Monday, February 29, 2016

A Ming-Inspired Cabinet (38)

Work on the web frames for the lower part of the cabinet continues....

The pockets on the center boards which receive the sword tip miters are chopped:

Another one underway:

Getting closer:

At this point, a paring guide is brought into play. Well, two paring guides actually:

I set one guide up by eye as best as I can, and then tap the other guide over to meet it. At the moment that the line of light between the paring guide miter tips is closed off, I figure I have them where they need to be:

Paring can then be tackled - after a sharpening session of course:

This one looks done:

By design, there is a reinforcing rib formed inside the joint immediately behind the reentrant miters.

Another one pared, same routine as previous:

The paring guides seemed to do the trick.

With a clean result on the first board, I then processed the roughing cuts on the remaining boards:

A while later, all miters had been pared to the line on all the boards:

Then it was back to the front 3-piece rails, of which there are 4 sets. The center pieces had not been spear-pointed at all yet, and the end pieces, which had been spear-pointed, yet had been left fat of the line by about 1/16" (1.6mm). I wanted to have room to maneuver.

So, the same paring guide could then be applied to these parts as well:

Time to try a fit to see how things are looking:

The clamps are holding the board to my planing beam. I also used a clamp to draw the joint fully tight.

At this point of the process I am moving with caution, not having 'proof of concept' yet as far as the cut out approach goes, not sure if the paring jigs are on the money or not, etc.

The next front rail piece can be fitted:

After checking that the front rail pieces were in line with one another and square to the receiving board, I had the connection together:

Almost there with the miters, it would seem:

Another tweak brings it closer -you can see by the pencil mark which part I adjusted:

Then I scuffed the surface with a sanding block and 220 paper just to clean up any slight irregularities where the miters met one another:

That was looking decent I thought. I can set it aside once I complete one last task on it - the mortises for the parallelogram-shaped keys which lock the joint need to be established.

The shachi sen mizo were marked out on each stick when the joint was assembled, and then the joint was separated, layout completed, and the trenches could then be cut out, first sawing then paring:

After cutting was mostly there, I reassembled to see how that looked:

Wishing I had used 320 or 400 paper instead of 220. Tomorrow is a new day though....

While the joint was apart I noticed a slight area of interference inside the joint, so I cleaned that up and that allowed the 2-way spear point miter to draw just a hair tighter perhaps.

The gap at the end of the rod tenon is a hair more than I had planned, but acceptable:

These joints are located under the drawer's runner piece and is not viewable unless the drawer itself were to be removed entirely.

The other side:

These two are pretty close. Now that I have  them together I can do some final clean up on the parallelogram through mortises.

The last picture is a hair blurry - sorry about that:

I was trying the 'Super Macro' setting on the camera, and must have done something wrong when I clicked that one. It was the end of the day and time to head home. I don't always know for sure if the picture is blurry until i look at it at home on the monitor.

Anyway, I think the joint came out acceptably, and will draw up possibly even more when the wedges are driven in later on. The above picture is taken without a clamp on the joint.

And with that connection done enough for the moment, that leaves me seven more of the same to do. The fitting of those pieces should go a bit faster than the first pair through as I am now confident that the paring jigs are  accurate, and I have a better sense how much material has to come off the spear points on the front rail pieces to get them in the ballpark of a fit.

I'll see if I can take some non-blurred closed ups tomorrow as I work my way through them. Hopefully tomorrow will see me through that.

That's all for now, thanks for reading this far, and hope you are enjoying the series. On to post 39

Friday, February 26, 2016

A Ming-Inspired Cabinet (37)

Work continues on the lower portion of the cabinet carcase framing, an 'ice cube tray'-like structure of interconnected horizontal and vertical dividers. Here are the 24 drawer runner supports, completely cut out save for a final chamfering:

Q-q-q-quartersawn, baby!

The other end of the same supports are dovetailed:

My match marks might be a little on the quirky side.

Later on, after milling the dadoes, I had a chance to check the fit of one of the drawer runners to one of the main vertical support boards:

This is just what I wanted at this stage - a close 'light interference' fit which can be eased very slightly later on. Just a shaving away, that sort of thing.

The horizontals - the rails-  are pretty much complete:

Another view - the spear point miter remain long at this stage:

The spear points are about 1/16" (1.5mm) long at this point. Fitting spear point miter joints requires a cautious approach I have found. You can creep up on your lines, cut by cut, but things can take a bad turn if you go beyond those lines. It's the sort of work I now find suited to aid with an Optivisor, put it that way.

Another view:

Test fitting the rear rails to the vertical dividers, the connections involve pairs of simple half lap joints:

A little closer look:

This joint is about halfway from the fully closed position, and seems to be going together without undue complaint. There is very little 'crushability' with bubinga.

A view from the other side shows the open mortise on the rail to accept the runner support piece's tenon:

The other set:

I know from measuring the parts that these joints for the rear rails should close right up, and they're feeling about right so far, so no point smacking them all the way down with the mallet just yet.

The wider boards which serve as vertical dividers will need some further mortising yet, however they are getting there. The bottom of these boards will have multiple tenons, while the top end will feature a stepped arrangement of sliding dovetails.

All for today- have yourself the best possible weekend! On top post 38.

Tuesday, February 23, 2016

A Ming-Inspired Cabinet (36)

Over the past weekend my wife and I took the opportunity to make another trip down to Springfield MA and visit a museum there. They had a new exhibit on featuring curios and curio cabinets, which included a small selection of tansu. That exhibit was a bit underwhelming however there were lots of neat things to look at besides in other sections of the museum. One of those was a Japanese samurai armor cabinet:

While I had noticed this piece in the past, this time I was struck by the fact that it had bifold doors, like my cabinet design. Bifold doors are not terribly common in Japanese or Chinese furniture, but they do exist. This particular cabinet is larger than most others I have seen-  not that it is an especially common form of cabinet in the first place.

On my design of cabinet, I am doing an unconventional form of frame and panel assembly for the door leaves. This method makes the doors a bit thicker overall than normal; otherwise I am concealing the frames behind the panels. With tall skinny doors, a conventional frame and panel has a slight drawback in the amount of room, visually, that the frames must take up at a minimum. The part often to be emphasized is after all the panel itself, a design direction which tends to push the frame members to be as slender a section as is practical -and as may be accommodated with suitably strong joinery. With the frame members becoming increasingly slender so as to make the panel more prominent, the risk increases that the frame corner joins, typically glued, will eventually give slightly, causing the door leaf to distort. This effect will be more pronounced with a bifold door. Make the frame thicker to afford stronger connections and the view of the panels shrinks commensurately.

Such distortion from shear has occurred with this cabinet's door corner joints at the museum - the inner leafs have sagged relative to the outer ones:

This situation could be ameliorated significantly if several battens were affixed to the rear of the panel to keep it flat, and those battens are then also tenoned into the frame. I strongly suspect that the doors in the above pictured cabinet do not have battens on the backside, at least not ones which are mechanically connected to both the panel and frame. Some people consider the main reason to employ dovetailed battens is for keeping the panels flat over time, which they certainly do, however the other function is to greatly stiffen up the entire door assembly against shear loads as are imposed by gravity. If you only consider the first function, then on a slender door one might conclude that battens are unnecessary since the panels are quite narrow. This is a mistake I think.

These bifold doors are hinged on the front and side surfaces, which means the doors can only open 180˚ and if the door is bumped when in the fully open position then the hinges take a lot of strain from the leverage. This view from the side also reveals no evidence of through mortises for any door battens, as you would typically see on a classic Chinese cabinet:

With a thin frame, through mortises are going to give the maximum strength at the connections, as compared to blind tenons.

The cumulative sag in the door frame assemblies is quite clear to see in this view of the lower portion:

Also, the type of front door latch does little to keep the doors themselves flat and tight to the surrounding casework. Below the doors are a pair of drawers with frame and panel fronts. I am thinking it likely that my glue-less drawer design could also be employed with frame and panel drawer fronts, and that is something I will explore with a drawing when I get a chance.

The door panels themselves did not have the cleanest surfaces:

This view shows one of the blemishes a bit more clearly:

Not sure if that blemish - well, let's call it what it is, a crater - or the many other ones to be found in the panels, occurred after manufacture or during. It's part of the story of the piece.

Anyway, it was educational to look at that 100-year old cabinet, as it confirmed some design-related suppositions I have had in recent months, and I now feel confident that I am on the right track with my bifold door design. Time will tell.

Back at the shop....

Currently working on the joinery for the drawer horizontal dividers, here processing the sliding dovetail mortises for the drawer runners:

Obviously, these are not 'typical' framing joints for web frames, but rather a result of problem solving when one desires to avoid the use of glue.

One by one, you get 'em done:

Another view shows the tongue and groove portions of these two-direction rod joints, nihō sao shachi sen tsugi:

A version of this joint is detailed in tAJCD Volume III.

This joint slides together as follows:

Another view:

The drawer runner stock lay below.

Each of these sticks is actually composed of three members:

A side view reveals the connections:

The sword tip miters remain to be cut so the joint cannot fully close up as of yet.

Another view:

Another view:

When the joints are drawn up, the spaces now seen at the end of the tenons will be considerably smaller, but not zero.

From the back a portion of one of the internal tongue and grooves can be seen:

The tongue and groove forms an enhancement to this connection, a change I made for some good reasons.

Dry fitted, these connections were plenty rigid and tight enough that I could super-surface the assemblies, which saved timer and made all the surfaces co-planar:

The super surfacing removed all traces of tear out from the VG bubinga, not an easy wood to wrangle.

Also worked today were the horizontal drawer dividers used on the back side of the cabinets:

These, as you can see, are one-piece assemblies rather than three-piece. The connections used to attach these to the vertical dividers are simple half laps:

All the drawer runners, 24 pieces, have been dimensioned with high precision and will have their joinery completed next time I'm back to the shop. Then it will be on to the drawer vertical dividers, which have been planed close to finish thickness. Things are rolling along.

All for today, thanks for dropping by the Carpentry Way. On to post 37