Saturday, March 28, 2015

Portable Flea Market Display Case, part 4

(Go back to part 3)

An oak "mud foot" adjustable leg leveler.

To make the mud feet, I resawed and planed a length of 3" wide oak. I hollowed out the insides with a series of forstner bits (using a hand-held power drill), then epoxied in the feet of threaded leg levelers.

Once the expoxy had cured, I sawed them off into squares, sawed the corners off and rasped them to round, then applied finish. I attached the threaded sockets to the bottom of each leg.

I attached the locking hinges to the legs and then to the oak baseplates. I screwed in the mud-feet and closed down the hinges. This revealed my next mistake. Can I say how much I hate dealing with hinges?

This was another case of small problems adding up. First, slight alignment issues in the hinge installation meant that the legs bumped into each other instead of laying down flat alongside each other. Second, the sizing of the mud feet and width of the leg assemblies meant they wouldn't fit properly even without the alignment issue.

This was a more significant mistake than the others. Finally, I drew inspiration from my friend Freddy Roman, maker and restorer. He does a lot of repairs of failed joints, particularly on chairs. He doesn't waste a second of hesitation before cutting them off and remaking them.

Similarly, my wife is an orthopedic surgical nurse who does a lot of joint repairs. They go right in, cut off the old failed joint, bone or metal, and make a new one. Orthopedic surgeons probably make great woodworkers!

OK, so just do it. I could cut one side off each leg assembly, excavate the mortises, recut the tenons, touch up the finish, and the narrower assemblies would fit properly, with some margin for hinge alignment.

Ouch! Cutting off a leg stretcher.

The cutoff ready for remaking the joints. The rest of it went fine.

The next step was flocking the interior. I had never used this material before. The brand is DonJer. The instructions said it was easy, regularly used by junior high school students on their projects, and recommended consulting one in case of difficulty. Since I was fresh out of junior high school kids with mine off at college, I was left to flail on my own.

The setup consists of a bag of shredded flocking fibers, a can of glue in matching color, and a cardboard tube pump applicator. The glue is like a heavy paint. The fibers are very light and a bit dusty.

I taped off the finished edges of the case and painted the interior of the right side with the glue. I poured some fibers into the tube and pumped them uniformly across the wet glue. The process was just as easy as advertised.

The only problem was that I was a little light on glue application. The instructions said to spread it thickly with a brush or roller. I used a brush, but didn't use quite enough. This left slightly visible thin streaks in the flocking against the light colored wood.

I went ahead and did the left side. This time I applied glue generously in the naval fashion: if it moves, salute it, if doesn't, paint it. Thickly. The results were much better, a good uniform coating and flocking.

The instructions said to let it dry for 10-15 hours before reclaiming loose fibers, and allow 72 hours to a week for final curing. While I gave it time, I contemplated what to do about the streaks. I thought about trying to do a second coat, but wasn't sure how that would turn out.

In the end I decided to strip it down and redo it. I used a card scraper to remove it. I'm happy to say this was much more difficult than I expected. That glue and flocking are tough stuff. It certainly eased my mind about the surface getting torn up in use.

I still had enough glue and fibers left to do a thorough coating, and the end result was as good as the other side. After the glue has cured, it feels like velvet stretched tight on the wood.

Flocking applied to both side.

The setup: glue, pump applicator, and fibers.

Next step was installing the acrylic panels in the doors. You cut this stuff sort of like glass, scoring it repeatedly with a knife along a straightedge and then snapping it off.

I wasn't thrilled by the knife sold for this purpose, so I ended up using the chip carving knife that I use as a marking knife. I also ran a veneer saw along the straightedge to cut faster.

Probably tool abuse, but a block plane along the snapped-off edge does a great job cleaning it up and paring it down for precise fit. This still has the plastic wrap facing on it to protect against scratches.

Boring screw holes for the backing strips with a birdcase awl. I've already installed the piano hinge to the doors.

With the acrylic in place after pulling off the facing, screwing down the backing strips.

The final step was installing all the hardware. The piano hinge gave me almost as much heartburn as the leg hinges, but I eventually got it.

Rear view showing the handle, door latches, and screw eyes for securing to chains.

Side view showing a brass lid support.

Side view closed up.

Underside view with legs unfolded...

...and folded. The hinges latch in both positions. It does take a bit of coordination to unlock both hinges and move a leg assembly using only two hands.

Front view in folded-up tabletop mode.

This does mean several inches of interior capacity are lost to the legs storage underneath.

While the locking hinges worked well, they had enough mechanical play in them to make the stand rattly. After all this effort I wasn't going to allow that. I made thin oak strips to act as leg braces. One strip on the near side of each assembly, secured with carriage bolts and wing nuts, was sufficient to make it rock solid.

The latch release on a hinge. The hinges are through-bolted to the legs and bottom as well as screwed, to prevent tearing them off if something crashes into the side.

An oak leg brace.

Securing the brace to a leg unit.

The brace secured to leg and case.

Underside view.

This was good starter project. It was big enough to help expose and sort out several issues, yet small enough that the downside was acceptable. Now I know better for future clients!

Portable Flea Market Display Case, part 3

(Go back to part 2)

The next step was assembling the frames with drawbores.

Driving riven pegs through a dowel plate to size them.

Boring through the mortise for the peg.

Spinning the bit backward to mark the hole position in the tenon.

Marking the offset hole position just 1/32" or so closer to the shoulder.

Boring the tenon.

You can just make out the offset crescent of the tenon hole inside the mortise hole. The slight gap of the tenon shoulder will draw up tight once the peg has been driven in.

Driving in a peg.

Glued up and checked for square. Drawboring doesn't allow for much adjustment, so you need to do a good job squaring up the shoulders ahead of time.

Trimming the pegs before final flushing with a chisel.

Cutting the horn off a stile.

Planing the horn endgrain down flush with the adjacent rail edge.

Planing the joint face down flush.

The frames resting on the case.

This was where I realized my first construction mistake. I had sized the rails and stiles exactly before joining them, so that the widths and lengths all added up to the total case width, carefully squaring them up.

However, small errors in squareness conspired against me. The case was about 1/16" out of square to the left. The frames were about 1/16" out of square to the right. So they were two opposing parallelograms. Put together, the result was 1/8" out of square. After all that care, that would be too much of an error. Any adjustment in positioning just made it worse.

The problem was that I had sized everything to theoretical shapes, not to the actual shapes present. Had I left the rails a little wide, I could have trimmed them down exactly to match the case. But since I had already taken them down, there was no material left to do this. Lesson learned: leave the outer edge of the frame oversize, then plane down to the exact case shape.

To fix this, I glued narrow strips to the outside rail edges. Yes, I put wood back! Once it was dry, I flushed the strips down to the rail faces, then planed them down to exactly match the case as I should have done originally.

The next step was making the leg assemblies. These were essentially frames like the doors, with drawbored mortise and tenon joints.

The first leg unit after driving the drawbore pegs.

Closeup of a corner drawn up tight.

Completed legs after trimming and flushing the pegs.

Now I realized my next mistake. I wanted to have a small oak baseplate on each side underneath to attach the leg hinges. The plywood bottom was not sufficient to hold the screws. I had intended to house them in a partial groove in the sides along with the plywood. However, I had forgotten to do that when I glued up the case.

My solution was to add a stopped groove to the inside front and back after the fact. Instead of a full groove in the side, since I was using oak, I formed wide tenons to accept long grain tenons.

The next question is, how do you fit a piece wider than the inside dimension of the bottom into the stopped grooves? Answer: sliding wedges. You know, the magical stretching board!

I cut each baseplate on a long diagonal and carefully planed the cut edges so they would form a good edge joint. The diagonal meant that this was mostly a long-grain joint, so should glue up good and strong. That way I could fit one wedge in place, then slide the other one into place with glue applied.

Chiseling out the stopped groove in the back piece on the underside of the case. Yeah, this is as awkward as it looks.

An oak baseplate cut diagonally. You can see the long-grain tenons and matching mortise slots on the left. The upper end slides into the stopped groove. The opposing wedge slides into the matching stopped groove at the lower end.

With the upper wedge in place, the lower wedge loosely in place to show how it will slide in. With glue and clamps, that diagonal seam closes up invisibly.

From there, a variety of small detail steps.

Planing the top back edge to match the slope with a block plane.

Planing down the thin backer strips for holding the acrylic in the door frames.

Pre-drilling the screw holes in the strips.

With stain and two coats of satin polyurethane spar varnish applied, everything carefully stacked in place before installing any hardware. The clamps act as feet to hold the legs straight up.

(Continue to part 4)

Portable Flea Market Display Case, part 2

(Go back to part 1)

Before assembling the case, the next steps were grooving it all around for the plywood bottom sheet, and fitting the center divider with sliding dovetails. You can see the detailed procedure for making a sliding dovetail on this page.

This was an important joint, because I wanted the divider to hold the back stiff when the case was carried hanging by the handle in back. A simple dado would not provide any mechanical support, the back would pull away from the divider.

Sharpening the 1/4" iron for my plow plane, using a DMT coarse diamond plate, 1,000 and 10,000 grit Ohishi ceramic waterstones, and a strop.

Plowing out the groove.

The front and back grooves are stopped, so the skate on the plow plane prevents reaching all the way to the end. Using the plow iron as a chisel to plow out the last couple inches.

Crosscutting the walls of the sliding dovetail, stopped at the groove.

Chiseling out the bulk of the waste.

Precisely leveling the floor with a small router plane.

The completed dovetail socket.

Using an angled guide piece to precisely pare the dovetail tongue.

The completed tongue.

Sliding the divider into the back.

Cutting the plywood bottom to size. Handsaws work just fine on plywood. The thin cross grain veneer layers are just a bit more finicky to deal with than solid wood.

Shooting the plywood edge straight and square. Handplanes also work just fine on plywood.

The glued up case.

The next step was making the door frames, using drawbored mortise and tenon joints. For details on how to make the basic mortise and tenon, see this page.

Drawboring is amazing. The resulting joint feels as solid and strong as if the wood had grown that way, like the branch attached to the tree.

Rather than a groove, the frames had a double rabbet to hold the clear acrylic. This was then held in place with thin oak backer strips screwed in. Should an acrylic piece need replacement, the backer strips can be unscrewed to remove it.

Ripping the frame rails and stiles.

The first frame dry fit, with horns still on, and all the tools required.

The stepped rabbet on the back of the frame.

Closeup of one of the joints.

Closeup of mortising the second frame.

Chopping a mortise.

Sawing the corners of a tenon cheek.

Sawing off the remaining tenon cheek waste.

First step forming the rabbet, the big fast tool is the moving fillister plane.

The second rabbet is stopped. Using a bull-nose shoulder plane to get up close to the end.

Using a better shoulder plane for the bulk of the rabbet.

Where I have room, using a wooden skew rabbet for fast stock removal.

With the bull-nose removed, using the shoulder plane as a chisel plane to get right up into the corner.

(Continue to part 3)