Turning blank type thingy...

I have a piece of Doug Fir that's 4x4x96". I want to wrap it in, say, walnut, so that as you look at the end you see a square of end grain Fir with 3/8" of end grain Walnut around the outside, and the Walnut meets at the corners in a miter joint - not a butt joint. Any ideas on the best way to apply and cut the walnut skins so that the miters (bevels?) meet nicely along the entire length? I was sort of thinking some sort of router set-up where I glue on a skin oversize then rout the miter/bevel into it. Sort of like a reverse or upside down chamfer bit set-up. JP
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 Sort of like a reverse or upside down

I am not sure you can bevel\miter it in place. I would first make a small piece mitered at one edge to use for setup. Do one of the sides with miters but slightly oversized. Use the sample piece to line up one edge and check the other edge to see how much needs to be taken off. Use other sample pieces to setup the TS fence to try the new reduced size, then do the final cut on the first side once you have it dialed in. Attach the first side.
Then just work your way around the faces. Fit the new miter edge to the existing edge and check the next side with a sample. Use a sample to set the fence and try the next miter, etc.
You only really need a tight fit at the ends so you can do a bit of fudging by sanding down the fir a bit to help close a miter at the endand pullin the walnut with clamps.
Not sure of the exact design but it would be much easier if you just had to fit up short pieces at each end and then run rough fits down the rest of the beam between to two ends. If you undercut one side that is a lot of 96" walnut to thrhow out and start over.
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Cut the miters at 44.75° - 44.90°...., if you can, so that only the outer edges touch. If there is any space showing on the endgrain, fill it in with some small slivers. If you're more accurate with the miter cuts, maybe the glue will fill in any endgrain spacing. A slight glue line, on the endgrain, might be hidden with some fine sawdust mashed into it, also.
Sonny
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On 1/26/2012 4:53 PM, JayPique wrote:

Lets say you get to where you want, do you think the fir will be stable enough through temperature/humidity changes to not open the walnut joints?
I did a similar glue up with oak wrapped around hollow "plywood posts" to form bed posts. And did in fact use butt joints. Over two years they have remained stable. BTY the oak was 3/16" thick.
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Expansion and contraction issue: Another option would be to cut the corners off the 4X4 fir and either use the central portion of the fir, allowing the walnut edges to expand and contract, or use the short face triangle cutoff corners of the fir (attached in the corners of the walnut skin), allowing the center portion of the walnut to expand and contract. Still, though, cutting your walnut bevels just shy of 45°, so that the outer edges attach tightly.
Sonny
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There is a slight differential in movement between walnut and fir given a humidity change, but remember that as you look at the end of the blank all you see is end-grain of both the fir and the walnut. Does this change anything?
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By attaching the two woods, either way, you would be reducing the amount of contact between the two woods, hence reducing the expansion/ contraction effect one will have on the other. If you have the spare lumber, make 2, foot long, test pieces, one each design, and subject them to a range of conditions.
Sonny
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"JayPique" wrote:

-------------------------------- Something to keep in mind, it will be nearly impossible to maintain a sharp wooden corner in the real world over time, so take advantage of it.
Plan on breaking the corners with a 1/8" round over router bit or suitable hand plane.
With the corners broken, it will be much easier to hide the joints.
Have fun.
Lew
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On 1/26/2012 4:53 PM, JayPique wrote:

    I can't imagine any dimension lumber being consistent enough to even think about attempting this. If the core were MDF or plywood you would have a better chance. It will be fairly difficult to cut the walnut strips with a true 45 degree full length on each side. I own some decent equipment and I wouldn't attempt it on anything that long. They don't make enough hold downs, edge guides, leading and following tables. Is the 4x4 structural? what is the reason for the mitered edges?
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This is more of an exercise in planning than an actual project. I have since found reverse-bevel bits that are used in countertop fabrication, which, if I removed the bearing, could be mounted in a router table with an offset fence such that it would cut and trim the miter appropriately. I wasn't thinking of using wet dimensional lumber as the core, I was going to use kiln-dried, straight-grain, rift-sawn Douglas Fir. (that's a mouthful, huh?!) The mitered edges are needed because I was planning to slice the blank into a couple hundred end-grain coasters!
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On Sun, 29 Jan 2012 07:39:03 -0800 (PST), JayPique

Ever considered _sobering_up_ and rethinking that one, Mark? <bseg>
-- The most decisive actions of our life - I mean those that are most likely to decide the whole course of our future - are, more often than not, unconsidered. -- Andre Gide
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What does "3/8" of end grain Walnut around the outside" mean? Are you talkin' quartersawn? I've never seen a 96" wide stick of walnut from which you could cut end grain.

I'd guess you wanted to dress the 4x4 down to remove the radii, then start fresh with the thick veneer. You could probably do the miters on a table saw with holddowns and featherboard. Do you have a micrometer feed on the fence or a jig for that? It would be highly recommended. Ditto on a router table, but it would be dicier without long infeed and outfeed tables connected, featherboards on both sides, and a holddown on either side.

Good question.

For clean, seamless edges. I'll bet.
-- The most decisive actions of our life - I mean those that are most likely to decide the whole course of our future - are, more often than not, unconsidered. -- Andre Gide
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