slight amount of variation between mortises and keys, so they were individually fitted and numbered:
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The keys were then kerfed and I began fitting them also to the cap mortises, to make sure they were snug for thickness most particularly:
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One end done, fitting keys to cap:
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The other end also complete:
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Then the mortises in the cap were flared out, using a 1:8 paring guide, spacing 3/64" off the end line of the mortise:
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With the cap mortising complete, I trimmed the excess length off the caps so they were close to the dimensions of the box. I'll save a final trimming of the cap ends for some planing work later on.

This key is going to hell:
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A few taps and it is seated:
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This row of ducks has certainly gone to hell:
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Then I grabbed a piece of plastic to use as a spacer and lopped off the excess material from the keys:
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The result:
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Chris Hall
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Re: Cap in Hand...

Fri Mar 23, 2012 6:33 pm

Time to pull the caps back off, using a rubber mallet in a judicious manner:
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Separation anxiety only lasts a few moments and then it is over:
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Huh!? It looks like key number 5 and key number 10 must have gotten swapped for one another by accident. It all worked fine though.

The next step was to kerf the exposed key ends for wedges:
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10 keys and 20 kerfs later, I could place the caps back on:
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Out comes a clamp and I hold the cap firmly down.

Then I apply a dab of glue to the Jatoba wedges and stick 'em in position:
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A little tippy-tapping and the wedges are down:
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One row of keys locked down:
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I immediately zip them off with my flush cut saw:
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One end all done:
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Followed by a casual swipe with a plane to clean it up a bit:
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A completed wedged mortise: the Jatoba key and Jatoba wedges make for a discrete connection in a mahogany piece:
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I guess one way I'm dealing with the more elaborate nature of this piece in comparison to the usual Japanese toolbox is that i am choosing to turn the volume down a bit on the connections, making them a little less obvious hopefully.

Well, that's all she wrote for the caps - next fun-filled episode will be the lid and its dovetailed battens:
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A last look:
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I'll take a break for a while and see if anyone forges ahead and catches me up a bit.
Attachments
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ti
timoore

Re: Cap in Hand...

Sun Mar 25, 2012 3:41 am

Why are the slopes of the cap and box side mortises different? Put another way, how did you choose the slopes?
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Chris Hall
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Re: Cap in Hand...

Sun Mar 25, 2012 9:46 am

The box sides are 1/2" thick, and the joint is flush, so the tenon penetrates through 1/2". A 1/16" flare over 1/2" distance works out to a 1:8 slope for the wedge.

The cap is 1/2" thick, however the tongue on the end board edge/handle edge assembly enters into the cap by 1/8" - thus the floating tenon travels through the cap a total of 3/8". If I use the 1:8 bevel guide, set back 1/16" on the top of the cap, it would mean that the chiseled slope would run down into the end board edge/handle edge dado, which I wanted to avoid. I could have set a new slope based on 1/16" over a 3/8" distance (1:6), however that would have involved making a new 1:6 paring guide. Instead, I determined that the 1:8 guide already made would work just fine if I set back the guide 3/64" instead of 1/16", as 3/8" divided by 8 equals 3/64" (0.046875).

And as for the 1:9 ratio used for the mortise into the end board edge/handle edge assembly tongue, my mortise was 9/16"" deep (0.5625"), and a 1/16" flare over that distance worded out to 1:9. Actually my target depth there was supposed to by 5/8" (0.625"), but I made an error somewhere in setting up the router depth. Once i discovered that, I decided to stick with the slightly shallower depth instead of setting back up again to rout deeper.

I guess it ought to be noted, that despite the precision of the cutting, some of the numbers used are a bit arbitrary. The depth for the keys into the end board edge/handle edge tongue for instance, would have been fine at 11/16" depth or 3/4" depth. The critical part is to get the flare right so the joint locks up properly when the key is tapped down.

For those feeling like the floating tenons are all a bit too much to even entertain the thought of executing, there are two simpler approaches:

-simply cut the dado on the underside of the cap and glue the cap into place - a very sound glue joint.
-cut the dado on the underside of the cap and nail it into place.

Or, one could forgo the dado and tongue set up altogether, make the end board and handle assembly flush to the rest of the box, and then nail the cap into place. That would be just like how it is normally done on a traditional Japanese toolbox. I have no problem with anyone doing that. The floating keys with double wedging are a metal and glue-free solution to joining the cap, and joining the cap is actually the trickiest piece of the entire joinery puzzle with this box. The joinery solution I arrived at is not the easiest to actually execute, so I don't want to discourage anyone from making the box if that joinery seems too daunting. If you've haven't done much joinery, then the multiple mortise and tenons used to connect the box walls together are adequate as a challenge.
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Dan McC
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Re: Cap in Hand...

Fri May 04, 2012 11:41 am

Chris,

Wondering how wide the caps should be? One side I know is flush with the end of the box, how much should the other side hang over inside the box?

Kind of related to that, how long should we cut the lid to, and where should the battens be positioned relative to the ends of the lid?

Dan
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Chris Hall
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Re: Cap in Hand...

Fri May 04, 2012 4:51 pm

Wondering how wide the caps should be? One side I know is flush with the end of the box, how much should the other side hang over inside the box?

Kind of related to that, how long should we cut the lid to, and where should the battens be positioned relative to the ends of the lid?
Dan,

I've been wondering when someone would ask!

I will give you a thorough reply before the weekend is out. There isn't a fixed answer to your question, only extremes to be avoided.
djwong
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Re: Cap in Hand...

Sun May 06, 2012 2:43 am

I made my cap 2.75" wide. We had a little discussion about it in the "Preliminaries..." section. I just finished cutting all the mortises in the cap. Still have to cut the slopes in the mortises and make the wedges, then on to the lid.
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Dan McC
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Re: Cap in Hand...

Mon May 07, 2012 4:39 pm

DJ,

How did you cut the mortices in the cap and ends? I don't have a plunge router and my regular router doesn't have a fence in any case. I am thinking maybe on my horizontal mortiser, or with the drill press. I've measured and remeasured and marked and remeasured their location, but not much room for error cutting into the relatively thin tops of the end and handle! I'm feeling more nervous about cutting these than any part of the project so far. I'm toying with the idea of changing the mortices width from 1/4" to 3/16" just to give me a bit more wiggle room.

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Chris Hall
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Re: Cap in Hand...

Mon May 07, 2012 5:21 pm

If you're nervous about it, perhaps it would make sense to make up a couple of extra caps and do some mortises on those, adjusting until you have the locations correct. Do the mortises on the caps, fit them in place, and see how things look.

Shrinking the mortise width down a 1/16" would be fine, but I think if you cut the caps first, then you can mark out onto the top edges of handle and end board directly from those mortises and see where you are sitting.

One of the reasons I like to use a digital caliper is for close fits with little room for error - like this one.

And, well, it looks like you have your caps cut so do you still need a run through on that detail?
djwong
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Re: Cap in Hand...

Mon May 07, 2012 5:41 pm

Hi Dan,

I did cut my mortises with a plunge router and a 5.5mm (7/32") uncut spiral bit I have. I indexed the router with an edge fence along the outside edge and made a series of plunge cuts to hog out the mortise. I then made several passes to get the width close to 1/4". The router bit tapered slightly, so I still had to pare the sides using a 1-2-3 block as a guide. While routing, I clamped the cap to the box, so it would not accidentally shift of come loose. I triple checked my measurements, did not rush, and went slowly, left some margin for error by cutting within the layout lines. My second set of mortises was definitely better than the first five.

You could also cut the mortises in the cap and sidewalls separately. I cut the mortises in the interior partition this way, mostly with hand chisels.

David

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