|Ebony binding,Valleys Guitars, Australia|
BINDINGS AND PURFLING TIPS
by Chris Herrod
Installing binding and purfling on a guitar is one of the most intimidating of all procedures for the new builder, but with the proper tools and techniques, and careful preparation, there should be no need for concern. Some think that binding is simply decorative –a way to add an appealing frame to the woods used in a guitar. Although there is a very small minority of guitar makers who forego binding their instruments, most builders believe it is essential for sealing the endgrain and for protecting the edges of the instrument. Without binding, a bump on the edge of the instrument is much more likely to start a crack in the top or back.
The difference between bindings and purflings is simple. The bindings (sometimes called ‘banding’ ‘trim’ or ‘edge binding”) are seated at the outermost corner of the instrument, whereas purflings sit between the binding and top, back or side.
Unlike bindings, purflings are purely decorative. Typically you will only find binding and purfling installed around the top and the back, but some like to bind the fingerboard (this makes fret work more challenging) and the headstock. Purfling strips are also commonly used to create the black and/or white rings that appear inside and outside of the rosette.
Bindings can be made from wood, plastic or fiber. Wood bindings are found on most high-end and custom instruments, but plastic bindings are common and are a traditional component of many well-loved factory models. Most Martin guitars, for example, have plastic binding. Common wood choices for binding are Ebony, Rosewood (LMI carries several species of Rosewood binding), Maple and Koa. Figured binding wood (i.e. Flamed Maple or Flamed Koa) and other more exotic choices such as Pernambuco and Snakewood, are sometimes used on special instruments. Plastic bindings are available in simple black or white strips or in various combinations of blank and white, glued up in layers. Wood bindings need to be bent using heat (much like sides are bent) but plastic bindings are flexible and do not need to be bent with heat.
There are far more choices available for purflings, the simplest being a maple or “ebonized” (dyed black) wood strip which is used to separate like colored bindings and woods. For example, a dark Ebony binding can be set apart from some dark Rosewood sides with a thin white Maple purfling line.
Black and white purflings can be made of wood, plastic or fiber. Fiber is a wood product that has the consistency of hard paper and is more boldly colored than pure wood strips. LMI offers a wide variety of wood and fiber purflings in various sizes and combinations of black and white. We also carry fiber veneer sheets from which you can make your own combinations. Colored veneers are often cut into strips and used as purfling (see illustration #2, photo). LMI carries a wide variety of colored veneers for this purpose.
Additionally, there is a whole other class of purflings, called marquetry purflings. These are made from intricately combined pieces of veneer to form a decorative pattern. The ‘herringbone’ pattern is the most familiar (the two on the left below, fine and bold) but there are many more to choose from. Few luthiers make their own marquetry purflings as the process is difficult, time consuming and normally a large number of a single purfling design must be made at one time. For this reason, marquetry purflings are usually selected by luthiers from the options available from LMI and other supply houses.
Finally there is shell purfling. Individual pieces of (hard) mother of pearl or abalone are inlayed into a channel adjacent to the binding. It is not easy to do, but when it is done well, the effect is stunning .
5 major steps (and numerous smaller ones!) to the successful installation of binding and purfling on your instrument:
- Design your binding and purfling motif and make drawings and measurements. Then, select and purchase the appropriate materials. Make sure that you have the right sized router cutter and bearings also (you can order all these goods from LMI). If you are doing a shell purfling, be sure to get the appropriately sized Teflon strips to help you install the shell.
- Prepare the binding and purfling for installation.
- Set up your router with the proper cutter and bearing and cut a test channel in some scrap wood, then rout the channels into the instrument.
- Glue the binding and purfling onto the instrument.
- After the glue has dried, scrape or sand the binding and purfling flush to the surfaces of the instrument.
Designing your Binding and Purfling Motif
What you select for binding and purfling on your instrument does little to affect the structure or sound of it, so your decisions will be based primarily on aesthetics. However, there are some mistakes you want to avoid. Steer clear of putting like colored pieces together. For instance, you do not want to lay a piece of black fiber purfling against a dark Wenge back and you do not want to set white binding against a light colored maple back. Avoid clashing colors. A purple purfling line might not be a good choice beside an orange-ish Padauk back, for example. Make sure that the bindings and purflings you select are consistent throughout the whole instrument. It is not advisable to use widely different motifs for the back and for the top, etc.
Once you have a motif in mind, make a drawing and measure everything carefully. Now make, select or buy the binding and purfling strips you will use. Make sure the bindings and purflings you choose are long enough for your instrument, bearing in mind that most strips sold by LMI and others are not long enough to go all the way around the instrument and must be joined at the end (more on this later!). Also, remember that once your bindings are installed that you will be scraping them down flush to the body, so make sure you have enough material for this. These considerations will help you select the proper bearings for your router (preparing the binding and purfling channel using hand tools will also be covered below). For instance, if you are using a binding that is .060 thick, you will not want to rout a .060 channel. Rout the channel to .055 +/-, so that the binding protrudes a bit. Remember also that wood parts will absorb glue, so your glue will add .001 or .002 to the final dimension.
Preparing shell materials for purfling is exacting work. Often we here at LMI are asked how many straight and how many curved strips are needed to go around the edge of a particular instrument. There is no set answer for this as different luthiers have different methods for this work, but in general, it is usually a proportion of 2/3 straight strips to 1/3 curved strips. It usually takes about 70" to do one edge on a guitar body, about 290" to do a complete D-45-style guitar and soundholes use about 15". The curvature of the instrument has a lot to do with how much shell you will need. It is always best to order extra pieces if you are not sure (unused and unworked pieces can be returned to LMI for credit within 30 days). This will allow you to more closely color-match your sets as well.
If care is taken to color-match adjoining ends, joints between shell pieces will be almost invisible. Another effect is to gradually “fade” from one color to another, or even set up a “pulsing” rhythm by going from light to dark to light. On soft curves, around a guitar body for instance, straight pieces can be laid into a glue-filled channel and then forced to break into several pieces to conform to the curve. The breaks will be all but invisible in abalone.
Preparing the Bindings and Purflings
Besides trimming the strips to length you also want to make sure that the edge of the strip that will sit at the bottom of the channel is completely flat and smooth. Any gaps or saw marks will leave unsightly glue filled gaps. Most bindings sold by LMI are jointed on one edge, but it is best to go over each piece carefully to make sure it is smooth. If additional work needs to be done to the binding, or if you have sawn your own binding strips, then hold a flat, coarse file in a vice and run the edge against the file with an even stroke to flatten it. Use a bandsaw to cut bindings down to a lower height if necessary.
If you are using wooden binding, the binding will have to be bent prior to installation. This can be done by hand over a hot pipe (SPBTN, SPBT or SPBPS) or on one of LMI’s side bending machines. The bending machine provides the greatest support for the strips as you heat the wood, so you will have the best chance of successful bending without breaking, plus you can bend all four binding strips at once. But for many, the traditional hot pipe method works fine. If you are using the SPBPS Electric Free-Form Bending Iron you can get the guide bands (SPBPSB) which create a narrow trough for the wood strips. Using the bands adds support, which makes it easier to create a straight and even bend. The bands can also help to hold together laminated bindings during the bending process.
Some woods are more difficult to bend, such as Ebony (because of its denseness) and figured woods, like curly Koa and Maple. With these woods, it is best to bring the thickness of the strips down as far as possible -and use some extra heat in order to make the bending go well. It’s not a bad idea to purchase an extra strip if you are using one of these woods, just in case you break one. You can, of course, order pre-bent bindings from LMI, if you wish. Select binding strips from any of the many woods we carry and then select the binding bending service for the body shape of your guitar. We bend to many popular guitar body shapes.Plastic bindings and fiber purflings do not usually need to be pre-bent, but you might want to soften some plastics with a hair dryer (using light heat!) for tight bends –around a cutaway, for example. Some woods, such as Cocobolo and Indian rosewood, are oily and so it is a good idea to wipe them down with Acetone just prior to glue up. Make sure you let the acetone fully evaporate before gluing.
Routing the Binding and Purfling Channels
Safety: Your safety is important to us. Woodworking can at times be a dangerous endeavor, so learning the proper use of tools, glues and finishing products is important for your safety. This is especially true for powered routers. LMI assumes that our customers have taken the time to learn proper woodworking safety practices on their own and have read their tool’s manuals carefully and completely.
The most common tool for creating the channel around the edge of your guitar is the router. A full-sized router will supply ample power, but a laminate trimmer is more than adequate, is lighter in weight and easier to maneuver. You can use a dremel tool, but most builders consider it under-powered (plus in many models the bearings are not sufficiently tight, which many create an uneven channel). The Black and Decker wizard is a better choice in small routers. If you do elect to use the Wizard or Dremel, you will want to rout the channel in a series of passes, taking just a bit of wood off with each pass.
Hand tools can be used if you wish, but they require considerable skill to get good results. Use a gramil (SPG, see below) to score the edge of the channel on the top or back plate –and along the sides. Then use a sharp chisel to remove the material making sure that the channel is square and smooth. If you choose to use hand tools, be sure to practice on scrap, several times, before attempting to create the channel on your guitar.
For many common purfling/binding combinations, you will need to create two ledges. The top channel for the purfling is routed first and the binding channel (the deeper of the two) is routed second. Be sure to rout some test ledges in scrap wood to make sure that your binding and purfling fit perfectly. Using the exact sequence on your test piece as you will use on the guitar so that there are no differences between your test and the instrument. First, if you haven’t already, make sure that the top and back plates are flush with the sides (a flush trim bit works well for this).
Now, score the edges of the channel using the gramil (SPG) or a similar device. Be sure to take care to set up the gramil so that the score line frames the outside of the channel perfectly. Many builders skip straight to routing, but the gramil helps tremendously to avoid tear-out, assuring a clean sharp edge. Make sure your gramil blade is sharp, that you do not cut too deep and be sure to use it on your test piece. Another way to help avoid tear-out is coat the top wood with a coat of shellac before routing.
Most steel sting guitars, all archtop guitars and many classicals and electrics have an arched or curved top and/or back plate, meaning the angle between the plate and the sides is going to be slightly obtuse. You will need to account for the arch of the top and back plates so that the binding channel you rout is parallel with the sides. There are two main ways to do this. The first is to attach a wedge to the base of the router so that the bit is parallel with the sides as the router base moves along the arched top or back plate.
Some commercially available router bases have the means to do this but for most it requires adding a wooden wedge to the base plate. One of the disadvantages of this approach is that the arch on most guitars varies slightly around different areas of the guitar. So you may need to remove or adjust the wedge at different parts of the channel.
The other way is to hold the router in a carriage that moves up and down, perpendicular to the work table and parallel to the sides. LMI’s Professional Binding Machine (BM2) is such a tool.
There are other tools that builders use that are based on the same principle. This tool is very popular because you can create a binding channel that is perfectly positioned vis a vis the sides without having to readjust the tool. It conforms to different arches on a single guitar and can be used on differently designed instruments.
You have already designed and measured your bindings, purflings and their corresponding channels, and you have selected the appropriate bearings in the step above (#1). Now, set up your router with the cutter and bearings that you will use to rout the first channel (usually the purfling channel or ledge). The width of this channel will be the sum of the binding and purfling (minus a few thousandths) and the depth of the purfling (minus a few thousandths). Firmly clamp the guitar in such a way so that the top is as parallel to the work surface as possible. The Ribbecke binding Machine comes with a carriage for holding the guitar in this way. Regardless of the method you choose, the guitar should be stable.
In order to avoid tear out, refrain from moving the router too quickly. Hold the router firmly and move in a clockwise fashion so that the cutters move into the work. Some builders do a second pass counter-clockwise to clean up, but by doing this you run the risk of the cutters grabbing into the wood –sending the router out over the top of the guitar!
After you have completed your first pass with the router, quickly check the channels one more time with the binding and purfling strips to make sure they will fit properly, then proceed with the rest. On some guitars, the binding channel is routed while the neck is attached to the body (such as classical guitars built in the Spanish tradition). Because you will not be able to rout the channels clean up to the neck, you will need to carefully remove wood with a sharp chisel from this area. On guitars with a dovetail joint, you will not be able to run your bearings near the mortise and will need to use a chisel for the binding/purfling channel here as well.
Installing the Binding and Purfling
There are a number of different ways to “clamp” the binding and purfling to the guitar as you glue it. We will explain here the easiest and most common method. There are additional concerns for elaborate trim designs (on and around the heel cap, headstock, and on cutaway instruments) that will not be covered here. We will take only a cursory glance at the techniques for installing shell purfling.
Now that the channels are cut and the bindings are prepared, it is time to bring the two together. First make sure that the ends of the bindings meet at the center point at the butt of the guitar –but leave them a little long. Use FT75 binding tape at a few points for a dry run as you prepare the ends of the strips. Carefully nibble away at the ends until you get a seamless butt-joint (some prefer a scarf joint here). For this, it is important that the binding is trimmed square. Usually this is done with a sharp chisel cutting perpendicular to the length of the strip onto a piece of hardboard. Make sure the bindings are cut flush at the neck in this way also. Once you are sure that the binding is seated properly, remove the tape. Be careful to pull the tape away from the top wood at an angle. Do not pull it straight up or you may pull up some wood fibers.
If you are gluing plastic (or ivoroid) to wood, be sure to use our FGW cement -or our new FCA contact cement. For wood to wood joints, use our FG glue. You might find that applying glue with our FGS glue syringe makes the job a bit easier. Some use cyanoacrylate glues (super glues), but the method for applying bindings in this way is not covered here.
Tear off several dozen pieces of binding tape (FT75) and have them ready at your workbench. Beginning at the neck, apply glue to the channel and press in the purfling (or purflings –sometime multiple lines are used). Then, follow by adding more glue and pressing in the binding strip. Apply the tape often–gluing and taping and as you go. Wipe away excess glue with a paper towel. There should only be only small gaps between pieces of tape. Apply the tape first to the outmost corner of the binding, and pressing the two strips tightly into place with your fingers, stretch the tape on to the top (or back) and then on to the sides. Check to see that the strips are seated properly and snuggly. Proceed towards the butt of the guitar until you are finished. Then, repeat the whole process along the other side of the instrument. When you are done taping, use several dozen strong rubber bands around the guitar to apply additional clamping pressure –especially at the waist. Allow the glue to dry at least 8 hours and then carefully remove the tape, pulling the tape off at an angle. A little heat from a hair dryer may help if you are having difficulty safely removing the tape.
In order to install shell purfling the procedure is roughly as follows. Here again you should do some test work before proceeding to the guitar:
Rout the channel and install the binding as above, but use a Teflon strip instead of purfling. You will be using a Teflon strip that is precisely the width of the shell you will be installing (TS63, TS79 or TS98 or TS104). When the glue has dried, remove the Teflon (it will not be held by the glue!). This should leave a perfect channel for the shell. Coat the slots with vinyl sealer to prevent the cyanoacrylate from penetrating the end grain of the spruce (and discoloring it). Then a light coat of cyanoacrylate accelerator is put in the slots and the strips are pressed in dry. Using a hard, smooth tool (such as a small spoon or a small veneer roller) start at the neck and slowly press the shell pieces into the channel. The shell will break into the channel. More breaks are better. Don't be concerned if the edges are not perfectly mitered as the break will look very natural, like veins in the shell. In curved areas around the waist, expect the shell to break in even more places. Now add the cyanoacrylate glue (FGHO) into the channel, being careful to avoid getting the glue onto the soundboard.
Leveling the Binding and Purfling
With plastic and/or wood binding you want the glued strips to protrude from the surfaces of the back and tops plates, and the sides, so that they can be scraped flush. Wait about 48 hours after the glue has dried and be sure to use a good, sharp scraper blade (LMI product code SCS gets you an entire set of scrapers, SCB-1 is the tool we recommend for sharpening the blades and it comes with excellent sharpening instructions). Making sure to avoid gauging the woods and keeping the scraper parallel to the surface you are working on, slowly remove material from the strips until they are flush. With shell inlay you will need to use sandpaper on a firm sanding block. Use sandpaper to soften the corner edge of the binding so that it is not too brittle.