fiveeyes wrote:That sir, is just outstanding!! I am looking forward to the top.
Thanks fiveeyes. Patience - it's coming.
I started to tackle the top in exactly the same way as the underside. I had some cherry 60mm thick and 240mm wide. The central disk will be 1,000mm in diameter, so 3143mm in circumference. This means that I need to get 16 veneers from my stock, each one 200mm wide. That allows 3.75mm per veneer. I want each veneer to finish at 2mm thick, so need to cut them at 2.5mm to allow for any unevenness in the cutting, which I can take out on the drum sander. I need to keep reminding myself that every veneer will end up at the thickness of the thinnest piece. That’s an allowance of 3.75mm per veneer including the kerf, so having practiced on some scrap it seemed doable. When I came to cut the cherry, I ended up with only 14 veneers. Bummer! That’s not enough to get a symmetrical and uniform starburst. I decided to try again, and again I ended up with 14 veneers. Double Bummer!!
Anyway - it is what it is. I went on to cut the birdseye maple (BEM) veneers and guess what? Without touching the set up of the bandsaw I got 7 veneers from a plank just 22mm thick. That’s only 3.14mm per veneer, including the kerf. That means I should have got 19 veneers from the cherry. Go figure! I don’t understand it! The key thing is that I now have more than enough of my prized birdseye maple, so it’s not a disaster. These are stacked “in stick” indoors for just over 2 weeks to allow them time to stabilise.
I decided that the way forward would be to use equal veneers from both sets, in alternating pairs of 2 bookmatched veneers. I cut a template from some scrap ply to get the angle right in the centre i.e. 22.5 deg. . Here is the disk set out with one set of segments from one batch in place, and the others ready for cutting into segments.
- inner cherry layout
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The end pieces of each semicircle were cut oversize to allow for trimming, and also to allow room for further shrinkage, having learned the hard way with the underside. Here are the two sides roughly laid out and ready for each edge to be shot straight ready for joining, which I do as before using the router on a rail technique.
- rough halves
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Here are the 2 sides assembled ready for trimming and joining together.
- taped halves
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I draw a line along the edge and leave it a couple of days to see whether there is any further shrinkage across the grain. Hooray - there isn’t!
- shrinkage check
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I rough cut the 2 halves to size in a straight line with a hand saw, leaving perhaps 3mm to be removed accurately. Time to shoot the 2 halves straight, ready for joining which I do as before using my little Makita trim router on a Festool rail. This works particularly well for this task, as one half of each cut is against the grain, so would be difficult with a hand plane on a shooting board. Even so, I take it slowly, just trimming away about 1mm at a time with slow passes of the router.
Before joining the 2 sides together I place them on the table and line up the focal point of all the segments with the precise centre of the table. It is much easier doing it now rather than when the disk is assembled because I can actually see the central point. Then I draw around the complete disk, so that I can place it in exactly the right place when assembled.
Having joined the 2 halves together, I immediately glue them to the table top as I’m not going to give it time to move, again using West Systems epoxy with the 206 slow hardener and colloidal silica as a thickener exactly as before. Remember to mix the resin and hardener well first, and only then add the thickener. This is because the 206 hardener is much thinner than the resin, and the thickener would soak it up and the curing would be uneven. There is over an hour of workable life once mixed so I can be calm and methodical setting it up. Then into the vacuum bag for about 6 hours. Once it starts to go off - about 90 mins - I cover it with an electric blanket and duvet to speed up the curing. At least then it is sufficiently cured by the evening to be able to turn off the pump!
- pumping
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Once out of the bag I take off the tape so that the adhesive isn’t left on the surface of the table. The central points have pulled in nicely.
- central point
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Next job is to trim the cherry circle to its final diameter, so on goes the router and trammel again, just like last time, so no new photos. Then I arrange the BEM veneers around the circumference, bookmatching where possible, and making sure that they are all approximately the same width. The width of the veneers dictates that there needs to be 20 pieces, so to ensure even spacing, I make sure that each quadrant has 5 veneers, and shoot the edges to join them together and glue them to the table, 2 at a time this time, just like I did on the underside, using a plywood platten held down with cauls. The final piece is cut marginally oversized, so that it is a snug fit just short of the cherry disk.
- last piece - slightly oversize
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Then I take a thin shaving off the edges, retrying after every shaving, until it is a snug fit. I focus on getting the sides right as the join with the cherry will be filled with a 3mm string of ebony and sycamore.
- last piece - snug
- (158.25 KiB)
Time to cut the groove for the stringing again. I have to confess that this is when my bum starts blinking like a camel in a sandstorm!
On with the trammel again, and line up the 3mm cutter with the join between the cherry and BEM.
- line up the 3mm spiral down cutter
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I’ve attached a mini LED spot light to the trammel arm which makes for really good visibility. I have a couple of these which I also use on the band saw and router table. I then slowly walk one full circuit with the router to make sure it is lined up with the join all the way round. No reason why it shouldn't because the pivot point has not been moved, but always nice to get confirmation. It also helps ensure that everything is tight, not moving, and that there are no trip hazards.
- trammel set up for stringing groove.
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I check that all the thumb nuts are tight and that the cutter is firmly locked in place. The strings have been cut 5mm deep, so the groove is going to be 4mm deep. Close the garage door so no one coming up the drive tries to speak to me mid cut (the buggers invariably do), take a deep breath and go for it.
- Groove cut.
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All goes without any drama. Yay!
For the underside I trimmed the excess string off with a router, but this time my nerves won’t stand it, and having left less string proud of the surface - around 1mm or less - I trim it flush with a scraper. Far less harrowing!
- Trim excess with scraper.
- (298.03 KiB)
All comes out nicely. That’s the top more or less complete.
- top stringing.
- (281.83 KiB)
The trammel hub will remain in place as it will be needed to trim the table to its final diameter before fitting the 25mm wide cherry edging. However, I’m leaving that for the time being so that the edge is less prone to damage.
- top complete
- (239.08 KiB)
I’m not unhappy with the result. The BEM really “pops” in the light, and almost seems to "flash" as you change your viewing angle - the photos really don’t do it justice.
Next job is the skirt which I’m going to laminate up in air dried ash and veneer with cherry. However the ash is at the bottom of my timber stack, so I’ll have to wait for a reliably dry day to lug a load of wood outside to get at what I want. Sunday is looking favourite.