Framing, project R.E.

[workin for wood]

I still have a ways to go on the intarsia portion of my project, but the frame also needs to be started. The first part of the frame is a 16" diamater circle. This will be built in two parts, for two reasons. It is a segmented circle, which requires quite a bit of lumber; much more than one would think. A 16" circle requires a board almost 6' long. The circle is curly mahogany santos, which is pretty expensive. A second circle is required to give the first circle structural strength. Also the second circle adds the appropriate thickness. The second circle is maple, to save on lumber cost, and it will only be visible from the back in the end anyhow. The back of a picture is important, it must be clean, but does not have to match the front. Segmented circles must be built end grain to end grain for stability purposes. End grain joints are not strong, but when doubled up and over lapped, they are solid as can be. So the top circle will be glued on to the bottom circle with the joints staggered. Just regular wood glue is strong enough to hold the circles together as they are passed through the sander to clean them up before gluing. Clamping does not have to be done if you rub the wood together with lots of glue, creating a suction fit.
Lumber must be straight and true before cutting. A stop block is used and the board is simply flipped after each cut. Once all the pieces are cut, all burrs are removed. This is so important. Any piece of sawdust will make the pieces not join together properly, this goes for dried glue nerdlies on your glue bottle too, so remove those. The pieces are all dry fit together as a test, and then glued.

Why bother doing this prep now instead of when it's needed?

When gluing wood, moisture is introduced into the fibers which creates swelling. The joints are swelled up. The idea is to glue the pieces together and then let them sit for a few weeks to guarantee they are completely dry and un-swelled before sanding. It may look and feel dry the next day, but the swelling still exists. If you sand, you will think you have a nice flat board. A few weeks later, there will be a small dip where the wood seems together, and that doesn't look good. This isn't just for end grain glue ups, it is the same for all glue ups. Some woods swell more than others of course, but all woods do swell. Think back to any glued up panels you may have hurried through in the past, now go feel where the joints are today. Chances are, you will feel the joints. The eyes and the fingers especially, don't lie.

How to calculate your circle.

A circle is 360 degrees

The circumference is equal to it's diameter times pi

pi is 3.1416

Diameter of a circle is equal to it's circumference divided by pi

Circumference divided by how many segments you choose to use is the length of the segment. Length is considered to be the outside edge of the segment piece.

The angle is simply 360 divided by the number of segments and then divided in half again. For example. 20 segments at 18 degrees equals 360. But 18 is not the angle, 9 is the angle, half of 18. This is because you have half the angle on one segment and the segment that joins it carries the other half of the angle. So the two pieces when they join become 18.

[workin for wood]

I do have a circle jig for my router, but it is too large for a circle of this size and I do not want to drill holes in it. You may not have a circle jig anyhow, so this is a good thing. It's best to build the jig with solid wood, not plywood. Thickness should be 1/4 to 3/8 thick. The plate on the router is removed. It is traced onto the wood that will become the jig. Trace the outside, inside and the screw holes. Measure down the board, for this jig, 14" is plenty long and mark that spot. Measure to the center and draw a line so the end of the jig becomes a 1" square off rather than becoming a sharp point. Draw a line from each side of the 1" to the side of the circle so you basically have a long rounded triangle. Cut out the jig with the scroll saw. Drill out the holes. Countersink the holes and install jig on to router. This is a very simple jig to build, shouldn't take but 5 minutes.

[workin for wood]

The circle is cut mounted on a scrap of MDF. First a square is drawn on the MDF, the square is approximately the size of the circle. The corners of the square are connected to reveal the center. A long bolt and nut is found. A hole is drilled into the center of the square using a bit the same size as your bolt. A piece of wood that is the same thickness as the circle is drilled with same bit. It is glued into place using the bolt as a clamp which also lines the two holes together.
The circle is set into the square. It is measured a multitude of times from the center to line it up into the proper location. It need not be 100% centered, but needs be darn close to it. Each pie section on the MDF is given a letter of identification. The Circle is traced up and across, which turns the circle into 4 quarters. The same letter assignment is written on the circle. Now the circle can be removed and replaced to the exact same location. The circle is screwed from the bottom to the MDF. The screws are located under the line that quarters the circle, and halfway between the width of the circle. You don't want the screws too long or anywhere near where a router will hit them.
A 1/4" straight flute plunge cutter bit is installed into the router.
Measure from the center of the bolt to the outer edge of the circle. Deduct a half inch from the measurement. Now measure from the bit toward the tip of the circle jig and mark that spot. This is where you drill your hole to mount the jig to the bolt. How wide is your frame/circle? Lets say it's 2 inches. From the center of the bolt hole in the jig, measure 2 1/4" in the direction of the router and mark that spot. Drill that location. The extra 1/4" was for the diameter of the bit which can't be neglected.
Attach the router and jig to the bolt with a nut. Double check by spinning the router around the circle to see everything is located in the right spot. Set your plunge depth and begin cutting the circle, 1/8" deep at a time. I plunge to a total of 1/2 inch.

[workin for wood]

Now remove the circle from the MDF. Using the scrollsaw, cut away the scrap portion of the circle, staying wide from what the actual final dimension of the circle will be.
A spiral flush trim bit is installed into a router inside a table. The bearing will ride against the wall of the circle that is already routed out. In essence, the circle is it's own template. A spiral bit is preferred as it has a lower risk for tear out, especially with figured woods.

[workin for wood]

Re-mount the circle to the MDF in the exact position it was originally in. Same letters, same screw holes. I marked a dot 1/2" either side of the split marks on the inside of the circle. I did the same thing only 1 1/2" on the outside of the circle. Using the regular base for the router, I joined the marks together to form a curve. I then measured back another 1/2 inside and outside this time and marked a dot. I used same router base and connected the dots for an identical curve. The first curve is the actual cut line that will separate or quarter the circle into 4 separate pieces. The second curve line is the stop line for a groove that will be installed into each section. Not a through groove, but a stopping groove, which is a more impressive and attractive detail.
2 new holes are drilled into the jig. All depends of course how many grooves you want and how wide your frame will be. For me, divide the width by three and that is how far the holes are apart for 2 grooves.
A v bit is installed into the plunger and the depth guage is set. I install mount the jig with the bolt as before. I set the bit over one of the lines where the bit will stop/start. I use a clamp or piece of wood and the clamp becomes a dead stop. Can't count on steady hands with a router. I put another clamp on the other side as well. Do a test with router off, be sure it's all set to stop on either sides, Plunge down in half way starting in the center and working to either side, then re-plunge the full depth and complete the groove. Repeat the process for all 8 grooves. Do not let the router sit in one spot, especially in a corner as it will burn the wood. Some burning may be inevitable, but the less the better, as it will be easier to sand out later. Do not start the plunges at the ends or burns will be guaranteed.

[workin for wood]

Now the wrapping of the frame begins. I dimensioned some quilted maple. The wood was cut into thin strips and all the strips fed through the drum sander. The strips will be doubled up and glued around the circle. For now, only the outside of the circle is wrapped. This requires a multitude of clamps. I didn't have long enough strips so I am gluing half at a time, the strips stopping at the center lines where the circle will be quartered anyhow.

For the rails and stiles, the boards where dimensioned and laminated. They will also be wrapped, but only a single wrap twice as wide as one of the strips is necessary. The strips have to be extra thin in the circle in order to bend. More on those later.

[workin for wood]

When the circle is dry, the bottom side is cleaned up with a palm sander. Nothing fancy, just making sure there's no glue and no edge banding protruding that will make it un-flat. The curves are extended on the cut lines using the same circle template used initially, which in my case was the router base. The curves are then cut out with the scroll saw, staying a bit outside the line. There is no way the saw will cut a perfect curve, especially in wood this hard and thick, and maintaining 90 degrees at the same time. Once all the quarters are cut out, the ends are sanded flush to the line using a large spindle in the oscillating spindle sander.
The curves are too tight for the thickness of the edge banding to bend too without cracking. This is solved by soaking the banding in water, which will allow extra flex.
A jig is improvised in order to clamp the ends in place. I am using a stool, I waxed the surface of the stool to prevent glue from sticking to it. The curved piece is dry fit tested using the edge banding until a perfect match is obtained. The the pieces are glued into place and allowed to sit for at least an hour, then on to the next piece. Once all four pieces have one end glued, they will be trimmed. The holding jig may require a slight modification since the curve at the end will have changed a bit, but the clamping caul will likely remain the same. It's not complicated, just time consuming.

[workin for wood]

Measure the width of the circle not including the banding. This is the width for the rails. One edge of the rails is jointed, and then they are trimmed to the proper width, adding just a 1/32 or so to the width. The sawn edge is then jointed. The two edge banded pieces around the circle combine to be 3/16. Strips are cut and milled at 3/16 to band the sides of the rails. They are glued on. Once they are dry, glue is scraped. The edge banding can't be expected to be a perfect flush fit to the faces of the rails. Hold one edge tight to the fence on the jointer and joint the bottom of the rails to be square with the edge. The drum sander will be used to sand the top of the rails flat and flush with the edge banding, the boards flipped and the bottom sanded until desired final thickness is obtained.

[workin for wood]

After the rails are milled to their final dimension, a 3/4 sheet of MDF is cut and squared to the in side dimension of what the frame will be. This will become a template and ensure that the frame remains square during assembly. The rails are simply crosscut to fit around the outside. The idea is that the quarter round sections will be placed on top of each corner, lined up to match all the way around, traced to the rails, so that the rails can be cut to match.

This will be a while, the banding on the ends of the rails takes more than an hour to set because of the soaking. Probably take 3 working days to glue all the ends. But at least we can start to get a vision on the final result.

[workin for wood]

The ends of the circles are trimmed with the saw and flushed with the spindle sander. The rails and styles are clamped to the template board and each corner is lined up in it's proper place according to however you desire them to be. They are traced onto the rails/styles and the frame is then cut. I use the scroll saw to cut the arcs and the spindle sander to clean the cuts to the lines and make any minor adjustments to the fit. Once all the corners fit, the final side of edge banding is applied to them.