Hoffman Guitars - Custom built handmade guitars

STEP BY STEP GUITAR BUILDING

This section is an attempt to break down my building process into a number of discrete steps. As time goes by I will add descriptive paragraphs for each step, and links to relevant photos. Until I get those links done, you can follow along with these descriptions by going to the relevant pages in this site's section on building guitars.

Top

There are two main considerations here. The species of wood - Spruce ( Sitka, Adirondack or Engelmann) Cedar, Redwood, Mahogany?? There are some descriptions of these woods here. Then you have to examine the wood and see if the quality is acceptable. Some thoughts about this are found here.

Generally this is not a problem - the wood I buy is generally free of defects. However, I still look at the grain to see if their is an orientation which makes sense to me, and if there are defects which can be kept outside the profile of the top. One place to "hide" small defects is in the sound hole cutout. Wood that comes from relatively small trees (i.e. Adirondack spruce) may have more small defects that must be avoided.

There are any number of ways to do this. My preferred way is to use a jointer - I have a very good 6" Powermatic jointer and if the blades are new and well adjusted, it works very well. I have a light box to look at the joint and if it is not perfect I try again until I get it right. If the jointer is well set up a perfect joint takes only one or two passes.

There are a couple of issues here. First, what glue to use. Lately I have been using hot hide glue - at least for glue joint on the top. There is some reason to feel that this will improve the sound of the guitar since it dries to a harder less flexible final state. Also, it is clear that there is less "creep" with hide glue. Titebond is easier to use, and certainly is a fine choice - I used it for years and still use it for many parts of my guitars.

The other issue is how to clamp the pieces of the top together. Look here to see two jigs which I use. There are others, but these work well and are quick. The important elements are to apply even pressure to the glue joint and pressure across the joint to keep the two pieces in register.

5. Lay out and drill registration holes, including 3/8 hole for sound hole cutter.

This is something I do to allow the use of certain jigs later in the process of building the top. Look here for a photo of a simple jig to do this. I also drill a small (3/16") hole located so that it will fall in the neck block. This hole is exactly on the centerline, as is the corresponding hole in the neck block. this helps to ensure that the top will be centered on the body.

One of the reasons I build in batches is that my shop is not large enough (nor do I have enough tools) to set up a "station" for each job. So, if I am setting up a tool for a specific job, it makes sense to do a lot of pieces rather than waste the set up time. In this case I use a special table under the drill press that has a bushing for the center post of the cutter. This is essential to ensure a steady cutter. You can also see that I have a special piece to hold down the top while I am cutting the rosette. This is nothing fancy - just a heavy piece of MDF with foam on the bottom. It really doesn't need to be clamped, although I generally do.

This is another job that can be done in a variety of ways. I used a router for many of my guitars, and then decided that a fly cutter would work better (i.e. make a cleaner cut). Router bits have a tendency to tear out the grain of the wood in certain spots around the circumference of the hole. If the fly cutter is sharp, and is held steady, it will cut cleanly. I find that the speed of the cutter is not terribly important but it is important to feed it smoothly and slowly into the wood.

There are several ways to do this. For years I used Titebond glue and this worked well. Recently I have been using hide glue since the braces on my tops are glued on with hide glue. Even more recently I have been using cyanoacrilate glue. This works well, is fast and due to the penetration of this glue there seems to be fewer voids etc in the rosette. If you use cyanoacrilate it is essential that you first seal the slot with sealer (I use vinyl sealer). If you do not the glue will penetrate the end grain where it is exposed in the slot and discolor the top.

It is quite important that the purfling or other decoration fit well into the slots you cut (if that is how you do it). If they are too tight the fibers of the top may crush and the top will look bad. Too loose and the rosette will have gaps and look sloppy.

The best tool for this job is a wide belt sander. Unfortunately this is a very expensive ($6000.00 ++) tool designed for industrial use. I rent time on one owned by a local cabinet shop (I sometimes use Jim Olson's). I buy my own belts (partly to keep from damaging theirs and partly to avoid using theirs) and pay an hourly fee. I strongly recommend this method - the tool is unquestionably the best for the job. I use a 120 grit belt for the last run through the machine and this leaves a very smooth surface. A good sander can hold tolerances of about + or - .003 which is quite sufficient. More recently I have purchased a large Drum sander (made by General). The main reason for this is that the wide belt sander currently available to me is only moderately accurate and the Drum sander is very accurate ( + or - about .002 -.004). So, I do rough heavy stock removal on the wide belt sander and final thickness in the shop on the drum sander. Another advantage is that it is easier to do small runs or pieces (such as brace stock, headstock veneers, etc.)

For no particular reason I cut the soundhole out after the top is sanded. As with the rosette slots, I use a fly cutter. Fly cutters have a tendency to tear out wood when exiting the wood (but not when entering) so the critical thing to remember is to cut from both sides so as to avoid tear out along the edge of the hole.

The jig is simply a board with a hole exactly the same size as the sound hole. If I clamp the top to this I can use a piloted round over bit to round off the edge of the hole. (Thanks to Jim Olson for this (and many other) jig ideas.) Some hand sanding is still required but even so this step makes for a nicely finished look to the soundhole. PHOTO

I cut the bracing stock on my table saw - nothing very technical about this. The really critical issue is to ensure that the blocks of spruce you are using are quartersawn and without runout. This is a matter of buying from a reputable and knowledgeable supplier. The sizes I use are:

After the stock is cut I run it through my drum sander to get the wood to the exact thickness.

I consider this to be a very important task. There are two issues: First, the joint must be a very tight fit. Second, the angle of the X is an important element in creating the "signature sound" of the instrument. The joint can be cut quite simply with a fine saw and a few files to refine the fit of the joint. However this proved tedious and not as accurate as I wished. So, quite some time ago I made a small and simple jig that enables me to cut this very accurately. (PHOTO) It uses a router to cut the slot. I use a 5/16 width bit (since that is the width of my braces). If the wood is exactly that thickness (which I did in the last step on my drum sander) a very tight fit is achieved. One can also cut the joint in slightly oversize wood and carefully sand the pieces until a tight fit is achieved. I cut the slot so that an equal amount of wood is above and below the meet point of the joint. Some think that one or the other should be larger - presumably to add stiffness to the joint. Some makers will add a small piece of wood to bridge the "open" notch on one brace, and Martin covers this joint with a small piece of muslin glued in place.

This may seem obvious, but it is not. Many guitar makers build their tops with a slight dome (about a 25' - 30' radius) and for them the braces must be made with that curvature built in. I do not do this. Why?? Those who do this (which includes many vintage guitars) believe that it adds to the strength of the top, thereby making it possible to make a slightly lighter top. At any rate the feeling is that it improves the sound of the guitar (and, coincidentally makes getting the neck/body angle a bit easier to achieve (more on this later). I am not convinced. I have tried domed tops and felt that either they did not sound better or that the sound became more fundamental with not enough overtones. Of course there is no "right answer" on this - tone is so highly subjective that it would be impossible to come up with a single right answer. Suffice it to say, I continue on my merry old "hide bound" ways.

I should note that one of my characteristics is that I am lazy - so as long as I can mechanize a task without negative effect, I will do so. Using a jig and a special cutter on the spindle shaper I rough out the tops of the braces. For the X brace and the tone bars, this involves rounding the tops and introducing the scalloping I use. For the braces under the fingerboard, this is just rounding the tops. This saves some work and introduces just about the right amount of uniformity to the end result. This still leaves wood for me to carve away as I do the final shaping and adjustment of the bracing which will (hopefully) yield the specific sound I want.

16. Mark placement of braces on top and/or locate top on registration pins in gluing fixture.

I have a template for each of the tops I make. These are made of 1/8" Plexiglas, and the location of the braces (and soundhole and shape of the guitar) are deeply etched. This way I can locate the top on the wood with a full view for proper placement and I can mark the location of the braces. For the points where two braces intersect inside the edge of the template I drill a small hole in the template to make it easy to mark that spot. PHOTO

This is a critical step. As noted above, I am currently using hot hide glue for gluing up tops, including the braces. This is more labor intensive but I am coming to believe that because hide glued dries "harder" and less flexible it may improve the ability of vibration to transfer to all of the top. This might improve the sound. (I can think of no scientific way to prove this) Additionally, hide glue is less likely to creep than Titebond or similar glues, which would be a benefit in the heat or even just over the (hopefully) long life of the guitar. I generally glue the X joint together, then glue the X brace to the top. (PHOTO) Next is the bridge plate. (I currently use a maple bridge plate about .100 thick and 1 3/4" wide.) Next I glue in the "fingerboard braces" and the tone bars. Finally the finger braces. By doing this in stages I leave plenty of room for cleaning up the glue squeeze out, another essential task. I use a whole variety of clamps to ensure good solid clamping pressure over each brace. Some makers use (and swear by) a "Go bar deck" but I have never used one (I was too set in my ways when I found out about this alternative.) I am also experimenting with vacuum clamping braces. I think this will be the best solution to getting very uniform pressure, but so far I am not happy with the vacuum jigs I have made. I may simply have to go buy one.

As each set of braces is clamped to the top, I final shape them. This involves carving them to a final shape - my preferred shape is a fairly thin tall brace tapered from a width of about 5/16 to almost a knife edge on top (actually, perhaps a 1/16 radius). I use a variety of straight and angled chisels to do the carving. After I am satisfied with the carved shape I sand the braces smooth (down to a 220 grit sandpaper). I do this entirely by hand, but note above that I do a fair amount of preshaping of the brace on my spindle shaper. This does save some time and labor in the final sanding.

I use maple for my bridge plate and I sand it to about .100". I like the sound I get and the wood is easy to come by.

I make and install this "brace" on my tops after the X brace is in place and before the other braces are glued on. This makes it easier to fit it closely to the legs of the X, and yet still have room for cleaning up glue squeeze out. . Some makers do it first and glue the braces around it. I do not think it makes much difference either way. The main point is to ensure that the plate fits tightly between the legs of the X brace. My bridge plate is currently about 1 3/4" wide. Any narrower and I fear the top will rotate too much. Any wider and I think the tone is impeded. Another balancing act about which everyone will have different opinions.

These are the last braces put on the top. They are carefully fit to the leg of the X brace and the first of the fingerboard braces.

On my guitars the ends of the X brace and the fingerboard braces are notched into the linings. The others are cut short of the linings. This gives what I believe is the proper balance of strength and flexibility of the edge of the top. I generally do this when I am fitting the top to the ribs.

It is a point of pride for me (and most makers I know) that the inside of the guitar be as nicely finished as the outside. So, I carefully inspect the top at this stage to ensure that it is up to standard.