Tough veneering job


Some simple veneering and inlay work I can handle, but this one I can't figure out. The piece is a solid strip of walnut, about 3/8" thick and 2 3/4" wide. It's flat but curves in length, it's for a dashboard in an old car. A trough has been cut in the middle of the piece to allow for two pieces of bookmatched veneer and a thin, white inlay border around the veneer, with the solid wood forming a border at the perimiter. One, cutting a perfect "trough" would be very difficult using a router table setup, near impossible considering that the ends have to be squared off within the solid wood. Two, what technique would be used to get the veneer and inlay to exactly the right size? The piece can be seen at: http://www.edswoods.com/appendix Any leads to good, on-topic sources of information about this subject will be greatly appreciated.
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Whoops, I see my link didn't work Try http://www.edswoods.com/appendix.html or just www.edswoods.com and click on Appendix.
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wrote:

I'd be inclined to try using a template with a cutout the shape of the trough but enough larger to allow the use of template bushing. I'd (re)route the trough so it matches the template (except smaller because of the bushing). Then I'd change the bushing and bit size to route a piece of veneer (temporarily attached to backing) so it was smaller than the trough by whatever thickness I wanted the inlay to be. Place the inlay, and then the veneer.
It would take some fussing to find the right combinations of bit sizes and template bushing sizes, but you should be able to make it work, even if you have to wrap a few layers of tape around a bushing.
When routing the veneer, you have to keep the router tight against the template or the veneerwill be ruined, but it should be doable.
Or....
You could make a template the shape of the trough but smaller, and use two different bit sizes and bushing sizes to route the veneer and the trough. But this way if the router slips you ruin the piece, not the veneer.
There are commercial inlay router bushing kits that have a special bushing with a sleeve that perfectly compensates for the bit diameter. But you need three different sizes because of the inlay.
HTH,
Paul
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swollenthumb wrote:

The original piece can serve as a template for routing the outline of its replacement.
You could use a router guide bushing and a 1/8" down spiral bit (Lee Valley and WoodCraft both sell these as inlay kits) in conjunction with a hardboard template to cut the trough /and/ the inlays. A marking gauge would probably make the layout fairly easy.
It might be a good idea to do a practice run with some cheap pine and some inexpensive veneer before you go after the "real deal" - it'll let you test your templates and develop a good feel for what you're doing.
I have a CNC router in my shop and my approach would be a bit different: I'd chuck up a fine-tipped probe to capture the shapes of the parts, then use that data to machine new parts.
The first method would probably be faster and provide greater personal satisfaction (if it's your own car); and the second method would probably involve less human effort and possibly increase precision.
--
Morris Dovey
DeSoto Solar
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Lee Valley's inlay kits work great. One thing to look out for, is to keep the router pointed in the same direction throughout the whole process. Odds are that the router bit won't sit smack in the centre of the bushing(s). Also, the inlay kit I received had an odd-ball size guide bushing, didn't fit my standard PC base. I don't know if that will apply to you.
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Thanks for all the replies, I'd like to get good at this. It's hard to believe they cranked this stuff out on a regular basis. And it's funny, you see more inlay work on the earlier cars from the 'teens and 20's than on the later ones that fetch all the money. It's as if the inlay was considered gaudy or inelegant after that time. At any rate, if at some point I feel I can't do it, I'll be looking to job the work out somewhere. It's interesting that it could be done on a cnc router.
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Maybe the piece is a 1/4" thick oversized piece of walnut to start with. Then the central veneer was applied. Then an extra wide outer band of walnut 1/8" thick or so was applied, then the whole thing cut to the right outside dimensions. Or maybe you could do it that way. Sam
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wrote:

What are you trying to do here? Replace the veneer and stringing, or re-make the whole piece?
If you're just veneering it, then I can't see where a bench-size router fits in at all. I'd veneer the centre, then use a hand-held purfling cutter to put in the groove for the inlay. I know some people use a Dremel and a tiny router base to do this, but I've never liked them IMHO.
It doesn't look lke a big deal at all. The little curvature there is is along the long axis, so veneering the main surface isn't a problem. The inlay is simple and sufficiently straight that slight flexibility will be enough to let it fit.
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Andy Dingley wrote:

pieces of

Gotta make the whole piece.

I'm not familiar with a purfling cutter. I'll find it on the web. Does it follow the contour of the piece the way a marking gauge would, and make a clean cut without tearing up the grain?

problem. Are you talking about veneering the entire top surface? What about the rounded-over ends?
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wrote:

Find a copy of Zachary Taylor's "Decorative Inlay". Recently out-of-print, the bargain bookshops (and eBay) are flooded with it.
Purfling cutters are a tool of the luthier and instrument maker. They're a bit like a marking gauge, but they have knives and usually two of them. The guide bar is curved, to allow a curved edge to be followed, and most people have either several different different shapes, or one that has interchangeable bits.
The best one ever was made by Karl Holtey, but I think this was a one-off (it's in the Taylor book). Any machinist can knock you up a crude non-adjustable one, and a couple of crude ones will do what the Holtey multi-angle one does.
A good trick for making purfling cutter knives is to buy some O-1 steel sheet, the ideal toolmaking steel that comes in small ground-flat strip packages from any engineering retailer. This stuff is easy to work and can be hardened and tempered in a kitchen. Use sheet that's _half_ the inlay thickness you want, grind the edges of a pair of knives as handed single-edge knives, then simply put them together bevel to bevel. Much easier than cutting knives and trying to adjust their spacing.

Better than a marking gauge - you're not trying to track a curve with a flat face.

Looking at the picture I thought this piece was secondary timber (maybe straight-grained walnut) that was visible around the edge, with an inlay of burr walnut. That's how I'd think about making it - I might use a clamped mitred end (like a Japanese tansu door) of the same timber to put straight grain across the end pieces.
Assuming the whole piece needs to be veneered, then this sounds like 5 pieces. The edges are done in four separate pieces, with mitres in the corners. A fairly flexible veneer is used and a vacuum bag press is used to hold them down. If it's awkward, do the two long edges first, then cut the mitres, then attach the end veneers and bag them again. After the edges, use the purfling cutter to trim the inner space for the central inlay (this doesn't even need to touch the four outers) and veneer that. Finally go round with the purfling cutter again (same settings) and cut for the inlay stringing.
--
Smert' spamionam

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Are you familiar with Constantine's purfling tool for 48.00? I'm going to call and try to talk with someone who can explain the tool. (www.constantines.com) If it has a curved edge, wouldn't it wobble on a straight one? I have to do some straight pieces as well. I would guess they used this method on the straight pieces because the grain on the inside and outside borders of the inlay match.
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wrote:

I'm in the UK, not the USA, so I don't know them.

I can't see any guidance on this, unless it's just used for cutting rebates in an edge rather than a groove inset some distance.
Also it's an adjustable knife, rather than the fixed knife I prefer (with multiple tools).

Depends. If it's a cylindrical guide, then it may wobble (hand technique can avoid this). If it's two half-round bars on a flat face, then it will guide on either flat, concave or convex. Although it can't handle a small radius concavity.
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In the photo, it looks like the outer band of walnut is raised above the veneer and rounded over. Does the inner veneer and the white band sit lower than the outside band of walnut or is every thing flush? Sam
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snipped-for-privacy@yahoo.com wrote:

Sam
Everything sits flush, but the outer edge is rounded over, on all four sides. What might be giving the illusion is that the piece is slightly dished in, being older than the Little Rascals. I have to do this piece and 4 sections of door trim. The door trim pieces are straight and would be easier to do, giving me more of a chance to develop a technique. I've been looking at some of those shop-made electric purfling cutters and I'm going to make one, suited for my purpose here and not violins. I've got some pieces of rosewood laying around from a marimba factory and I'll use some of that wood for parts. I did a sketch of what I'm going to make in a 3d graphics program, but don't know which bit to use yet.
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Well...I borrowed the plunge tool for a Dremel. It's got an edge guide, and I bought one of those flat-bottomed, carbide burr bits (not a router bit.) The smalles router bit at Menards for the Dremel is 1/8" which is way too wide for my inlay strip. The original strip is only about 3/64", and if I find anything at all that narrow it will probably be online and I'll have to wait for it. I've been practicing with lengths of poplar and 2" iron-on walnut veneer strips, setting the border about 3/8" in all the way around. I can do it. The bit has to be set as deeply into the tool as possible to avoid wobble and the base has to be blown off constantly to remove fibers. The list of problems hasn't been overcome yet. 1. I'm not sure I've found the optimum bit or will be able to. 2. I need a good way to clean up the fuzz on the edges of the cut,
especially on the endgrain. 3. I will need nice, clean uniform strips of something white and sandable, 1/16" thick maximum and the width of whatever the cut turns out to be.
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Had a pretty good few hours with the inlay project. I gave back the Dremel tool and took back the bit. I made the solid wood part, then a template the size of the inlay. I have one of those Japanese handsaws with a curved profile, so I just used that to cut the border around the template, and finished off with an xacto knife. The kerf is the 3/32" I needed! Freehand routing the center wasn't too hard, I finished up with a sharp chisel. Then I found a good use for the cheapo 9" bandsaw from Menards. I set up a straightedge and it did a good job of ripping the inlay strips from hard maple. Tomorrow I'll cut the pressure-sensitive veneer that goes in the middle the size of the template, lay it in, then hopefully I can lay the template back over where it was before and just open up the groove with the handsaw. We shall see.
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Well, the inlay job turned out satisfactorily, though I wish I'd had more selection when picking out my walnut. I'd give it a B. If you'd care to see, go to http://www.edswoods.com/appendix.html
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swollenthumb wrote:

Definitely an improvement. Nice work!
--
Morris Dovey
DeSoto Solar
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