Bending Bindings - Luthier Tips du Jour Mailbag
In this episode, Robbie O’Brien answers a viewer’s question about how to bend bindings without damaging the purfling glued to them.
Video Transcription
[on-screen text reads: Luthier Tips du Jour Mailbag]
Mailbag question: How do you bend bindings without damaging the purfling line?
Robert O'Brien: Today's Tips du Jour Mailbag question comes to us from California. "Dear Robert, can you offer any advice on how to bend bindings without damaging the purfling line glued to the bottom of it? Thanks for your videos, Chris, in California."
Okay, just a quick explanation for those that are not familiar with this issue. Here's the bindings. On the bindings, these are rosewood bindings I got from LMI, on the bottom of it is a white maple purfling line that is glued to it. This really offsets the binding from the side when it comes time to install them. It looks really nice.
However, when you're bending these under the heat and the moisture and the stress of the actual bend, sometimes you could damage that little white purfling line. It either gets wrinkled or starts to delaminate, and in extreme cases, you can actually burn it. The technical term for that is bad.
Use a glue with high resistance to moisture and temperature
There are a couple of things you can do to keep this from happening when bending. First of all, when you make your bindings, if you decide to make your bindings, use a glue that has a little higher resistance to moisture and temperature. When I make my own bindings, I use either Titebond II or Titebond III for this very reason. The Titebond II and the Titebond III can withstand higher temperatures and higher moisture content. And we have both of these when we're bending the bindings.
Tightly tape the bindings together
Now, there are a couple of other things you can do as well. First of all, if you have a purfling strip on there, you want to put those two together. That way, when you bend them, you've got a top and a bottom for a right and a left side. If you bend them this way, you may not have the configuration that you want as far as left and right and top and bottom. So, always put them together like this. Now, this also helps keep that purfling line attached when you're bending. For example, what I like to do is just take a piece of tape and just put them tightly together, and wrap a piece of tape around there. I'll do that on each end and a little bit off of the waste because you don't want to get that tape really hot. Sometimes, it's hard to peel off of there afterwards.
Another thing you can do is just take your tape and just spiral it all the way down the binding and really hold those things tightly together. That helps support the purfling line. I've also seen guys come in with some light twine or string and wrap it up, and you don't have the problem of trying to get the tape that's been heated, get that adhesive back off the binding. So you can just wrap it in light twine or string, and that also works.
Keep binding thickness just above 2 millimeters
Once that's done, you're ready to bend. Now, let me back up just a second here and talk a little bit about the thickness of the bindings. I like to keep my bindings somewhere around a fat two millimeters, 2.05, 2.10. That's about as thick as I go on the bindings and the purfling line. That seems to help the binding of the purfling bend a little easier without breaking. Once you get above 2-1/2, go up into 2.83, then you got a little problem with the bending of the binding and having it break, and the purfling line wanting to crack or delaminate.
Keep the bender heat down
So, once I have them all taped together or wrapped with twine, now I'm ready to go to the bender. Once you bend, keep the heat down. You don't want to go above about 325, and you don't want to dilly-dally. That's a technical term. You want to get this thing bent with the least amount of heat and moisture possible. So Chris, in California, thank you very much for your question, and I hope, with this information, you're now able to bend your bindings without damaging the purfling line.
[on-screen text reads: More Luthier Tips and online courses available at www.obrienguitars.com. Private and small group guitar building and finishing instruction available.]
