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I am doing another segmented rosette I thought I would share my first time every time seamless box miter process and a couple of my Top Secret Weapons.



Pretty obvious how I got to this point (forming the segment that the Box miter will go around)



Then roll out my Top Secret Weapon #1. A simply fabricated fixture to pre-size and miter the purfling for the box miter.




Operation of this secret weapon is simple. Insert the purfling into the channels, and chisel your miters.



With very little effort I have the five pieces required for one segment of the 12 segment rosette i am building.


Now for Top Secret Weapon #2. A simple channel to the appropriate size of the box mitered segment routed in UHMW.

A word to the wise here. You want this to be an exact fit. Not at all loose or at all tight. Kind of the three bears just right kind of fit.



Insert the pieces and carefully and align the miter edges.

Notice the inside purfling is perfectly in place the outside piece is shifted a fraction to the right. This must be fitted in the exact position prior to glue-up to achieve a near seamless joint with the end pieces. I did not notice till after the picture was taken, but positioned it properly prior to gluing in place.

I find it works better to insert the 2 long sections and glue in place with thin CA using a fine capillary nozzle before doing the same on the end pieces.

It take very-very little CA to secure the purfling to the wood. excess CA will seep on to the miters and make it hard to fit up the end pieces so take care to use just a drop of CA in three place slightly away from where the end pieces will touch. When you glue up the end pieces you can then be a tad bit more liberal with the CA. But here again not much is needed.


And now the final product. Well not quite the final product but the first box mitered segment for this rosette. Just 11 more to go. Well actually 24 since I am building two guitars that will use this rosette.

I think this is a pretty efficient process and produces nice seamless box miters. Once3 you have built the fixtures and have gone through the glue-up process a couple times. You can crank out 12 segments in under a half hour. Try to fit 48 miters in half an hour I can do it!! with the hep of My Top Secret Weapons

Really nice tutorial, Michael!! Thanks.

Ron

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OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

Do you have a picture of the finished rosette?

                      Thanks, Red

Good stuff. I'm totally gonna steal your ideas, Thanks

Not yet! I am making these segment up in advance. I will join the top this weekend. as soon as the rosette is inlaid I will post the picture but it is something like this one

Awesome Sir, thanks greatly for the time it took to do all that for us. Very clever!

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Eagles may soar, but weasels don't get sucked into jet engines.

Thanks for sharing that.

Thanks Michael,

Is this going into the tutorial archive?   

Why did you shift the outer purfling to the right? Do you trim the wood segment to fit?

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Horton, MI

Mike,
How do you set the angle of the notches in the first jig. They aren't 90 degrees.

[QUOTE=Kirt] Thanks Michael,

Is this going into the tutorial archive?   

Why did you shift the outer purfling to the right? Do you trim the wood segment to fit?[/QUOTE]

I did not mean to. I stuck the parts in the UHMW fixture and aligned but missed on the outside purfling.

I had to properly aligned before I glued up. I just did not notice the misalignment till after I took the photo. So I decided to use this as an instructional exercise to highlight that a minor misalignment like this will cause problems when glue the side pieces on.

That's great! Thanks for sharing. I really like that rosette...

One of these days, my secret weapon is gonna be a cnc...

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"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

Oh, I see, it was a boo boo.

Guess I need another cup of coffee. I'll catch on eventually.

Thanks again.

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Horton, MI

Good job, Michael!  Good jig design too.  Makes the required precision easier.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

To answer your question on trimming the wood. I do not trim as I go. every as far as the box miter and the whole rosette for that mater is dependent on every piece being within an acceptable manufacturing tolerance pre-glue up.

The Rosette is designed on cad and templates are made to fabricate the parts around to in sure they fit.

The Rosette design

The fixture templates

The wood segmentation template

Thanks Michael, It looks like so much work, but so worth it!
And your templates make it mucho quicker.
It looks just awesome! One of the nicest I've seen.

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Anderson Guitars
Clearwater,Fl. 33755

Mike I plan it all out on cad. You are right. The angles are different at the inside piece and outside piece due to the taper of the pie segment. the combined angle on this segment is pretty close to 90 deg. 89.889 but like I said I make fabrication templates on clear mylar with very thin line weights and glue the templates to the wood stock and use a very sharp razor knife to cut out the parts for the fixtures and use a rosette jig to cut the channels.

Mike Mahar brought up a good point. Because the purfing is wrapped around a pie segment the angle of the miter is not 45degs at each corner. The required angle is different at the outer purfling and the inner purfling. This angle will change depending on how many segments the pie is divided into. Here is the layout for a 12 segment rosette

[QUOTE=Kirt] Thanks Michael,

Is this going into the tutorial archive?   

Why did you shift the outer purfling to the right? Do you trim the wood segment to fit?[/QUOTE]

I put it in the archive as soon as I saw it. Fantastic tutorial. I'll be making up a jig for this today. Thanks Michael.

Cheers

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Bob Connor
Geelong, Australia

[QUOTE=MichaelP] Mike Mahar brought up a good point. Because the purfing is wrapped around a pie segment the angle of the miter is not 45degs at each corner. The required angle is different at the outer purfling and the inner purfling. This angle will change depending on how many segments the pie is divided into. [/QUOTE]

So you have to make sure that one of the short pieces is placed in the small triangle top side up and the other is top side down. With the angles so close to 90 degrees it either doesn't matter or you get a poor fit that off by just a small amount.

you just flip the short piece over to the other side (not rotate but flip face side up to face side down.). It is easy to notice if you get it wrong the is a miss fit at the white laminate if you don't flip it over for the opposite side.

If your perfling is symetrical B/W/B you can flip it when you place glue it to the other pieces. If the perfling is asymetrical, B/W/R you have to flip it when you put it into the trimming jig. right?

If it was BWR with the red to out side and you fliped faces the red would still be to the out side. Take a strip of trasparent paper cut to the shape and draw three lines. label each section with a leter. when you flip the facethat is up to the down side nether the angels position nor does the colors change position the red is still to the out side. the end pieces are exact mirror images of each other. Quoting Pepeye here "me's thinks you are trying to out think your self here".

Because it goes on the opposite side of the segment flipping faces will always keep the colors and angles in the proper place. No mater what the color combo is.

I should also have said rotating the short pieces instead of flipping faces, will still keep the colors in the right place but will change the miter angles position. The miter angle on the right side or bottom depending how you are looking at the segment would then be at the left or top. and therefore not match the miter angles on the long pieces. you have to flip faces. no need to worry with this when you use the fixture. It is only relative when you get ready to glue up.