Official Luthiers Forum!

The binding job on the edge of the sound hole on my current build didn't turn out so well. See pics. (Curiously this is the second time I have used binding on the edge of the sound hole and the first time went much better.) I used cocobolo binding with two thin BWBW purfling strips. I bent the coco by itself first then glued the purfling to the coco with Titebond, then glued it all up to the sound hole edge with Titebond using binding tape. The binding wasn't formed to fit exactly to the sound hole but I thought it was close enough and I could pull it in place with binding tape. I was wrong, and left several gaps which I filled with black CA glue. The final results are less than desirable and I will rout it out and start over. I would appreciate any advice on how to proceed to get it perfect, or at least near perfect results.

When I or my students have wanted a bound edge on the soundhole, we didnt bind it so much as inlay it ..... what i do is leave the top thick when doing this. Route a trough the size of the binding and purfling as required, not all the way thru, but deep enough that when you thickness the top to final thickness, the bottom of the trough will be sanded off. Now inlay the edging, and then clean up the top side with a plane or in the sander. Now inlay your rosette if you are doing one. Then once thats all cleaned up, thin the top from the backside, and the soundhole will have its binding on it ... all this gets done with CA - the trick as always with rosettes and such is to have the bindings. purflings fit the trough snug . then glue in with CA.

This is off course for round rosettes .... could also be done with ovals if you have templates or do it with a CNC ...

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

It looks like you are doing that with two pieces, that is going to be tough to get fit well. I'd do it with one big loop and bend it on an iron first to get it to be shaped real close. Then miter off one end true to the center line and follow with small shavings off the other until you have a force fit dry where you are slipping the joint in place. Then glue it and force the joint together. The addition of the moisture from the tightbond should help expand and hold it in place.

An alternative is to do it as you are doing with two pieces. Make the miter at the point joint to fit true.Then cut the other end of one at a 45 degree angle with the open side of the angle in towards the center. Slowly shave off the other till you have a force fit that is just a shade long making a lap joint. This will be harder to get a force fit, you might have to make some spring expander sticks to help hold it out against the top wood as well as taping.

Just some thoughts,
Alan D.

Thanks Tony and dunwell. Great ideas. Anyone else?

Hi Goodin

I am working on a guitar that I wanted a bound soundhole on and came up with an idea to inlay it rather than bind it. I think this would be similiar to Tony's method. I am doing a round soundhole, but I think with the proper jigs you could do one of any shape - it would be more work than a round one and maybe be a little easier to make a mistake. I don't want to hi-jack your thread so I'm including one picture of the unfinished top and would be happy to explain the method I used if you are interested - Mike

_________________
guitarsbygiltzow.com

Tony - do you seal the channel before installing the binding/purfling to prevent staining the spruce? If so, what do you use? Thanks.

Hi Michael - I like yours and Tonys inlay idea. Seems like that would work great for a round sound hole. I will keep that in mind for future builds. I don't think this will work for my current situation as the hole is already cut and soundboard sanded to final thickness. I will have to do the binding method. I have thought about it some more and I think a lot of my problem is the cocobolo binding I'm using. It's so stiff that it won't give enough to form to the edge. I'm thinking I will thin it by about 30% so it has more flexibility and try to bend it more closely to the sound hole shape.

Hey Alan, what are spring expander sticks?

Thanks guys.

For your situation with an irregular hole I have a couple of solutions.

1- Bind the soundhole with the cocobolo as best you can without the purfling. Make the cocobolo a little thicker than you want. Then rout out a channel for the purfling and inlay it. It might not look so perfect from the back but you can inlay that too if you like.

2- You can laminate two thinner pieces of cocobolo instead of one piece for the binding. It will be easier to conform to the shape of the soundhole when you tape it up with the purfling. After it's glued together you won't see that the binding is not one piece.

A couple of other tips. You can reverse the heads on one of those small Irwin clamps and use it to spread the binding in place as you CA it. Work your way around the hole making sure to keep the CA behind the clamped part. Let it set up before you move on. I do this without tape. I can hold it up to the light and see if there are any spaces between the binding and the soundhole and clamp it there. If you do use tape use thin strips and tack the binding in between the strips with the CA. Tape works fine when the binding is thin but not so well when it's thicker than 1/16".

_________________
Ken Franklin
clumsy yet persistent
https://www.kenfranklinukulele.com

Ken - Excellent ideas...Couple questions:

1- How do I go about routing a channel for purfling on an irregular sound hole after the binding is already installed?

2- I like this idea the best so far. It would require fitting joints at the binding ends twice, but I think I can make it look ok.

I am used to using Titebond for this procedure. How do you go about using CA? Small sections at a time?

Robbie O'Brien has a vid segment on where he binds a sound-hole. Hopefully he'll chime in.

-Steve

Don't forget that baloons make great devices for exerting even pressure on the binding. Though that angled part might make it harder to do.

1- You make a template and use router template guide bushings. You cut out the hole with one size bushing and then cut the purfling slot with another. There will be some hand work with small chisels on the pointy part.

2- With CA you have to shellac the top first so the CA won't sink into and discolor the wood. Then you start at one end and glue a small section at a time. Wait to make sure the glue doesn't get ahead of the reversed clamp if you are using it as a spreader. When you have about 3" left to do you can fit the ends and finish gluing.

If you are not using a spreader clamp but are taping it all at once, cut your tape in half lengthwise and only leave about 1/4" space between each piece of tape. Then you can put a dot of super thin CA in each space between the tape. Take the tape off and fill in the rest with CA.

_________________
Ken Franklin
clumsy yet persistent
https://www.kenfranklinukulele.com

As Ken mentions above, you need to shellac the top and the channels prior to gluing .. I use LV bottled french polish (padding lacquer) .. it works great and is always ready to go

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"