STEP BY STEP - 5
BIND THE BODY
The binding on a guitar body serves several important functions. It
is decorative, it protects the edges from bumps, dings, etc and it helps
to seal the end grain of the top and back. It is critical that this
be done carefully or the appearance of the guitar will be severely compromised.
Before any of the steps are performed you must decide what binding and
decorative purfling will be used and then determine the exact dimensions
of the ledge that will accommodate them. There are many
choices in plastics and wood.
The binding on a guitar body serves several important functions. It is decorative, it protects the edges from bumps, dings, etc and it helps to seal the end grain of the top and back. It is critical that this be done carefully or the appearance of the guitar will be severely compromised. Before any of the steps are performed you must decide what binding and decorative purfling will be used and then determine the exact dimensions of the ledge that will accommodate them. There are many choices in plastics and wood.
Cut purfling ledge for back.
I always cut the purfling ledge (which is mostly on the back (or top) before I cut the binding ledge. In less mechanized days these ledges were cut by hand using a tool called a grammil. These are still available from some of the supply houses. there are also devices to use with a Dremmel tool. I prefer to use a router or laminate trimmer because the more powerful motor and the better quality bearings make for a more steady and rapid job. I use a router with ball bearing guided cutters (often called rabbet cutters). These can be purchased from several of the lutherie supply houses in a wide variety of "cuts".
I generally have mine custom made by a machine shop because I can get them sized exactly to my requirements. When sizing my ledges (rabbets) I generally make them about .010" wider than the binding/purfling combination that I intend to use. There are several reasons for this. First, I assume that the binding will swell slightly from the glue I am using. Second, if the ledge is slightly oversize, when I scrape the binding flush to the body the full edge will show - and one of the first and most obvious signs of a poor binding job is when the binding is of varying thickness at different points on the body.
The principal difficulty in cutting the ledges for the back is the curvature of the back which makes it difficult to keep the router (and the bit) perfectly parallel to the sides of the guitar. If this is not done the binding ledge will vary in thickness. There are several ways to correct for this problem. The simple method is to get a tilting base for the router and adjust it carefully to keep the bit parallel to the sides. Another method is to purchase (or make) one of the jigs which automatically hold the router in the correct position. There are several sources for such tools, including: I use the jig made by LMI. They also sell plans for making your own. Careful perusal of these catalogs may enable you to make your own tool at less expense.
Cut binding ledge for back.
Cutting the binding ledge is very similar to cutting the purfling ledge. A different cutter but the methodology is the same.
3. Cut binding ledge deeper to accommodate side purfling.
I use a line of purfling under my binding - i.e. between the bottom of the binding and the side. I like the look of this and have used it for many years. I like to miter this purfling into the purfling which outlines the end wedge and this presents a difficult problem (actually, several). First, the Binding ledge over the end wedge is not as deep as over the rest of the sides. So, the task is to cut the ledge over the end wedge at the exact depth I want for the binding and then to deepen the ledge everywhere else by an amount exactly equal to the width of the purfling. My method is as follows: I place a shim under the base plate of my router which is exactly the same thickness as the purfling (in my case, .079"). With this in place I cut the ledge over the end wedge. Then I remove the shim and cut the remaining binding ledge, which is thus deeper by the exact amount I need.
The second problem associated with
this form of decoration is making a perfect miter cut at the joint.
I will explain this later.
associated with this form of decoration is making a perfect miter cut at the joint. I will explain this later.
4. Cut top purfling ledge
Same as # 1 above, except the top is (mostly) flat and so it is not difficult to keep the bit paralell to the sides. I simply use a router with an oversize flat base.
5. Cut top binding ledge.
as #2 above.
Cut top binding ledge deeper to accommodate side purfling.
Same as #3 above.
7. File and sand top purfling ledge to ensure perfectly smooth edge.
This step is actually necessary for both the back and the top, but is more
important for the top because the softer wood of the top is more difficult
to cut smoothly.
I use a very small file with a fine edge and run it carefully around the
edge of the purfling ledge to smooth the edge. A straight file
cannot work for this in the inside curves at the waist so I make a small
curved sanding block of wood and stick some sandpaper (about 150 grit) to
it and use this homemade tool to sand the inside curve.
I use a very small file with a fine edge and run it carefully around the edge of the purfling ledge to smooth the edge. A straight file cannot work for this in the inside curves at the waist so I make a small curved sanding block of wood and stick some sandpaper (about 150 grit) to it and use this homemade tool to sand the inside curve.
Bottom line: Getting the binding ledges clean and consistent is a critical step in perfecting the cosmetics of your guitar. Work carefully!!!!
Prebend side purfling.
I put a piece of BWBW purfling under the binding on my guitars. I do it for purely cosmetic reasons as there is no structural benefit. If I were using plastic binding and purfling this would be easy since the plastic purfling bends easily in any direction. However, wood purfling does not easily bend in the directions needed for this purpose. It has a tendency to twist rather than bend easily. What to do? I bend the purfling on my side bending mold and to prevent the purfling from twisting I hold it tightly between two pieces of wood that are clamped to the bending mold. This is easier to show by photo than by description, so look here for the proverbial 1000 words. HERE Some builders glue the purfling to the binding before it is bent, and this seems to work. I have not done it this way so cannot report on its effectiveness.
Prepare miter joints for side purfling at butt wedge.
(Top or back are the same)
When I first started using purfling on the sides I simply ran it straight over the end wedge. However this looked bad to me so I soon started mitering the purfling on the side into the purfling which outlines the end wedge. The secret of doing miters such as this (which are not a clean 90 degrees) is to use a chisel which has its back face polished to a mirror finish (this is also good sharpening technique). When the chisel is placed on the purfling you can see the angle that the joint will make and cut accordingly. There is a photo of this here:
10. Glue miter joint of side purfling at end wedge.
Before I start gluing the binding in place I tack the miter joint at the
end wedge together with a drop of cyanoacrlate glue.
This makes it easier to
This makes it easier toensure that the joint is tight and stays that way.
Size binding as necessary.
The width of the binding should fairly closely match the height of the binding ledge. If it is too tall there will be a tendency for it to tip when taping it into place.
If wood binding, prebend binding.
I bend wood binding to the profile of the guitar before I glue it into place - this makes it much easier to install. I bend it exactly the same as I would the wood for the side.
13. Prepare back (or top) purfling for installation.
involves a brief soaking in water and carefully trimming the ends
for a good match.
14. Pre cut masking tape for application of binding.
I generally use a combination of masking tape and filament strapping
tape. The filament tape is best for sharp curves where some force is
needed to make a good joint.
Glue binding for top in place.
It doesn't matter much whether you do the top or back first. Start at one end (I start in the middle of the end wedge) and work around to the other end. Then repeat the process on the other side.
Glue binding for back in place.
Set aside for glue to dry.
File / trim top and back purfling/binding flush to top and sides.
This can be done in any number of ways. A router can be used with a bit that cuts just a hair above the surface, or it can be done with a scraper. I tend to use a wood rasp with the tip covered in tape so that it won't mar the top (or back) and do a follow up with a scraper.
Round over top and back binding.
I try to round over the edges of the guitar before I start finishing it. There are several reasons for this. First, from the builders point of view it is almost impossible to get a finish on a sharp edge without sanding or polishing through to the bare wood. A slightly rounded edge eliminates this problem. Second, a really sharp edge is uncomfortable for the player.
I do the rounding over with a combination of a small file and sandpaper. I use the sandpaper with a soft sanding block. I find that a combination of 100 grit and 150 grit will give a nice smooth edge that is smooth enough to finish.
Sand body for finishing.
This is a tedious but essential step. These days I use air sanders made by Dynabrade, a company which is widely considered the standard of the industry. They are lighter than equivalent electric sanders and yet are more powerful. And less noisy, although I still wear a set of ear protectors. I also use a down draft sanding table which considerably reduces the dust. (I still wear a dust mask).
I start sanding with 120 grit paper and carefully eliminate any working marks - from files, scrapers, etc. After this I wet the entire body to raise the grain. When this is completely dry (generally a matter of an hour or so, although I often wait til the next day) I sand again with either 150 or 180 grit paper and wet the body again. I they complete the sanding of the raw wood body with 220 grit paper. This is a good point to do a very careful quality control inspection of the guitar. Any glitches, nicks, scratches or the like must be fixed at this point.
Drill end pin hole.
I drill a hole slightly under 1/4" at this point so that I can put in a hook to hold the body while I am spraying it. It is relatively easy to find the center point of the end wedge. The hard part is ensuring that the hole goes in perfectly straight. I use a small portable drill press arrangement to do this. After the hole is drilled I camfer the edge of the hole slightly to ensure that the wood does not break out when I put in the hook.
Install hook for finishing.
This is pretty straightforward.
Install soundhole cup for finishing.
Before finishing the soundhole must be blocked off to prevent finish from getting inside the guitar. I use a old (but clean) margarine dish or a chip dip dish and a piece of foam rubber on the inside to keep it tight against the inside of the top. the main consideration is that the dish must be slightly larger than the soundhole so that the edges of the soundhole are fully finished.
Install dovetail handle for finishing.
I have a selection of handles which have the male dovetail joint cut on one end. This is put into the female dovetail cavity on the body. A light tap with a hammer ensures that it will stay put. Then I can hang the body from the hook in the spray booth and use the handle to maneuver the body as I spray it.
Spray entire guitar with vinyl sealer.
I use McFadden's lacquer products, as do most guitar makers I know of. Either vinyl sealer or traditional sanding sealer will work as a first coat. However the vinyl sealer gives a slightly more flexible finish and helps to prevent cold weather checking, a real advantage here in Minnesota. These days some builders are switching to finishes other than nitro lacquer. Some are using a cured polyester (either UV cure or some other catalyst) and some are using waterborne finishes. I think these are good ideas but so far none of them look as good to me as traditional nitro lacquer. So, for the time being I remain a stick-in-the-mud on this issue.
Apply wood pore filler on back and sides, set to dry.
I use McFadden's paste pore filler. It is simple to use. I wipe it on with a cloth, then mash it in with a rubber squeegee. Once it is partly dry (when the surface develops a dry looking haze - a matter of perhaps 5 minutes) I wipe it off, across the grain. Burlap is the traditional material to use for this. I then let it dry for about 24 hours (or more)
Sand filler till surface is clean.
When the filler is completely dry I resand the body with 220 grit paper. This ensures that there is no filler or color from the filler on the surface of the body - only in the pores of the grain. I prefer this look. I almost never use stains or other coloring unless I am doing something like a sunburst. On rare occasion I have, at a customer's request, stained a mahogany body dark (like a Martin D-18) but that is not my personal preference.
Apply coat of vinyl sealer.
Because the sanding in the last step has removed some of the vinyl sealer I recoat the guitar with vinyl sealer at this point.
Apply 4 coats of Nitr o lacquer.
The vinyl sealer needs to dry for a few hours and then is lightly scuff sanded. At this point I apply 4 - 6 coats of lacquer. I find that the individual coats should dry about 45 - 60 minutes so it is easy to do this many coats in one day. I generally add an extra coat or so on the edges since this is the easiest area to sand through.
Wait at least two days (preferably 1 week)
I generally leave the guitar body to dry for at least a week. This is not a big problem as I am generally working on 8-12 guitars at a time and my spray booth will really only handle about 4 bodies. The longer you wait the more the lacquer will have dried out (off gassed its solvents) and in the end this will result in a smoother finish.
Drop fill all pits, blemishes,
While the guitar is drying I will inspect it carefully for any voids, pits or deep grain and drop fill them with lacquer. In some cases where there is a deep void and the lacquer has a tendency to wick into the crack I find that cyanoacrlate works well for this step. The goal is to ensure that the final finish will be perfectly smooth with no blemishes. The sooner the better is the word on this step.
Sand lightly with 220 frecut paper.
At this point I do not attempt to get a perfectly flat finish. I want to remove most of the grain that might telegraph through the finish and to flatten out small voids and fills. When this sanding is done it is easy to see where additional filling will be necessary, and I do this now. Take as long as necessary to do it completely. Overfilling is not a problem as we will sand the lacquer at least two more times.
Spray 3 additional coats of nitro lacquer
Just as before, extra coats on the edges and about 45 - 60 minutes between coats.
Drop fill all pits etc.
Once again, check to ensure that voids, pits and telegraphing grain is filled.
Wait 1 week.
This is the easy part.
Sand to flat surface with frecut paper.
These days I do this in two steps. A light sanding with 220 grit in my Dynabrade sander. The normal sander has a 3/16 orbit and cuts agressively, making it easy to get a nice flat finish. Then I switch to a Dynabrade with a 3/32 orbit, and 280 grit paper. This leaves a much smoother finish which is easy to coat with two coats and get a very nice final surface.
Spray 2 coats of nitro lacquer - thin final coat.
Much the same as before except that here great care is especially important since very little sanding is left and flaws will be hard to remove.
Wait at least 1 week.
Another easy part.
Sand to flat with 600 wet or dry.
For many years I did this entirely by hand. 600 wet or dry paper, a hard rubber sanding block and water as a lubricant. I put a little liquid soap (I like Murphy's Oil Soap) in the water to enhance the lubricating qualities and ensure that the paper doesn't unduly load up. These days I use a small 1/4 sheet air powered sander that speeds this process greatly. In either case the goal is a perfectly flat finish, no voids, no grain showing and very fine sanding marks. This is now ready to polish.
Wait at least 24 hours - preferably more.
The sanding will have softened the lacquer just a bit so wait till you begin polishing
Sand with 1000 or 1200 wet or dry.
This step is optional. I like it but made many guitars without doing it.
Wait at least 24 hours.
Every time you sand or polish the surface softens a bit so wait for it to harden before the next step.
I use a power buffer - large cotton wheels on a buffing machine and dry polishing compounds. This is incredibly time and labor saving, plus it is essential for my health. In olden days when I did a lot of polishing by hand my shoulders hurt and ended up getting cortisone shots twice - something I do not intend to repeat.
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2219 East Franklin Ave.
Minneapolis, MN. 55404