Friday, October 31, 2014

A Square Deal (34)

Post 34 in a continuing series describing the design and construction of a pair of living room tables in bubinga.

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Have the distinct feeling of rounding the last turn and heading into the straightaway with the side table at least. The last couple of days have been largely occupied with fabricating the double hammerhead keys for the corner joints on the table top, where they serve to lock the breadboard ends in place while allowing the slab top to move with seasonal changes in humidity.

I chose Gabon ebony for the keys. I know it is not the most PC choice out there, but I wanted a wood which was black, somewhat slippery, and extremely hard - it's the perfect choice. It's also extremely expensive these days, and though not as irreplaceable as the table top slab, gave be reason to be fairly cautious in my work. not that I am normally running roughshod over the work mind you.

The keys were rough cut several weeks back. Here they are after being brought to finish dimension and cut to length (slightly over length actually):


I made five keys as it gave me a little bit of breathing room in the cut out sequence.

After one day of work I had cut three of the four keys, and today's work saw me through completion of the 4th key and the fitting of the keys to each corner. I was extremely pleased the way there came together. I'd venture to say I was elated as I assembled the joints and saw that they had come out well. Not every day in the shop is like that - it was a fine day.

So let's take a look at the four corners, starting with #1:


The short end of the key is long by about 1/16" at this point. I can see in the photo a little space above the hammerhead on the left, however I have yet to plane the breadboard edge surface down and I suspect a good portion of that will come out in the wash. I think the entry points on some of the mortises were left a tiny bit rough by the cutter, so by removing material from the face the fit will hopefully tighten up a little bit.

Number 2:


Detail:


The other end:


Number 3:


Detail:


Other end:


And number 4:


Detail:


Again, a little space there above the hammerhead on one side, but I can live with it, considering the difficulty in fitting these up. I feel like I'm showing the world my underwear in pics like these! Nothing to hide here folks.

Another detail:


I was so glad to get through this stage with success. The fits were mechanically excellent all around, with just the two small gaps above two of the keys in just those two spots shown. I may aim for perfection but I never get it - and that's okay. It's all about how far you try to reach.

The extra fifth key did get munched in the cut out, so I was glad to have it there for the sacrifice play.

I know some readers are wondering just how these joints work - don't worry, I'll reveal all when we wrap up this build thread.

The rest of the day seemed somewhat anticlimactic after the keys were in place, however I got some useful stuff done. I trimmed the legs to final length, fitted the backstops to the posts for the demountable panels, and shortened the drawer slightly. No pics, so you'll just have to take my word for it :^)

Also did some work on my dust collection system -more on that in an upcoming post - and received some bronze stock for the leveler feet along with this book:


Some reading ahead. I've been emailing the esteemed Ford Hallam and plying him with questions about wrought iron patination as well.

All for now - have a happy Halloween, if you celebrate it.

Wednesday, October 29, 2014

A Square Deal (33)

Post 33 in an ongoing series.

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Today's task was to deal with the double hammerhead keys which lock the ends of the breadboard ends to the table slab:


There are two main aspects to the task: mortising the slab and breadboard ends, and making the ebony keys. My goal for today was to complete the mortising.

While these hammerhead joints are somewhat novel perhaps, they are 'just' another joint, a series of cut out tasks to be completed. However, what made the work anything but usual was the realization that the parts were not exactly easy to replace should something go wrong. I mean that particularly in reference to the table slab, which started out as a 3" thick chunk of vertical grain bubinga.  I don't know of any other 3" thick slabs of bubinga on the market at the moment, or any coming along anytime soon, let along a perfect vertical grain piece. And in any case, if such a piece could be found it would likely be far more material than I actually needed and I'd be looking at several thousand dollars. They don't just sell 24" squares of 3" thick bubinga. So, it was most definitely the case that I did not want anything to go awry in the joint cutting on the table slab. Uh-uh, nope. No way.

Adding to the 'irreplaceable' aspect to the slab was the fact that I already had many hours into the fabrication of the top and breadboard ends. Every visit for marking out and cutting is an opportunity to screw something up. And added to that, I would be cutting the joints in a hard wood with a somewhat slender and long router bit at max. extension- I was apprehensive about the chance it might flex slightly, catch and possibly break, possibly ruining something wooden.

So, while not feeling abject terror perhaps, I was a little stressed out and took on the task today with great deliberation and care. Hyper-focus even. Some of the cutting was a mix of routing and chiseling work, back and forth, until the joints were cut. In the end, everything came out well. Whew! The bit did its job without breaking, and the joints are to dimension. I found camellia oil helpful as a cutting lubricant.

Here's one corner, with the breadboard end re-attached:


 Another view of the same corner:


A different corner:


The crosswise mortises are for some 1/4" (6.35mm) pins which will be wedged at each end to tie the works together.

Another view - not the best picture:


Corner 3:


Corner 4:


I also mortised the central part of the breadboard ends for their connections to the middle tenons on the table slab:


All for today. Tomorrow will be key, if you know what I mean. I'll try not to get too keyed up about it I guess. :^)

If it is of interest: post 34

Tuesday, October 28, 2014

A Square Deal (32)

A new installment in a continuing series. Recent posts can be found in the 'Blg Archive' section to the right site of the page.

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Demountable Panel, Continued....

As mentioned in the previous post in this thread, after making a frame and panel version of the demountable rear panel assembly, I decided that a different form of construction might be better. After remaking the part as a 'slab' with double-mitered breadboard ends, I realized a few further refinements could be made so I elected to make it for the third time.

This one came out as planned - here, I'm dressing the top edge to fit the opening:


Trial fitted in the opening:


Right side:


Left:


The rear inner corners had some material removed to fit around the rear of the drawer stops:


Another view:


The breadboard end is fixed with a tongue from end to end and a central through tenon, which will be double wedged later on.

With the panel more or less where it needed to be, I could make the mechanisms to hold the panel in place. These start with two tiny mortises in each breadboard end:


A view from the other side shows the housings to accommodate the clips:


This picture shows two clips after fitting - one started, and one fully inserted:


Then I had to make two more tiny mortises in each leg to receive the clips:


Mortising done, I could refit the panel and make sure the clips engaged as they should:


Left side:


Right:


I believe I will shave another hundredth of an inch out of the jogged up section of the panel's lower surface to achieve a slightly better fit yet of the panel to the surrounding framing. Right now the panel is a just a skoosh tight in the opening, leaving me a final shave with the plane.

'Skoosh' - there's one of the few words in the English language which is borrowed from Japanese and doesn't relate to food or combat arts. The Japanese loan word is 'sukoshi', BTW.

A view from the inside shows the panel fitting around the drawer stop:


The other side:


This panel is thicker than the previous (and initial design) so it overlaps the stretcher slightly on the inside face on the interior of the cabinet - hence the shadow line visible in the above two shots. The panel's lower outside arris will be chamfered yet, and I'm not too bothered about it, but it would have been a little better to have the panel and stretcher meet flush. This detail is on the inside of the cabinet after all, completely unseen, but it is little details like this I can chalk up to 'lessons learned'.

One of the main reasons I'm putting this drawer and demountable panel system in this small side table is it is a dry run for larger and more complex constructions, like the sideboard I spent a bit of time designing last year. It's a prototype of sorts in respect to the drawer construction system - a 'proof of concept' if you like. So it is not surprising that little details like this overlap become apparent upon construction. It would have been better if I had redrawn the rear panel in my CAD program before fabricating and I hopefully would have caught the detail there. I could choose to remove some material from the back of the panel, but I hardly think it is worth the bother.

I will be fitting a couple of pieces down the inside face of the legs to serve as backstops for the demountable panel, so that it won't be depending solely upon the clips to keep position.

A view of the drawer placed in the cabinet, relative to the rear demountable panel:


And a last one showing the view from the demountable panel side:


The interface between the clips and their housings will be eased so as to make them more obvious and to allow a tool, like a small thin screwdriver, to enter and prise the clips out.

Let's see, that leaves me with just a few details to take care of now. Next will be the ebony double hammerhead keys to be fitted to the table top corners, some work on the side panels and chamfering of various parts, and the fabrication and fitting of the bronze leveler feet and drawer pull knob. And then finishing. Then it will be time to repeat much of the process with the coffee table build. So a few more posts to come yet in this series -  hope you're not getting lost in the details!

That's for your visit to the Carpentry Way. Another post awaits: 33

Sunday, October 26, 2014

A Square Deal (31)

A series of posts describing the design and construction of a pair of tables in bubinga.

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Demountable Rear Panel.

I chose to make the rear panel on the side table demountable - meaning readily taken on and off - instead of fixed, as in a standard floating panel trapped in the surrounding framing. My reasoning was that service, adjustment and repair of the drawer 'mechanism' would be far easier if you could access both ends of the cabinet. Working into a narrow dead end space from the front, as would be the case if the rear cabinet panel was not removable, is more of a hassle, more awkward, and makes a good result less likely. While it adds a certain amount of complexity and fabrication time to have a demountable panel instead of the more usual floating panel trapped in a frame, I think the benefit is worth it, even if the benefit will likely accrue to someone working on the cabinet long after I am gone from the world.

My initial concept for the demountable panel was to build a frame and panel unit which would nest inside the existing framing somewhat discretely. Here's the look of the panel when installed:


The frame of this demountable unit looks better the smaller it is, it seems to me. If it were much taller in section, the panel within becomes rather obscured. I settled on a section height of 0.5" (12.7mm), and a frame width of 13/16" (0.8125", 20.63mm). The panel was to be around 1/4" (6.35mm) thick.

A problem with such a thin frame however is that over an extended time, the upper horizontal member could possibly sag a little bit. It couldn't sag too far as the panel would support it, but it could definitely sag enough to make a gap to the framing above.  A solution to this, I felt, was to make the frame step down, so that the frame section was an inch tall behind the panel, stepping down to 1/2" for the front reveal.That would add a little challenge to the corner connections, but nothing too onerous.

So I started fabricating the parts yesterday. I got most of the way along, just shy of profiling the lower rail and fitting the parts up:


The corners of the frame, after the dado is cut to accept the panel, doesn't leave much room for a joint. The only decent solution I felt was a form of staggered finger joint:


A finger joint would have to be glued of course, and that's where I started having second thoughts.  I've done this form of construction many times in the past, and there's nothing really wrong with it - - but I'd prefer to avoid glued construction if I can do so. Maybe the issue lays in the design of the demountable panel?

So I put that above parts to one side, and started over again. In reconsidering the visual I wanted to achieve, I realized there was another way to make the part, just as a slab table with breadboard ends is an alternative to a frame and panel table top. Why not make the demountable panel in the same manner?

That seemed like a reasonable way to proceed, so I went to the shop today for a spell to see what sort of trouble I could get into. The result of an afternoon's stumbling around:


Another view:


So, success? Well, not quite. I think this means of building the rear panel will be the ticket, however there are a few details which arose that didn't quite suit me, so I'll make it again. Third time's the charm? I'm getting a damn good amount of practice!

This may seem like a lot of fussing for a panel at the back of the cabinet that no one ever sees or thinks about, but I know it's there and I know how it is made. And how it is made matters to me greatly. This piece has to meet my own standards for construction and won't leave the shop until it does. I mean that in every respect, down to the last detail.

Are you ready for the next installment? Post 32.

Thanks for coming by the Carpentry Way.

Friday, October 24, 2014

A Square Deal (30)

3-0 reached in the post count for this two-table build. Getting there, I think, with the side table....

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A few pics to share today. I spent the first while at the shop this morning completing the housed multiple mortise and tenon joinery between the drawer front and sides, and drawer rear wall and sides. Once the parts had been (dry-) fitted up, it was time to see how it all assembled.

This is the basic configuration of parts prior to assembly -the rear wall is joined to the sides, and the runners are mounted on the floor pan:


The sides then slide onto the runners along their hammerhead sliding tenons:


The sides and rear panel assembly now more or less slid all the way to the front:


Now the front panel can be fitted, these are housed multiple mortise and tenon:


Almost home as the front tongue on the floor pan engages the dado on the inside face of the front panel:


Done:


A closer look at the through tenons on the front- the mortises are yet to be flared for the wedges which will lock the tenons in place:


The join between the rear wall and a side - here I have partially flared the mortise walls just to facilitate fitting up:


These tenons are way long at the moment, however they still clear the surrounding frame without issue, so nothing to deal with immediately.

Under view of the drawer:


 A closer look at the sliding hammerhead connection between side wall and runner:


Another view:


At this point the drawer could be just wedged into place in the cabinet, a bit too tight for sliding operation, but it enabled me to see how the fit of the front panel looked to the surrounding frame members now that the drawer was together:


Another view:


As mentioned in the previous post, I was targeting a 0.01"~0.02" gap between the bottom of the drawer front and top surface of the stretcher, and on the left side I was sitting at 0.016":


In case these decimals are giving you fits, note that 1/64" = 0.015625"

The other side was a hair tighter at 0.015":


So, just around the target clearance I was looking for -seems like it will fly. I'll give the top edge of the drawer rather more room, though with a quartersawn drawer front in this material I would be surprised if more than a 1/32" (0.03125"/0.76mm) clearance would be needed. The sides of the drawer can run clearances of 1/64"-ish each I would imagine.

A look at the back of the drawer nestled in among the wear strips:


The middle of the drawer is fixed to the rear wall using an elongated expansion slot with a wide-head machine screw:


I will extend the slot a bit more yet, but this will do for the moment. This is a fairly standard way of keeping the drawer from sagging in the middle and allowing it to move with seasonal shifts in relative humidity.

A closer look - this fastener is generally used on knock-down furniture - I thought its bronze patina was reasonably close in color to the bubinga and the wide head means no washer is needed and it gives ample support:


A couple more pics of the underside of the drawer just for the heck of it:



I then proceeded to fit the vertical wear strips to the support rails with some countersunk #6-32 stainless Allen head screws:


The drawer fit is still a little on the tight side, however I'll leave final fitting and adjustment of the drawer until after the cabinet is assembled and all the pegs are knocked in.

One more detail to be fitted were the drawer stops. I forgot about these altogether yesterday when I mounted the horizontal wear strips, however the screw location was exactly the same so no big deal. In the above picture you can just see the shallow dado that has been cut in the end section of the horizontal wear strip, and below, the wooden stop is placed into that dado, the stop itself having a shallow tongue on the underside:


These are fastened by 1/4"-20 stainless button head cap screws, also Allen head:


I detest Phillips head and slotted screws, and would have ideally placed stainless Torx screws, but they are not so readily available so I went with Allen head instead.

The screw slot in the stop is elongated to allow for up to 1/8" of fore-aft adjustment:


One more look:


The idea is that with the rear panel removed, it would be easy to make adjustments to the fit and placement of the drawer, including the stops.

It was good to end the week by bringing the drawer to a close, so to speak. That leaves just one more piece of construction on this side table, namely the demountable frame and panel assembly which fits to the rear of the piece. I'll be at the shop tomorrow working on it so we'll see how far along we get.

Thanks for visiting the Carpentry Way. I guess it might be time to make a move to post 31 now, hmm?