How I cut rings for rosette

[btberlin]

I needed to cut some rings of cocobolo to try out some ideas i had for a wood and mop rosette for a cocobolo/sitka J45 that i am building. The difficult part was holding the piece of veneer still while using the trammel cutter. Double stick tape almost worked, but didn't have enough grip. Masking tape was a dud. So, out came the trusty can of 3M type 77. I like this spray stickum because it doesn't overspray - so i can use it at the bench without getting everything else sticky, and, it has just the right amount of grip for the things i do. So here is what i did-

I found a piece of scrap plywood to serve as a base. In that, i drilled a 1/4 inch hole (with a forstner bit to insure a good round hole) where I wanted the ring centered. Then, i resawed some cocobolo into veneer, and marked out where i wanted the center of a ring to be cut. There, at the center, i drilled a 1/4 inch hole with my forstner bit. I flipped the veneer to the "underside" and sprayed a couple of lines of type 77. On the plywood base, i did the same. After a few seconds for the solvent to flash off, i stuck a 1/4 inch drill shank through the veneer hole, and used that to align with the hole in the plywood. Slid the veneer down the drill shank, and voila - stuck it to the plywood. After removing the drill bit, I inserted the trammel cutter pin into the hole(s) and made my rings. The photo gives an idea of how the elements were arranged. Using a Forstner bit to make the holes insures no wiggling of the center pin of the trammel, keeping the ring nice and circular. The trammel cutter shown in the photo is a home-machine-shop knockoff of a guide i saw online somewhere - i didn't invent it.

bert

[Stray Feathers]

I'm resurrecting this earlier thread because I am at this point with my first build. For clarity, it makes sense to me that it is better to cut the inner edge of a wood rosette ring first, no? And secondly, how do you get the adhesive off the back to glue it into the channel? I tried cutting some rosewood that I thinned successfully with a thickness sander, using a rotary tool with a Dremel circle jig, but they are not perfect circles. I am thinking about countersinking small screws in the outer corners of the rosette stock to hold it firmly, and then cutting the inner edge first, and then the outer. Another option - I'm in the picture framing business and have a circle/oval cutter for mat board, and wondered too if it would work on veneer or slightly thicker material for rosette rings. It uses what looks like a pointed Xacto blade which is very sharp and inexpensive. Anybody know of anyone who has tried this? (Mats are usually cut with a bevel, but the cutter can also make vertical cuts, and cuts are easily made deeper in steps.) Maybe I'll be the guinea pig . . .

[btberlin]

Well, first, the 3M type 77 was not at all difficult to remove (3M makes a few different spray adhesives of differing strengths). I did this quite a while ago so i don't recall exactly how i removed the adhesive, but if you look on the spray can, a clean-up solvent recommendation is provided. I believe I also scraped residue off with a sharp cabinet scraper, but you could do the same thing with a single-edge razor held perpendicular to the surface of the ring.

I also do not recall whether i cut the inner or outer diameter first. I can tell you, though, that the 3M 77 held the workpiece very firmly to the sacrificial board underneath, so i can't think why there would be a preference for OD or ID first. To remove the finished ring i used an inexpensive (from a restaurant supply) cake-baker's frosting spatula. For a couple of bucks, these are so handy for a lot of things that i have them attached to the edge of my workbench with a couple of magnets.

My experience with trammel cutters tells me that if you secure the sheet of veneer with screws, that last part of the last cut will get messed up because the ring will move when there is hardly any material holding it to the sheet.

I was cutting the rings out of cocobolo which is pretty hard and brittle stuff. and the material was re-sawn, then planed and sanded to about the same thickness as the top. I have no clue how repeated cuts in rosewood might work out, but i predict that the repeated successively deeper cuts will leave an edge that is not really clean. But, by all means, give it a whirl.

good luck, and welcome to the "club"

bert

[johnnparchem]

If you have a drum sander ... Start with a thicker veneer than you want for the rosette, Route the inside and outside only to the depth you want for the rosette, sand off the back until the ring drops out. That is how I do it.

[Stray Feathers]

John, your method is clever! I will try it.

Meanwhile, I pulled out the circle/oval mat cutter at our framing shop and tried cutting rings with it. It worked quite well (though my experience is limited . . .) One minor issue is that the blade holder for "straight" cuts is actually set at 85 degrees, apparently so the cutter will handle circles better. On a thin ring it is virtually unnoticeable but may be an issue at least on the inner edge and may need some judicious sanding. In the photos, the black bar clamps the work down; I also used a clamp on the outer end. A piece of mat scrap is used underneath as a slip sheet for the blade to penetrate in finishing the cut. The black and silver disc on top is the adjustment for the offset for ovals; circles have a zero offset. The long handle gives good control when making the cut. In the closeup, the knurled wheel at top lowers the shoe to the material. The blade is lowered by turning the lower knurled knob in increments with each rotation. (Another blade holder is used for normal bevel mat cuts, and there is a glass cutter too.) The blades come to a sharp point so can handle curves easily, and are inexpensive so can be changed for every job if necessary - we buy them in a box of 100. This is not a tool you will want to go out and buy for a few rosette rings, but if you know someone who has one . . . I'll follow up on whether the slight bevel on the edges is a problem.

circle cutter 1.jpg

circle cutter 2.jpg

[JLT]

I've had some luck with double-sided tape. The trick on releasing it from the sacrificial board is to heat it gently. I use a hot-air blower (the kind that you use for heat-shrink tubing) but I think that a hair dryer or electric iron would serve as well. The heat softens the glue, and the veneer peels off. If there's any glue left on it (and there usually is), I wait for it to cool and then scrape it off, or lift it off with more of the same tape.

[Stray Feathers]

The double-sided tape we use in our framing shop comes off easily by rubbing/rolling it with your thumb - the sooner you do this the easier it comes off. It may be different from what you are using because it only applies adhesive, not a separate film with adhesive on both sides. The paper "tape" rewinds back into the applicator, leaving only the adhesive behind. You can use it without an applicator by sticking it down and manually removing the non-stick paper layer but it's fiddly. One brand is 3M ATG but some framing suppliers sell their own house brands. I'll test it sometime on wood for adhesion and removability.