Friday, February 19, 2010

Table Making- Shape and Profile

I started the day by laying out the lines for the table arcs on the bottom of the top. I will be jigsawing to the line, and the jigsaw is a coarse tool that tears out to the top of the cut. I layout on the bottom so the tearout will be removed when I rout the profile on the under edge.

I could pattern rout the arcs clean, but I chose to fair the curve with handtools today. I clamp the table together by the rails, tightly to prevent chipout when I work the endgrain across the division between the halves. I only worry about getting the top edge perfect, the router bits bearing will reference off this edge. Hollows left by the jigsaw blades flexing will be removed while profiling.

The leaves are now too long.

I work them to length one at a time, using the finished table proper as a guide.

I begin by scoring the leaves with a chisel, to prevent blowout.

I then clamp a plywood straight edge as a guide for a pattern routing bit. I cut as close as I can without touching the finished table edge.

I then use a handplane to trim the leaf to the right length. I work in from both sides to prevent blowout.

After all three leaves are done, I put them into the table and use web clamps to hold it together. I tighten these as much as I can, I want each leaf to support the next to prevent blowout when routing.

I give the bottom edge a 1" radius roundover. I climbcut when working against the grain to prevent damage, the chalk arrows show my feed direction. I make three passes.

I prefer a variable speed router when pushing big bits. They vibrate too much at full tilt.

I did have a little grain tearout.

To repair it I sand it until the void is full of dust, then apply cyanoacrylate glue.

While it is wet, I sand it more, packing dust into the wet fill.

CA is great stuff, but you must not let it sit too long on a surface, as it will prevent finish penetration.

I then sand the routed edge with a orbital sander at 120 untill the machine marks are gone. I then sand with 150, 180, and 220 by hand, backed by a worn out sanding sponge. I then use a random orbit with 120 to clean up the scratches on the bottom surface around the perimeter left by the hand block and the router.

I now turn my attention back to the skirts. The clients didn't like my initial design, they favoured this one instead.

I began by cutting a lip on the bottom edge of my milled skirt stock.

I then mill a poplar scrap as it's mate.

To make a jig to tablesaw the cove, I used a scrap piece of 3/4" plywood. I screwed a front and back fence to the base, keeping the screws well countersunk and away from the blade area.

I clamped the jig very tightly to the tablesaw perpendicular to the blade.

I raised the blade until 1/16" protruded above the jig base, then slowly passed the stock betweeen the fences.

I repeated this process several times, raising the blade no more than 1/8" at a time, until the cove was at full depth. For safety I clamped a scrap behind the fence to cover the emerging blade. I used a push stick, but only applied pressure over the rear edge where it was supported. I let the dust pile up, eventually it plugged its own holes and was carried down into the saw where it was sucked up by the dust collector.

I make at least two passes over the blade at its final height. This ensures I have a consistent cove, and it reduced the number of deep scratches that need to be removed. Tablesawn coves are difficult to sand clean, I'll use a gooseneck scraper. From what I understand, tablesaw moulding heads leave a nicer finish in fewer passes.

Wednesday, February 17, 2010

Table Making- Top Sizing

I pulled the top out of the clamps this morning and got to work flattening and sizing it. I scraped the glue off the bottom and ran it through the thickness sander, first at 80 then 120 grit.

I sand until the rough faces are gone. By not completely facing the lumber before, and by being painstaking with flatness during glueup, I'm able to harvest a thick top from the 6/4 lumber.

My goal is to have a top no more than 1/4" less in thickness than my rough stock. If I don't make it, I start over.

The widebelt is a great machine, but it does leave snipe. I use the stroke sander with a 120 belt to take care of that. The snipe is obvious after the first strokes of the platen.

From there I joint an edge. The halves get jointed on the middle edge, the leaves on the best edge.

The tablesaw rips to width, 11 3/8" for leaves, 30" for the table halves. The leaves worst edge gets removed.

The leaves best end are trimmed on the sled.

I use a square to clamp on a tool guide to reference the halves against the fence. They're too wide for my crosscut sled. I trim the best end square.

My tablesaw insert has been going strong for a long time, but now the kerf is far too wide and slim offcuts are falling into it. I flip it over, raise my blade through it, and continue on trimming my parts to final length. I set my fence to finished length, 45", and cut all my parts, including the leaves. I don't recommend this technique, the risk of kickback is very high.

I now layout the dimensioned top, label my favourite orientation, and mark for pins and holes.

A pin and hole jig can be made like this.

Remember to register against the bottom for all parts, and against the same end.

I use a dedicated table, registering off centering marks.

I prefer to keep my pins in the lower half of the edge. I think it looks better, and you'll get more refinishes in before you infringe on the holes. I goofed here, and had the leaf in the pin table upside down. The result is a row of holes in the wrong spot.

I used a Veritas Snug Plug cutter to make plugs from the offcut.

These were glued in place and trimmed with a flush cut saw.

I finished drilling the holes. Then I planed away the machine marks, broke the edges, and installed the pins.

I now take the halves and install the rails. I start by closing the rail completely and drawing a centre line.

My tables store two leaves between the rails. I measure 12 1/2" from the centre mark, and use a square to keep the rail perpendicular to the edge.

I'm careful to keep the rail centre line 1/8" inside the table edge. I want the table to close before the rails do.

I screw both rails to one half. Then I clamp the halves together and screw the rails to the second half.

I then flip the table over, clamp it closed, and layout my edge arcs.

That's where I leave it for the day. Tomorrow I'll shape and profile the edges.

Tuesday, February 16, 2010

Table Making- Top Glueup

The layout has been examined by my clients, so it's time to move ahead with the glueup.

I start with one of the table halves. I place the entire half in the clamps, but only glue one joint.

I glue only one joint at a time. This makes it easy to maintain perfect alignment. Any slippage means table thickness lost. I put the entire half in the clamps at once, it's easier to keep track of parts this way, and avoids fibre crushing from the clamps at every joint.

I then glue and clamp the second half.

Then the same with the first leaf.

By now the first joint has firmed up enough to maintain it's bond, so I unclamp it, glue the second joint, and then re-clamp it.

Now I add the second leaf into the routine.

I repeat the process until the entire table is glued up.

My goal is achieved, a dead-flat glue up.

I'm lucky to have access to a clamp rack. If I was using pipe or bar clamps I would alternate their postions, one on top, the next one below, to control cupping.

I give my hands a break, I've opened and closed the clamps almost 100 times, then I fill small flaws. Doing this while the table is in clamps gives the fill time to dry, and it is leveled while I flatten the table.

I start by using an awl to remove punky wood or pith, being careful to maintain the natural edge of the void. I also circle the hole to make it easy to find while I fill.

Conventional wood filler is a shoddy product that has no place in my shop. Instead I colour two part epoxy with universal tints, black for Cherry to imitate pitch pockets, brown for everything else. A little tint goes a long way, and too much inhibits the epoxys cure, so I gradually add it untill I get the shade I'm looking for. I keep mixing to a minimum to avoid air bubbles, and I flow the epoxy into the hole to avoid air pockets.

Dried glue is hard on sanding belts, so squeeze out must be removed. I've had glue pull up chips after it's dried, so I scrape off the top while it's still soft.

If there's a rush for the clamp rack I'll pull the parts out after an hour, but I like to leave them in for as long as I can. I won't work the surface for at least 24 hours. The joints have absorbed moisture from the glue, and have swollen a minute amount. If I worked it now, the top would be flat, but the moisture would leave the joints and they would shrink. These collapsed glue joints would show up as lines after finishing and be unsightly.

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I'm a woodworker on the Canadian prairie.