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PostPosted: Fri Feb 07, 2020 10:08 am 
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I've seen questions about glue and bindings lately on the forum. My latest build seemed like a good time to show everyone how I use CA glue when doing binding purfling. This is going to be old hat to most folks, but we have some new people to the forum who might like the information.

First and foremost, you HAVE to prepare your channels. Although you may have used a jig or even an expensive binder, they have to be further cleaned and refined, or your bindings and purflings won't fit well.

This is one area where new folks don't necessarily know to give a lot of attention. It takes 10 minutes to rout the channels. Expect to spend an hour or two refining those channels. With small pieces of your purfling and binding, check every inch of the channels for fit. Clean them out, in some places they'll need to be deeper or more even. In some places the angle might need to be refined. This is part of the fit and finish that you hear so much about. This is an area where you can tell an amateur guitar from a professional. It's a learning curve guys and in some areas it takes experience to learn what needs to be done and how. This is one of those Achilles heel areas.

I don't use CA glue for every build. I prefer Duco Cement for most. For this build, I'm using PVC b/w/b purfling and ivoroid, so they lend themselves well to CA glue. Although the herringbone is a wood fiber product, I also used CA glue for the herringbone purfling. For the rosette, I used Duco.

A word of caution for those of you new to luthiery. CA Glue does NOT get along with all woods, spruce being one of them. CA glue will discolor spruce a nasty yellow, if you don't seal the grain! Also, DON'T USE CA GLUE DIRECTLY ON MAHOGANY OR MAPLE. It discolors these woods too.

You can use CA glue for bindings and purfling, but you MUST seal the grain on all spruce, mahogany, maple (and perhaps other woods). I simply seal them all with shellac. You can use other finishes as well. I like shellac because it plays well with others. You can use shellac under any water based or oil based finish, at least those I've tried such as, shellac (of course), polyurethane, nitrocellulose, lacquer, and TruOil.

After routing all of the purfling and binding channels, I apply a generous amount of shellac to the channels. You don't have to do the entire guitar; you need to seal those cut channels. I do this 2 or 3 times. Look closely and make absolutely sure that ALL of the channel is sealed, including the back corners, where the walls come together. On the end grain, at the top and bottom of the box, it's easy to miss little tiny areas, leaving wood fibers dry. This is why you want to apply it a second, or even 3rd time.

More experienced luthiers can control the top purfling, binding, and side purfling (if used) all at the same time. I can't. So, I do my gluings in 2 phases when I do side purfling.

In the case of this guitar, the herringbone is wide and prebent. It didn't fit perfectly in the channel, so I needed to shape and tape it so that it would fit tightly although it had spring back. It's harder to work with than regular purfling, so I did this as a separate gluing. The back of the box has b/w/b top and side purfling with ivoroid. Also, since I'm doing side purfling, I did the top purfling as a separate gluing.

The photos are only of the top ivoroid and side purfling, which I did together. I did the same procedures on the back as the top.

After sealing the channels with shellac, I taped my herringbone into place, using 3M 233+ tape. It has just the right amount of stretch. Plus I've found it stronger but easier to remove than masking tape or painter's blue tape. After I had the herringbone in place, using a pipette that I stretched so make a micro pipette, I used THIN ca glue along the top and side, between the tape. The glue is thin. It leeches under the tape and into the crevices.

1 hour later, I can remove the tape, checking that everything is glued. If you see a small area that didn't get the glue, glue it now and tape it.

Next, although I've prepared my channels, I double check the fit of my binding and side purfling after the top purfling has been glued. I had to tweak a couple of places to ensure a tight fit. After I'm happy with the fit, I tape my binding and side purfling into place. Using the thin ca glue and micro pipetter, I glue along the top seam, where the binding and purfling meet, then along the purfling/binding on the side.

1 hour later, I remove the tape and check that everything is glued. I found a small area that needed glue. I applied the glue and taped.

Done

(YES, I have small dirty MAN HANDS, a byproduct of luthiery!)

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PostPosted: Fri Feb 07, 2020 11:47 am 
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Joined: Mon Jul 09, 2012 9:49 pm
Posts: 278
What a wonderful tutorial. Thanks very much. Nice to see a discussion of where patience and rework is routinely required. And the warnings about CA.

I've used CA for coming up on 40 years, and of all the adhesives we use, that one can cause the most trouble if allowed to. Most folks don't understand how tight joints need to be and how little CA is needed to do the attaching.

Thanks again!

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PostPosted: Fri Feb 07, 2020 12:30 pm 
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Joined: Sun Mar 09, 2014 8:13 pm
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You're very welcome Peter. Thank you for your kind comments.


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PostPosted: Fri Feb 07, 2020 4:12 pm 
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Joined: Sat Mar 24, 2018 5:41 pm
Posts: 53
Location: Durham, NC
I agree Peter! An excellent tutorial!

I would like to ask what tools Diane uses to clean up or rework the channels after the initial ledge is routed?
I've seen a friend use a file that has been bent into an arc so it is easy to get into the bends in the ledge, but I often wonder if there are other clever ideas out there.

Also, what kind of clearance do you shoot for when comparing the heights of the purfling or binding when compared to the surrounding wood. Is the wood slightly proud so it can be sanded without thinning the binding? Or, do you attempt to make the two exactly equal?

Thanks again Diane.

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PostPosted: Fri Feb 07, 2020 4:30 pm 
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Rex, there are sets of curved files available inexpensively, sold as 'riffler' files. Maybe these will be useful.

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PostPosted: Fri Feb 07, 2020 4:41 pm 
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Joined: Fri Mar 03, 2006 7:09 pm
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Location: Hegins, Pa
nice work

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Blues Creek Guitars Inc
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president of Association of Stringed Instrument Artisans
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PostPosted: Fri Feb 07, 2020 7:05 pm 
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Joined: Thu May 24, 2012 8:03 am
Posts: 1212
Location: Chestertown Maryland
Rex

find a small file with "safe" edges, edges that have no teeth. A 6-8" version is a good size, a finer cut tooth gives a finer finish

https://www.jensentools.com/nicholson-06601n-06601-cooper-8-file-cut-safe-edge-carded/p/172-086

That way you can file just the side or just the bottom at a time. And if the file has a straight edge, it does a good job of flattening the bottom of the chanel. The only place a flat file won't work is at the waste, so for that you will need a small riffler file like this:

https://contenti.com/913-die-sinkers-riffler-files

They come in all shapes, but the large flat area on this one makes it easy

Here are mine - click to enlarge to see the safe edge


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PostPosted: Fri Feb 07, 2020 7:15 pm 
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Here's the razor file that I use. I got mine from Woodcraft. They're made by Iwaski. It has a safety edge on each side. They make many shapes and sizes.

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PostPosted: Sun Feb 09, 2020 12:37 pm 
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Joined: Sat Nov 13, 2010 9:55 pm
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Location: Pittsburgh PA suburbs
Thanks, Diane,

Thanks for explaining about the cleanup and sealing prep. Hopefully that helps me out of my current pickle. I may end up just using duco in the end, but I'm still hoping to try out thin CA next time.

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PostPosted: Tue Feb 11, 2020 8:38 am 
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Joined: Thu May 24, 2012 8:03 am
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Location: Chestertown Maryland
I tried CA on one and did my usual taping with lots of pieces of tape. The clean up was very tedious. On the next couple I experimented and found I could getaway with much less tape, and also applying glue to the portions between the tape, pulling the tape and finishing the glue

Check this shot and the 5-6 to the right of it

https://www.flickr.com/photos/ruby1638/42682176221/in/album-72157688488198220/

Ed


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