Official Luthiers Forum!

Hey all,

A new member sends greetings from New Mexico. I've enjoyed lurking these last couple months but a slight problem has pushed me to step forward:

Using the techniques described in Cumpiano's book, I routed rosette channels for a steel string I'm making, my first build. The router is a good Craftsman with a new 1/8 inch bit, but it left ragged, or "toothy" edges on the channels owing to the different densities of the growth rings in the spruce. When I filled the rosette channels with a mixture of ebony filings and glue the color contrast between the spruce and the ebony emphasized these toothy edges even more.

How can I get smooth edges on my routed rosette channels the next time?

Thanks,
Brian Pottorff

You can use a downward spiral bit to get a clean edge, Stewmac sells them. Leaves a nice clean edge.

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Jonathan Kendall, Siloam Springs AR

Cumpiano shows a "popsicle stick" rosette cutter in his book. I use something similar to this to precut the edges of the rosette channel. This eliminates the "fuzzies" when I route out the channel and helps to reduce the possibility of chip-out. Of course, as Jon mentions, a good downcut spiral bit is a must.

Best,

Michael

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Live to Play, Play to Live

Another technique is to wash coat the area with shellac before cutting, you will find you get a much cleaner edge.

Oh and make sure you rotate Anti Clockwise.

Todd

Does your die grinder run on Air or Electric ?

I had this same problem when I was using a Dremel with a downcut spiral. It completely went away when I switched to a laminate trimmer. I also wash coat the area with some shellac.

-Mark

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Pullman, WA

The more I know, the more I know I don't know.

trippguitars.com
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Welcome, Brian!

Nothing new to add that wasn't said above. I wash coat with shellac, and then use a dremel on highest speed with a Stew-mac circle cutter and base, and small spiral downcut
bit.

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Jim Kirby
kirby@udel.edu

Hi Brian,

I echo Todds comments, the air grinder cuts much better than my dremmel did. I have mine mounted to a http://www.microfence.com/ which improves setability. I always under cut the dimension by .010" then wash coat again with shellac, when dry cut to the final diameter. The main reason I do that is chip removal, many times bit deflection is due to chip loading and packing. Downcut bits do not remove chips well. Small diameter bits can bend, so getting rid of the majority of chips before the final cut helps keep everything true. As Russel says I always move the tool counter clockwise. FWIW my 2 pennys.

Keith M38938.4362731481

I've had great results with a Dremel, but the key is to route the rings close to size, and then take away the final material a little at a time. This has always given me very smoothe edges with no fuzzies.

Good luck!

John

P.S. Welcome to the forum!!!!!

Just take a flat sanding block and "cut" the fuzzies off with 220 paper or so. I usually sand them against the grain so they don't tear out. Just use a light touch.

This is one of those areas where an ounce of prevention is worth a pound of cure.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I too use a dremel with excellent results. Maybe you tried to cut the whole channel in one pass on the outer or inner edge. Just take many shallow passes as you work your way outward towards the outer edges. Easing into it should work for you. Another tip, always cut your rosette channel in scrap, and make a scratch mark on the circle cutting jig to mark the location on the inner and outer diameter, so when you use it on your top, you will know where to stop. Hope this makes sense.
Tracy

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Tracy
http://www.luthiersuppliers.com

I find it best to rotate counter clockwise on the outside of the circle & clockwise on the inside.
I have a 1/8" & a 1/4" downward spiral bit that I use only for rosette cutting & replace 'em as soon as they start to dull.

What's a shellac wash coat?

If you make a 1# cut of shellac and wipe it on your top before you start cutting it will help with the fuzzies. You can also use it to seal the channel if you are going to glue in the rosette with CA (superglue).

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Brian,
Here's a few photos of a rosette cutter I made modeled after some of the other forum members designs. (Can't take much credit...)

Cut the inner and outer radius (carefully) and you probably can use any type of router bit you prefer.

I used a 1/2" bolt, a scrap from a walnut spindle, a 1/4-20 studded knob from my jig box, a threaded insert, a 3/16 pin and then made a few blades from an old hack saw blade. The only time consuming part was drilling and tapping for the small set-screw.







Cheers,

Pete

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Peter

Nice...

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

The main ingedient to a good clean cut is proper technique and a sharp tool. When I do rosettes I will use the cutter for 2 rosettes then replace it. I to like the wash coat to help support the wood fibers. I like to work from inside out. I like my last 2 passes to clean up the outer cuts so I have a nice clean look.
I don't use downward spirals as the chips are forced into the cutter and will create heat and that dulls the tools faster. If you want to use them be sure to have ait to blow the channel clean and keep the chips out of the way of the cutting edge.
john hall
blues creek guitars

Hey Brian,
Welcome to the forum. I just noticed your from New Mexico.
I'm in Los Alamos, Close at all?

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Jim Watts
http://jameswattsguitars.com

Hey Jim,

I'm down in Deming. Once in awhile I'll get up to Albuquerque, maybe even Santa Fe.

Well, next time your coming up to Santa Fe maybe we could get together.
Let me know

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Jim Watts
http://jameswattsguitars.com

[QUOTE=BrianPottorff] What's a shellac wash coat?[/QUOTE]

Brian,

This is what I use for a wash coat, the spray can on the right. About $5 at the local Lowes or HD, and works well for sealing rosette/binding channels prior to gluing, or before I cut them, to help limit fuzz or splinters.

Jeff