Official Luthiers Forum!

Anyone seen one on the net?

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I like that
the f.b does not cover it at all?


mike

_________________
Mike Collins

I would imagine the pic is during the build rather than the finished instrument.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Doesn't look like there was any planning involved in that one. Probably the thick radial line at the upper left was routed first. Then some random length arcs at the inner and outer radius of the lighter wood inlays. Then do some more radial lines to define the ends of the inlay sections, and glue those in along with their purflings. Then route some more random length arcs at the inner and outer radius of the dark wood inlays, more radial lines, and install those and their purflings.

The wood inlays could either be cut separately using the same circle routing jig so they fit in together with the purflings, or you could rough cut them, glue them in, and re-route the purfling channels around them.

This is a much simpler one. The long burl segments were cut with a circle jig, then inlaid and routed for the black trim. The "link" pieces were also cut with a circle jig, fine fitting done on the link pieces.

_________________
formerly known around here as burbank
_________________

http://www.patfosterguitars.com

I can't tell from the photo in the first post, but I'm guessing that the ends of the thin purfling lines that extend out by themselves are squared off. I'm wondering how you would make the end of such a thin recess nicely squared off to match a squared off purfling end.

Is there a trick way to rout the radial lines so that they are truly radial or do you just clamp something to the top to act as a guide for the router for each line?

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I would inlay the wood sections first. Then put in the lines- should be easier and cleaner as long as the purfling materials are selected to match available router-bit diameters.


Steve

_________________
Steve Smith
"Music is what feelings sound like"

Very nice! I love it when normally flat areas include some 3D features.


I can't tell if the purfling ends are squared off or rounded. The thick black radial lines do have visibly rounded ends.
Squaring off the ends of the channels would indeed be a bit fiddly, especially if you have to cut into any dark grain lines. I can't think of any tricks. Just poke at it with a small and very sharp chisel.

As for the radial lines, yes, just clamp something to the top to act as a guide. To get it perfectly radial, place the router with the bit at the center of the soundhole, and push the guide up against the edge of the router.

Here's one that I've just done:



...and here is another.

A quick guide:

1) You need a really accurate, solid, router circle cutter (and sharp bits) where you can repeat the setup of the cutting radius to better than 0.05mm. There are some pics of mine over on the ANZL
2) Plan out your rosette (radii, block widths, angles, etc.). Draw it on paper and copy it to the soundboard (even gluing the paper to the soundboard if that helps)
3) Cut out the fills first. Make sure the veneers, shell etc. are solidly held (double sided tape or similar). The arcs of segments must be concentric. Try to cut blocks of the same radius (maybe in different materials) without touching the radius adjuster, so they are all exactly the same
4) Cut the pockets to fit the fills. You need accurate depth control to minimise leveling work. Start from the "bottom" working up to the overlaps. Glue in the blocks in the "bottom" layer and level before cutting the pockets for the next layer up
5) The ends of the pockets that are squared are trimmed by hand with a chisel
6) Think carefully about the glue you use where you have to route over a boundary multiple times. Titebond, for example, will tend to melt and wrap around a small bit, which then won't leave a sharp, well defined edge to your block. CA can stain and cause colours to run.
7) Build and level the layers successively until you've finished
8) When leveling be very aware of the changing grain angles when planing. Final leveling is with a hard backed sanding block (required for the shell).
9) As the work tends to be done over multiple days you need good humidity control, or you might find things go out of round

All this is high risk. If you make a mistake on the rosette you may need another top. If you damage the top in another way later, you can't save the rosette

Good luck and have fun!

_________________
Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Much appreciated Trevor, thank you.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Check out Dundee Luthiery on Facebook. He just posted a nice jig for cutting radial lines for a rosette.
https://www.facebook.com/dundeeluthiery
Kent

Nice design, but there is a reason for a rosette to be continuous around the hole, to keep cracks from happening in the top. It's not just a decorative detail.

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

You could always add one on the underneath side.

Pat

_________________
Pat

I've use a thinner top than most and laminate a spruce backer inside around the sound hole anyway.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

_________________
Mike Collins