STEP BY STEP - 7

ASSEMBLE THE GUITAR - INSTALL NECK

  1.                    Check fit of neck to body.  Verify centering, back angle and fit of heel to body.   

     This is one of the most critical steps in the entire process of assembling the guitar.  The entire geometry of the guitar depends on it.  This is a task best learned through experience, but several pointers can be mentioned.  Most of the adjustment is done to the edges of the heel of the neck where it meets the body. (I call these the "cheeks" of the heel.) If you remove wood from one side the neck will move to one side or the other relative to the center line of the guitar. If one removes more material from the heel near the heel cap the neck will angle back from the plane of the top and conversely if one removes more material near the fingerboard the neck will angle forward relative to the plane of the top. 

2.                    Adjust any of the above as necessary.  

     I try very hard to have all of the neck fitting done (or very very close) before I finish the neck and even before I attach the fingerboard.  This makes access to the cheeks of the heel much easier.    I strive to have the centering of the neck accurate to within 1/64th of an inch - and in no case more than 1/32" off center.  I try to have the neck angle back so that a straightedge laid on the fingerboard will be 12/32" above the top at the point of the saddle.  this allows me to make a bridge that is 12/32" high and still have a reasonable protrusion of the saddle above the bridge.  

       One technique that should be learned is what I call slip fitting a neck.  Once the basic angles are correct the cheeks of the heel must fit the body perfectly - any failure here is very visible and will make the guitar hard to sell.  The technique is this:  Hold the neck in place with a strip of sandpaper (I use 150 grit) between the neck and the body, with the grit touching the cheeks of the heel.  Applying some pressure to the neck, carefully pull the sandpaper out from between the cheeks and the body (one side at a time_  This will essentially scribe the heel to the body and result in a factory perfect fit.  If the body is finished I put a strip of thin low tack masking tape between the body and the heel to avoid scratching the finish.  

    Once the neck is properly located one must make sure that the dovetail is tight - the joint should be tight enough to hold string tension without glue.  It is rather difficult to describe this - but if there is any motion in the neck/heel, the location of that motion (and the amount of motion) should tell you where to add shims or remove wood.  The object is a tight fit when the neck is clamped fully into the box.  I generally use mahogany veneer to make any shims - it is a compatible wood (i.e. it is the same wood) and it is easy to work.  One advantage of using shims is that if you remove too much wood from a shim it is easy to start over.  

3.                    Verify location of fingerboard on top, mask and remove lacquer.  

     I find that it is easiest to get a good finish on the body if I do not mask off the area where the fingerboard will be glued on.  So, once the neck is fully fitted I carefully mask off the space and remove the lacquer.  I generally let the lacquer run under the fingerboard perhaps 1/16" so as to ensure a good looking joint.  I use paint stripper to remove the lacquer.

4.                    Recheck fit of neck - several times.  

      The fit of the neck is critical - both structurally and cosmetically - nothing flags poor workmanship so easily as a poorly fitting neck.  Here is a good place for the old adage of  "measure twice, cut once" - although here it would be "Glue once."

5.                    Prepare clamps and cauls.  

    Not much to say here - I use a large C clamp to hold the neck in and two small C clamps to hold down the fingerboard extension.  A caul on the fingerboard will take care of that side and one on the back of the body to protect the finish.  and one inside the top to prevent crushing the braces there.

6.                    Glue in Neck and fingerboard extension.  

   I use Titebond here.  I need more time than hide glue allows, Titebond works well and can be undone with steam if that ever becomes necessary.

7.                    Clean up all glue squeeze out.  

   I use wet (and then dry) paper towels for this.  A small 6" ruler helps to get the towel (rag) into the tight corners. 

8.                    Let glue dry for 24 hours.  

   This is easy enough.

9.                    Verify correct location of neck.  

   Hopefully all is well. 

  BRIDGE

  1.                    Select ebony for bridge blank.  

    Other than size,  the critical issue here is no cracks or checking.  Look carefully.  Woods other than ebony are perfectly acceptable - I use Brazilian Rosewood from time to time. 

2.                    Surface bottom to smooth.  

   I use a flat top so the bridge can be flat.  If you decide to use a domed top the bridge will have to be shaped to fit.  This is generally done after the bridge is shaped but the progression is not critical.

3.                    Rough cut profile.  

     I trim roughly with a bandsaw.  I save the scraps - ebony dust is sometimes necessary for various tasks and the scraps can be used to make it. 

4.                    Trim blank to profile on shaper.  

    I use a shaper because I have one and it is fast.  You can easily do this by other means, including hand tools.  symmetry is important (if your bridge is intended to be symmetrical - mine is).  The easy way to achieve this on a shaper is to have a one sided jig.  I cut one side - flip it over and cut the other side.  Voila  - a symmetrical bridge profile.  A router table will work equally well. 

5.                    Band saw rough cut for ears of bridge.  

I use the band saw to roughly scoop out the ears (wings) of the bridge.

6.                    Thickness ears on drum sander.  

    I have a small drum sander (built into my lathe) which does this quickly and easily.  Most any method will do.

7.                    Sand top profile on bridge blank.  

    The top of my bridge is not flat - it is curved to (more or less) match the arch of the fingerboard.  It also tapers from front (about 12/32") to back (about 1/8").   I do this first on a belt sander to rough shape and then by hand - first with a rasp and then with  hard or relatively hard sanding blocks to avoid rounding over the edges which are intended to be sharp (mainly the point where the curve of the ears meets the surface of the top of the bridge.

8.                    Finish sand bridge.  

   I generally sand ebony to a 400 or 600 grit finish.

9.                    Locate bridge on top - check it several times. 

     Check for distance, centering and perpendicular to centerline of guitar.    Again, measure twice, cut once.  Be very careful at this stage.  I speak from experience - I have several times placed a bridge for a 14 fret guitar in the location for a 12 fret guitar - requiring a whole new top. 

10.                 Scribe finish around bridge.  

    I use an exacto knife with a # 11 blade.  I use a fresh one every time and I heat the blade in a propane torch before cutting the finish - it helps to avoid any chipping.  Here is another area where precision is important and lack of it will be glaringly obvious.

11.                 Remove finish from top under bridge.  

      I use paint remover - followed by very careful use of a chisel to remove all the finish up to the scribe line.  I then sand the bare wood of the top carefully to ensure a clean surface for gluing.  Some people use a chisel and scrape the finish away.  Others use a mask placed on the top before finishing, which is then removed prior to gluing.  All of these methods work well- I am just used to doing it one way and see no need to change.

12.                 Locate bridge pin holes.  

     Placing the bridge on the top in its "divot" in the finish, I hold it securely in place with masking tape and lay out the placement of the bridge pin holes.  I place the pins on a semi circular arch so that all 6 holes are not on the same grain line, which I think may help to reduce bridge splitting.  Martin has used 6 in a line for a long time with no great problem so probably either method will do.  Others use a straight line that parallels the slanted saddle, which avoids the splitting issue and keeps the string angle off the back of the saddle uniform for every string.  This does make intuitive sense, although I doubt that it is a critical issue either way.

    A word about string spacing.  Most makers will space the bridge pin holes evenly.  I do.  An argument can be made for a proportional spacing which allows for the different thickness of the strings (i.e. space so that the gap between strings is equal, instead of having the centerline of each string being equally spaced.)  As I say, I use equal spacing based on the centerlines - use your own judgment.

13.                 Drill bridge pin holes.  

   I then take the bridge off the top and drill the holes (with a 3/16" brad point drill).  I drill them at a slightly back leaning angle - mostly a cosmetic thing, I believe.  I then place the bridge back on the top and drill two of the holes through to top, and ream them with a tapered reamer.  I then use tapered poly plastic locating pins to ensure that the bridge will not move when I apply gluing pressure.

14.                 Glue on bridge.  

   These days I glue on bridges in a two step process.  I use hot hide glue.  Because this has such a short open working time I begin with a vacuum clamping jig - for about 2 minutes.  Then I switch to metal C - clamps.  The trick with these clamps is to make a caul for the inside which spans the braces and gives a good surface for the clamp.  Also a caul for the top of the bridge. 

15.                 Locate and cut slot for saddle.  

     Here again, measure twice, cut once.  I measure twice the distance from the nut to the middle of the 12th fret and add 1/16" on the treble side and 3/16" on the base.  This gives a good location for proper intonation.  I use a  1/8" wide saddle and can easily shape the top of the saddle for good intonation.  

   I cut the saddle slot with a laminate trimmer (a small router).  These are powerful enough to do the job cleanly and with some speed.  I have a jig which I made which holds the router evenly above the top and which and be carefully placed so that the slot is in the right place.  As you can see from the photo, it is a relatively simple jig.  

16.                 Drill out and ream bridge pin holes.  

   I use a tapered reamer designed for bridge pins - it works quickly and easily and ensures a good fit.  The pin (with the string in place) should fit snugly but not tight - you do not want to create a wedging action which may split the bridge. 

17.                 Cut slots in bridge for strings.

    I use a saber saw blade to rough cut these slots and final shape them with a needle file.  They should be properly located - i.e. evenly spaced and facing directly forward.  

hoffmanguitars@qwestoffice.net or choffman@hoffmanguitars.com