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View Full Version : Video of installing purflings to an elliptical rosette.



Allen
12-26-2016, 05:17 PM
I've done 6 of these tenor soundboards the last few days, so thought I might shoot a little video to help demonstrate the process.

I always install the tiles first and let the glue dry. Then rout the purfling lines afterwards. Makes for a far cleaner and easier install when you have something this complicated.

What you don't see is that once they are all in place I flood the area with hot hide glue and work it in by running a veneer hammer over the area. Wipe up excess glue and let dry. Finally cut out sound hole.


https://youtu.be/tXtyaIfvWic

sequoia
12-26-2016, 06:01 PM
Thanks Allen. But what I would like to see is how you cut the eccentric channels on the elliptical rosette to begin with. This has always been a head scratcher to me. I have never been able to figure how it is done with conventional equipment. Ellipses are such a strange shape. However I love the look.

Allen
12-26-2016, 06:16 PM
No worries at all when you spend 5 years learning 3D CAD/CAM and then designing and building a big CNC router for in the workshop that was over a year in the making. Then spending a bomb on a laser for in the office.

You could do the elliptical ones with guide bushings and templates to route to. Or a pin router and templates. Far too much work and difficulty to get them spot on for me to have ever wanted to try it.

My previous round sound holes and rosettes were an evolution from the dremel and Stewmac base, through to a conventional knee milling machine set up on a pin in the centre of the sound hole. Lot's of work and painstaking setup. About a day to do one rosette, where now I can do one in 1/2 hour not including some dry time for the glue.

sequoia
12-26-2016, 07:01 PM
My previous round sound holes and rosettes were an evolution from the dremel and Stewmac base,

That is where I'm at Allen. Perhaps someday I will graduate to the ellipse. I do like a challenge, but that challenge still eludes me. The CAD/CAM route is obviously the way to go, but I'm getting old and slow. ... However, the famous Selmer guitar maker in 1930s produced an eccentric sound hole guitar with matching rosettes before CAD/CAM and I have always been puzzled about how they did it. I suspect they were hand cut from templates, but don't know. Anyway, they proved it could be done before CAD/CAM.

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Allen
12-26-2016, 08:16 PM
When you have time on your side, you can do an awful lot with a template and sharp tools.

Dan Gleibitz
12-27-2016, 12:04 AM
Brilliant. Thanks for sharing (finally I can sleep at night - seriously, trying to figure this out was bugging me).

The amount of effort that is involved in creating this type of fine work with a CNC machine must be considerable. I quickly learnt it's not just design then CAD then press print; there's an art to even holding the work piece, especially a thin one like this, in a way that can be repeated. Even more difficult with multiple passes using different tools. I think I gleaned a clue or two from this video.

I've still not worked out how you deal with the square corners though. By hand?

Timbuck
12-27-2016, 03:05 AM
Neat stuff Allen ...How are you locating the top to the work board ? to get the correct indexing to rout out the purfling channel and sound hole when you return it back to the CNC router..are you using double sided tape and indexing pins ?

Allen
12-27-2016, 09:00 AM
It's fixed to a work board with double sided tape and it stays there for the entire process.

Removing and replacing could be done with indexing pins and vacuum, but more trouble than it's worth for something like this that needs absolutely perfect alignment. Plus I priced out a vacuum pump that was capable of doing this sort of work, and the price will take your breath away.

Square corners are a bit of an illusion. If you clean up with a contour pass using a very small diameter cutter such as a 1.0mm bit, then the radius in the corners is just 0.5mm.

Kevin Waldron
12-27-2016, 01:56 PM
Allen,

It really want take as much vacuum as you think...... should be able to find used vacuum pumps even down under (look at some of the Gast pumps)....... check this video out for a lot of ideas. Even Venturi will do what your needing to do. You might want to consider gasket mask......

https://video.search.yahoo.com/yhs/search?fr=yhs-mozilla-002&hsimp=yhs-002&hspart=mozilla&p=youtube+fixturing+with+router+bog#id=1&vid=7bd9a63a36e8c7952c7cc0ffa8457466&action=click

http://www.joewoodworker.com/

Thought..... have you ever considered making an aluminum template/jig/fixture for pre-gluing all of this at one time thicker and slicing out what you need for more than one at a time? The fact that you have space between the elliptical pieces would lend itself to doing so. You might also consider gluing all of this up on a newspaper in reverse with proper fixture and placing..... glue releases with heat.

For those asking about manual ellipses .....several years back we also designed some hand cut templates using a bearing guide.... you can use this idea and go further.

Just some thoughts.

kw

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