Japanese Puzzle Box - #5 Dovetail, Slot, Slider & Recess for Lock Mechanism

With the dividers done and in place I could go back and work on the front-end piece.  I resumed work by cutting a dovetail dado in it for the slide/latch that will get built later.

The dovetail dado is ¾” wide and I could cut that in a single pass if I had a 14 degree ¾” wide bit which I don’t.  I do have a ½” wide bit so used that and made two passes.  Setting the depth is the most critical aspect of this cut.  It needs to be exactly the same thickness as the facing layer.  Too deep and the slide that goes in it will hit the sides.  Too shallow and all the top layer will not be cut away.  Adding to the stress is you get only one chance at the cut because the edge has that 14-degree angle.  A too shallow cut with a second deeper cut will leave a little step where the bottom meets the angled side.  Needless to say, I did quite a bit of measuring and testing before making the cut as I already had a lot of work in the part and did not want to mess it up.  I set the router fence for the proper distance and made the first pass giving me a ½” wide cut.  Resetting the fence to take off an additional quarter inch and running the pieces through completed this operation.

I have one more operation to do to the front, an opening in the center of the dovetail cut for the key to slide in.  This is perhaps one of the easier things to lay out as there is more tolerance on its location and size than many of the other milling operations.  Once laid out I put a Forstner bit in the drill press, set up the fence and set the depth stop so that the tip just comes through the back side.  I do that to keep from blowing out the back as the bit exits.

Flipping the piece over I center the drill where the point came through then lightly drill to connect to the original hole.   Frequently I end up with a small disk where the two come together like shown here.

To smooth the opening out first step is to use a chisel to trim off the points.  This removes most of the material but leaves a bit of a rough surface.

Final work to clean up is done using a rasp and sandpaper.  Once done I could put the piece back in the box to check the alignment with the key-way in the piece below.

Next is to make the piece that will slide in the dovetail dado I made earlier.  This sliding piece has to match up just right with the dovetail.  Not too tight, not too loose, the thickness needs to match the depth of the cut and the dovetail angles need to match.  Also, I would like the grain to flow across the slider and match the rest of the front.  I mean if I am dreaming I might as well wish for everything.

I start by going through the leftovers from the original boards.  I found a couple pieces that are from the same board the front came out of and they look like I can get a good grain match.  The final thickness of the slider is right at 1/8”.   To give myself a little room for error I decided to make the blanks a little thicker.  My leftovers were about 3/8” thick so I set the bandsaw up, ripped the pieces then took them down smooth on the thickness sander.  Since that process has been done earlier no need to go through it again.

I still had the ½” wide dovetail bit in the router so it is simple to cut the first dovetail edge, just hold it up next to the fence and make the cut, right?  Well, not quite.  Since the pointed tip of the cut made by the dovetail bit is down on the router table and runs against the fence unless the fence is absolutely tight against the table with no gaps at all there is a good chance the piece can slip under the fence and I won’t end up with a good clean straight edge.  The solution is to use a spacer to raise the piece so the edge is against the fence and adjust the cut height of the bit accordingly. 

Now with one edge done I very carefully measured the actual width of the base of the dovetail dado then added a smidge.  A smidge is a technical term for less than 1/64”.  With that measurement in hand I ripped the slider to width using the table saw.  After that it’s back to the router to cut the second edge making sure the correct side is up.  I want to end up with angles that intersect (a dovetail) rather than parallel angles.  Don’t laugh its happened before.

When I did the first test fit the slider was close but not surprisingly just a tad too wide.  Since it is so close I have two options.  I can sand the beveled edges or the back of the piece.  If I sanded the back I was concerned that I might take a little more off one side or otherwise mess up the geometry of the piece.  In this case I felt that I would have better luck sanding the angled or the dovetail edge.  To do this I carefully balanced the slider on the 320-grit sandpaper I had stuck to granite tile and made a few even passes across it.  A test fit showed progress with a couple more rounds giving a fit with just enough friction to hold it in place.

While the slider fitted the dovetail dado just fine it was a little thick.  That’s easily solved by running it through the thickness sander taking off a little at a time until it stood just proud of the rest of the front.  I will take it down flush when I do the final sanding.  The vertical pencil lines on the slider are my marks for cutting it to the finished final length.

The next step is to route a shallow 1/16” deep recess in the back of the Slider to mount the Key in.  I needed the recess to be centered on the notch I had cut in the divider.  Here is what a vertical section through the box looks like.

I changed the router bit to a ¼” straight one then on the fence marked a line to be used as my starting point.  It is the distance from the recess edge to end of the slider.  A second line using the other end of the slider as reference gives me my stopping point for the length of the cut.

To route I line up the left pencil line with the line on the fence and lower the piece onto the spinning router bit.  When the bit is cutting full depth, I pushed the piece to the left until the right line on the piece lined up with the pencil line on the fence.  The distance between the lines on the slider and the one on the fence is the final length of the recess minus the ¼” diameter of the router bit.  The tape on the left end gives me something to grab so I can easily lift the piece off the spinning bit.

Flipping the slider over shows the finished recess ready for the key.

Next Up – Fitting the Key, Final Sanding, Finishing & Assembly

Japanese Puzzle Box - #4 Adding a Handle to the Small Chisel

The smallest chisel I used to clean out the recess started life as a metal working chisel.  I originally made it to clean up the bottom of grooves for ¼” thick maple plywood door panels.   That’s because a ¼” piece of plywood is not a quarter inch thick, it’s a tad less.  That meant I could not use my usual Japanese laminated ¼” wood chisel.  I did have a two ¼” metal working chisels so decided to take one and modify it to meet my needs.  I ground the width down to 3/16” wide, reground the cutting angle then sharpened it to a razor edge and it worked great.  Almost great that is.  Without any type of handle after using it for a while the small butt end left my palm sore and bruised.

Using it on this project was the last straw.  It’s time to make a handle for this tool.  I had some 2” thick cherry scrap left over so cut this blank out and marked the center on each end for mounting in the lathe.  You can see the chisel setting next to it.

 

Next is to punch the marked centers on each end and mount it in the lathe.

A couple of minutes of turning and I had the piece nearly round.  Here is one of the original flat faces not quite gone showing I need to take a little more off.

A little more work and I had the piece round and the beginning of the handle’s taper.

As I was turning I noted that the heel end (left side) of the handle was wobbling a little bit.  That told me that it was not quite completely square with the axis of the piece.  The cure is to:

1. Remove the blank from the lathe.
2. Take out the drive spur.
3. Install a 4 jaw chuck.
4. Reverse the blank.
5. Clamp it in place using the 4 jaw chuck and the tailstock live center to register the heel end so the blank is centered.
6. Pull the tailstock back away from the blank to give working room
7. Turn the heel face square with the center axis.

Here you can see I left a little nub on the squared heel so I could use the existing center dimple for axis alignment if I needed it later.

I will be mounting the blank using a screw later so I need to drill a pilot hole on axis.  I used the drill press for this.  Here is the setup, the hole in the MDF is for the nubbin on the heel to set down into.  I can now use the rim of my newly squared heel as my reference surface.  It’s then a simple matter of setting the blank in place and drilling the hole.

With the mounting hole drilled I put the blank back on the lathe and turned the nose end down to its rough shape and close to final end diameter.  The tail stock helps hold the piece centered on its axis.

In order to turn nose to final diameter I needed to pull the tailstock away.  Here I am with just the softening radius left to do at the end of the nose.

Once the nose end is nearly finished I could get ready to turn the heel end.  To do that I use a shop made adapter.  It is a 7/8” diameter by 1½” long piece of oak that has a centered pilot hole counter sunk for a screw that will run into the nose.  The adapter gets clamped in the 4-jaw chuck and the heel is aligned using the tail stock.

I can now turn the handle to its final dimensions except for a little nub on the heel end. 

 

Using a thin parting tool the nub is parted off, the tail stock pulled out of the way and final sanding done.  The handle is now just about ready for finishing.

The last tooling operation is to cut a couple of small grooves in the handle then with the lathe running use a piece of wire held in the groove friction burn it.  An application of Danish Oil Finish brings me to this point.

I did not take a photo of the adapter earlier on when I was mounting it to the handle blank, so here is what it looks like as I unscrew it from the finished handle.

My next step is to enlarge the pilot hole to snugly fit the chisel then epoxy it in place.  Before I drill the hole, I need to check to see how much clearance I need between the nose of the handle and cutting edge of the chisel so it will still fit in my sharpening jig.

Now that I have the hole depth I can set up the drill press to drill the handle.  The piece of tape on the drill is my handy-dandy depth gauge and the piece of MDF is the same one I used earlier.  It is set up centered on the drill bit then clamped in place to stay put.  This is to assure that when I drill the hole it will be on axis, square and not misaligned.

Last is to mix up some epoxy and glue the chisel in its new home.  All done it’s a lot easier on the palm of my hand to use than just the steel chisel.

Next Up – Dovetail, Slot, Slider & Recess for Lock Mechanism

Japanese Puzzle Box - #3 Sides, Dividers & Start of Ends

Before I get started with the next step in the project I have been asked how many people look at this blog.  The statistics show there are currently about 900 hits a month to the site from 30 countries.  This is way more than what I thought there would be when I started.  I thought my audience would be some of the people I knew who did woodworking and maybe a few others.  In total, probably no more than a couple dozen.   I never dreamed that two-thirds would be from outside the United States and over half from areas where English is not the primary language.

Now that I had the top mostly done I could move on to working on the sides.  The first group of cuts are set up all the same ending up with this groove around the perimeter.  This leaves the two stopped dados laid out in pencil to cut. 

The first is pretty simple, reset the fence then mark the limit of the cut by measuring from the leading edge of the bit minus its diameter and drawing a line on the fence. 

With that done I can route the dado until leading edge of the piece hits the line then carefully back the piece out.

The other dado is a little more difficult.  If I try and cut this one like the first I would come in from the left which because of the router bit rotation would not pull the piece into the fence but try and push it away.  I might be able to make it work but the probability of a problem goes way, way up.  The method I will use is to lower the piece onto the running bit then cut away until the bit exits the wood on the right side.  The starting point is marked on the fence as the distance from the leading edge of the bit to the edge of the board.  Here I am lowering the piece onto the spinning router bit.

Here is the finished side, all cuts are made with the same 1/8” router bit the only change being where the fence is set up.

I can now do a test fit on the side and bottom.  It would not quite go together without using more force than I was comfortable with so I did some light sanding and then the joint fit together snugly.

 

After getting the sides and bottom joints to fit I moved on to the two dividers.  There are tenons on each end that fit into the stopped dados on the sides.  They are cut on the router table using the 1/8” bit.  Once glued to the sides and bottom they provide the structural rigidity for the box.  The front divider also has a notched recess that is a part of the locking system.

This notch has to be very carefully laid out and cut into the divider.  To eliminate the chance of cumulative error in measuring I needed to take all my measurements from the same edge.  To get those measurements I did a quick sketch of the notch then added the individual dimensions together.

I started by putting blue painters tape on the divider.  Then using a dial indicator caliper transferred the notch layout to the piece.  Rather than use a pencil with it’s inherent inaccuracy for layout I used a marking knife to cut the blue tape.  Once done I peeled the cut tape away leaving me a clear dead-on accurate layout for the notch.

Before cutting the notch, I did a dry fit of all the pieces I had cut to see if there were any problems.  The top has to slide smoothly and did hang up in a couple of places but some light sanding made it fit just fine.

I could now start cutting the notch but when I went to get the ¼” Forstner bit needed I found my set only goes down to 3/8”.  On a sample piece, I tried some different methods of cutting the notch but had absolutely no luck in even coming even close to finding a good alternative.  Checking around town nobody had that size bit, the smallest was 3/8”.  Going on-line I found I could get one from Home Depot delivered to the house but the shipping cost as much as the bit.  The other alternative was to have it delivered to the local store for free with me going in to pick it up.  The minor downside is that delivery is a few days out, but I went ahead and ordered it.

While waiting for the bit to arrive I started working on the ends.  The back has some locking rabbit joints like the top and bottom.  The front has the same locking rabbit joints plus other machining for the locking mechanism.  More on that later.

I started by cutting my rough blanks to final width and length then using the router cut the locking rabbit joints on the two side edges the same way as I did on the side pieces.   For the back an additional dado at the top and a wide rabbit at the bottom completes it.  At this point the front gets a rabbit at the bottom.  With all the routing done a test fit showed a small amount of fitting needed since these pieces have to slide as a part of the puzzle. 

The front part still has a fair amount of work to do to it before it’s done but the same day I finished the initial fitting I got an email from Home Depot saying the ¼” bit was in and ready to be picked up.  With the bit in hand I will set the ends aside and go back to working on the dividers.

After chucking the bit in the drill press I set the stop so the hole depth is just short of the final depth.  Next is to set the fence so the bit is right at the cutout in the blue tape.  The fence keeps the holes perfectly aligned as I move the piece to drill overlapping holes.

 

Shifting the fence slightly lets me drill the second row of holes.  It almost seems anticlimactic to wait on the drill bit and then in a few minutes drill just 8 holes in each of the two boxes. 

Taking the part from the drill press and clamping it to the workbench I used a variety of hand chisels but mostly a small one without a handle.  Using them I cleaned out the recess until it was ¼” deep with a flat bottom.

Drilling the holes just short of the final depth gave me some room to clean up the bottom of the recess and get rid of most of the marks left by the bit.  It did take a little longer but looks better.

Here is the box reassembled with the completed divider in place.

Next Up – Adding a Handle to the Small Chisel

Japanese Puzzle Box - #2 Glue-up, Establishing Final Thickness, Top & Bottom Routing

With the pieces smoothed I went back through them checking for flaws that may have come to light when ripping and sanding.  Seeing no problems I marked them up showing what parts came out of each blank.  I should mention here that the next couple steps are required only for the leopardwood.  That’s because I did not have any raw material wide enough for the box so I have to glue up pieces to get the proper width.  I also let all the pieces set for a week or so to make sure they are stable.

Next I set up a stop block on the chop saw and cut the blanks into the required lengths that will be glued together to form the parts for the puzzle box.  I use a stop block since it allows me to carefully measure once and cut matched pieces all day long.

From there I spent time shuffling the individual pieces around in various combinations until I ended up with the best grain alignment I could get so the joints would be all but invisible.  Now I can rip the pieces to the appropriate width and start gluing them up.  One of the truths in woodworking is that you can’t have too many clamps and I pretty used up all that I had in this size to glue all these six pieces up.

After letting the glue cure overnight I took the clamps off and brought the maple pieces back into the work flow.

Checking the thickness of the pieces I see that I am just a little over 1/16” too thick my target thickness of 3/8".  They were ripped this way in case they moved after cutting so I had some excess if I needed to flatten them.  As it turned out everything was in pretty good shape.

After running the pieces through the thickness sander and keeping a close eye on their thickens I hit my target of .3775”.  Before I get a lot of notes that 3/8” is not .3775” but .375” I know that and there is a reason the pieces are two and one half thousandths too thick.  The finest grit I have for the thickness sander is 220 and that will not give me the surface smoothness I want.

To get both the surface smoothness I want and the required thickness I used some spray adhesive to mount some 320 grit sandpaper to a flat granite tile and sanded each piece smooth. 

That got rid of the 220 grit sandpaper scratches and brought the thickness down to .375 or 3/8”.

With all the pieces to the needed thickness I started cutting them down.  Some are to exact size and some are slightly oversize depending on how I see the milling process proceeding.  To make sure I know what piece has been cut how I write myself notes!  The two long pieces at the bottom of the photo have been through the same thickness machining process as the others and will be used for testing equipment setups prior to cutting the actual pieces.

Here is what the top piece for the leopardwood box looks like at this point.  Note that it is glued up out of three pieces.  How easy can you find both the glue joints?  That’s the result when you take the time to do careful grain matching of individual pieces.

Next is to start routing the locking rabbit joints in the top and bottom.

Most of the joints in this project are going to be made using the router table and a 1/8” diameter router bit.  The locking joint is cut first with the piece on edge and then laying down.  To help hold the piece tight to the router table fence on edge I first reached for the magnetic jig I use to apply pressure when cutting on the bandsaw or the table saw.  About that time, it dawned on me the router lift top is made from aluminum and the magnetic jig would not work. 

So now the first step here is to make a feather board.  Not that hard, I cut a scrap pine board at a 30-degree angle then cut flexible fingers using the table saw.  These fingers will provide the pressure to hold the piece vertical while I do the routing.  Here is what it looks like in use.  Just out of the photo are a couple of clamps holding it in place.

To start I put the bit in the router and set the cut for 1/8” deep.  The full depth of this cut will be ¼” but I think that’s too much for such a narrow bit to cut in one pass.  My rule of thumb is to cut no deeper than the diameter of the bit.  So, a 1/8” bit has a maximum depth cut of 1/8”.  Here what the bit set for the first 1/8” cut and then for the second additional 1/8” pass looks like.

 

The actual cut is pretty easy.  All I need to do is press the piece down onto the table and gently feed it through.  The actual feed rate is a matter of experience.  It’s all dependent on router power, cut depth, material and router bit.  Too fast and cut quality will degrade, bit may break or router will bog down. Too slow and the wood will burn.  Here it’s not a matter of power but fragility of the bit and the wood being cut.  The leopardwood piece is easier than the curly maple.  Both are hard but the same characteristic that make the maple curly causes a lot of wild grain that also varies in ease of cut.

With the first cut made I reset the fence on the router table then made the second cut with the pieces lying face down.

When done, here is what the locking rabbit joint looks like in the top.  This piece also has a locking joint on the end.

 

I had just one more cut to make on the top, a 7/16” wide dado on one end.  I could have used the 1/8” bit and made several passes but wanted to minimize its use to reduce the chance of breaking it.  Instead I changed the bit out to a half inch diameter one.

Here is what the finished cut looks like along with the setup.  I use the piece of plywood on the right of the curly maple to back up the cut to help reduce the potential blowout of the end grain cut.

 

Next Up – Sides, Dividers & Start of Ends