October 17, 2013

A bookshelf for Little Man

Back in July Laura mentioned that she was looking for a bookshelf for the nursery we were preparing for Little Man, our loving code name for the child we are expecting later this fall. As a woodworker I took her suggestion that we buy one as an insult and immediately offered to build one instead. Based on the typical pace of my projects Laura was concerned that this bookshelf might end up dragging out until Little Man's first birthday, but she reluctantly agreed under the condition that it was done by the end of September. I figured a bookshelf should be doable in 2 months...

Challenge accepted.

I had initially hoped to use lumber from my stockpile but the looming deadline had me looking to keep this as simple as possible so I decided to head over to H&K Woods to see if they had any wide stock so that I could avoid the need to glue-up panels to get the full depth needed. They had a fresh stack of red oak and I was able to grab 5 nice wide boards that were almost perfectly clear.

After looking over the lumber I decided cross cut the nicest board in half for the sides of the shelf and let the length of those pieces set the height (~48"). 

This height would fit 4 shelves with reasonable spacing and dividing an 8' board into thirds set the width of the shelf at roughly 32". This also meant that this load of lumber would yield two of these bookshelves so I'll probably end up building another one for Lex some day.

It was nice to finally put the workbench to use on a real project, starting with flattening one side of each rough piece with a jack plane and a pair of winding sticks.

I then ran the boards through the planer starting with the flat face down on the table to true up both faces and bring the sides and shelves to a consistent thickness of just under one inch.

At this point I started playing around with some whole number ratios to define the locations of the shelves. Through some trial and error I settled on a ratio of 9, 11, 13 for the shelf to shelf spacing and then added in another 5 units for space above the top shelf and 3 units for the space below the bottom. I then set the dividers to step off the overall height into the 41 total units and then made marks at 5, 9, 11, and 13 steps from the top leaving 3 steps below the bottom shelf. This may seem complicated at first but it is very simple in practice and it allowed me to locate the shelves and layout the design without the need for a tape measure or any math (other than counting).

Stepping back into the 21st century I also modeled this design in sketchup as a sanity check and to get a final stamp of approval from the wife. The sketchup model was helpful to visualize the curves whose degrees of curvature were also based on the same whole number proportions as the rest of the shelf. The model also helped me decide how to handle the termination of the back boards at the top of the shelf. I had initially considered some sort of cross piece to cover the end grain of the back boards but ended up leaving them exposed and dressing them up with the curve across the back as shown below.

With the design finalized and the stock milled flat and to thickness I started working on the shelf joinery. I started by cross cutting the sides to final length, plowing a dado for each shelf with the dado stack, and then ripping the sides to final width.

Next I crosscut the shelves to their final length, used the dado stack to cut the full width tenons to fit the dados previously cut in the shelf sides, and then ripped the shelves to final width.

Next I plowed a groove along the inside back edge of each shelf side to capture the back boards.

The next step was to mark out the mortises in the sides for the twin through-tenons with the dividers. Each tenon is one sixth of the width of the side and is located 1 sixth from the edge, with 2 sixths between them. I used the two pieces of scrap shown below to help visualize this layout.

I started the mortises by marking out the locations inside of the dados on the inside of the shelf sides. The sidewalls of the dado set the mortise width and the length were marked out with a knife.

I used the brace and the closest size auger bit to hog out most of the waste, starting from the inside and then finishing from the outside to get nice clean holes.

I transferred the layout lines for the mortises to the outside faces of the shelf sides and then started chopping out the remaining waste inside those lines with a chisel. The final dimensions are set by starting the last fine cut with the chisel placed right in the knife line so that the mortises are all a consistent size.

This process started out fairly slow and could have probably been sped up by using a router and a template, but it was fun chopping these out by hand. After the first few sets it picked up quite a bit.

I did have a few issues where I got careless and ended up splitting off a chunk of the outside face while paring the mortise walls from the inside.

I was lucky that in most cases the split off pieces remained attached so that I could simply glue them back in place.

This particular patch job wasn't perfect but it isn't too obvious on the finished shelf and without this simple repair I wouldn't have had any chance to get this project done on time.

With the mortises cut it was time to set the shelves into the dados and use a knife to mark off the tenons based on the mortises.

To help ensure that the sides of the tenons were sawn exactly in the right spot I used a chisel to cut a small notch at each knife line with the waste side sloped and the side that defines the tenon edge nice and straight. This notch helps locate the saw as you start cutting so that the tenons fit the mortise right off the saw. After sawing the sides of the tenon I marked off the waste areas to make it very clear what parts go and what parts stay.

I ended up cutting out this waste with the band saw, leaving just enough between the tenons to lock the shelf in the dado and prevent any cupping across the grain.

I was also very careful at the bandsaw to leave the little tabs at the front end of each shelf that will fill the exposed ends of the dados. You can see this below at the very far left corner.

In general the tenons fit the mortises right off the saw, but it did take some futzing to trim the front ends to fit just right. Too long and the shelf wouldn't seat fully into the dado and their would be gaps at the shoulders where the shelf meets the side, too short and there would be a gap at the exposed dado at the front of the shelf.  Below you can see a gap between the shoulders and the inside face of the shelf side... this one needs some trimming.


After paring down the end slightly the shoulders are tight and there is no gap at the front of the dado, success.

Once all the joints were fitted I did a dry run assembly to see how things were coming together and to check that all the joints fit together nice and tight all at the same time.

Its always fun the first time a project stands on its own.

The joints looked good so I pulled the assembly apart and started working on the curve at the top of each side. I used the dividers still set to the same distance used to space out the shelves and stepped down one step on each side to define the limits of the curve. I then used a flexible metal ruler and a piece of string to cobble together a makeshift drawing bow and used that to trace out the curve with a pencil.

I cut the curve on one side with the bandsaw and then used that side to mark the curve to be cut out on the other side.

I clamped the sides together and used a spokeshave to remove the saw marks and smooth the curves on both sides at the same time to ensure they were perfect mirror images.

The next step was to resaw some more red oak scraps from my pile and mill it down for the back boards. The boards mate together with a ship-lap joint cut with the dado stack to allow for the seasonal expansion and contraction.

Since these boards won't be very visible once the shelf is full of toys and books this was a good use of some less than perfect stock, a few knots won't hurt anything.

Lex then helped me re-assemble the shelf and mount the back boards so that I could draw out the curve across the top. She tried to run away when I started taking pictures so when I asked her to pose she made a silly face in protest.

I removed the back boards and cut the curve on each piece individually at the bandsaw, then mounted them all back on the shelf for final smoothing.

The spokeshave took care of the saw marks and evened out the curve nicely. I also used the spokeshave to add a small bevel to the top of the boards at each end where they mate with the perpendicular curve at the top of the sides to blend things together.

At this point all of the major tasks are done and I started to tie up a few loose ends and prep for finishing. There was one small chip out around a mortise that I missed earlier so I grabbed a sliver of oak off the floor that was about the right size to make a patch.

I applied a touch of glue and clamped the sliver in place to fill in the defect.

With the glue dry and the patch planed flush it basically disappeared.

One of the last steps before finishing was to hit all the surfaces with a smooth plane....way more fun than sanding and much more effective at removing the tearout that I have come to accept as inevitable when running red oak through the planer.

So far this project was still tracking on schedule but it had been a few weeks since initially flattening the boards and they had cupped slightly with the end of summer humidity changes. This made it tough to get the smooth plane into some of the dips and valleys so I needed to find another way to smooth those spots. I considered just sanding those areas but I was concerned that the different surface texture would take the finish differently than the planed areas and I really didn't want to sand the whole thing. I finally took the time to figure out how to sharpen and use a card scraper and was blown away how well it worked. Again, way more fun than sanding.

In order to ensure that this bookshelf survives just about anything little man would throw at it through his lifetime I may have gone a bit overboard with the joinery. The through tenons on each shelf are wedged from the outside into a flared mortise which is about as bomb-proof of a joint as you can get. I cut two saw kerfs on each tenon to accept the wedges during assembly.

I then marked a knife line to widen the outside of each mortise by just a hair. I then pared down from this line at an angle to intersect about half way into the mortise so that the outside half is flared slightly wider.

I the wedges from a scrap of oak and proceeded with assembly. I applied glue to the mortises and tenons and then assembled the shelf. I used clamps to tighten everything up and then adjusted the clamps to square up the shelves to the sides. I then put just a touch of glue on each wedge and drove them into the saw kerfs as pairs so that they flared the tenons evenly.

After the glue dried I removed the clamps and used a chisel to chop off the majority of the protruding wedges. The fact that the tenons themselves were proud of the side panel offered a bit of insurance in case the wedge broke below the tenon surface slightly. I then switched to a block plane to trim the remaining wedge bits and excess tenon length flush with the side. Most of the joints turned out really well with only a few small gaps on one or two of the joints.

Trimming the wedges and planing the tenons flush left some marks around each joint that needed to be cleaned up with a smoothing plane so I rigged up a few scraps on the bench to hold the shelf on its side. This allowed me to take full length passes with the smoother.

After a few passes the shelf sides, including the exposed end grain of the tenons, was nice and smooth once again. Here you can see the detail of the wedged tenons and the nice tight fit.

I generally prefer a simple clear finish leaving the wood a natural color but in this case Laura had requested something a bit darker. I took this as an opportunity to try out something new and settled on General Finishes Dye Stain (light brown). Dye gives the oak a much more consistent and even color compared to a pigment stain which tends to collect in the open pores and really highlight the grain. The dye stain also has just a bit of binder to lock in the dye which was very helpful in this case as I was planning on a wipe top coat. Without the binder the dye is likely to re-activate while wiping on the top coat creating streaks or dark splotches. After applying the dye and letting it dry I then wiped on 3 coats of a 50/50 polyurethane/mineral spirits blend.

I put on the last coat of finish a day before the deadline Laura had challenged me to and it was a perfect sunny windy day to let the shelf sit outside and off-gas most of the polyurethane stink.

I moved the shelf inside and Laura quickly loaded it up with toys, books, and other baby odds'n'ends.

My hope is that this shelf survives long enough to be handed down to little man's own little man some day.

No comments:

Post a Comment