Wednesday, March 28, 2012

Guild D-40 (Continued)

Wow. Lots of exciting stuff going on with the Guild.  Yesterday, after being clamped-up for more than a week to correct the guitars belly problem (see the previous post) I removed all the clamps and cauls. Well, the news is good but not great.  About half of the belly rise is gone, which means that the neck angle will not need to be reset.  I will, however, have to make a new, slightly taller, bridge to get the proper neck-set.

But I still have to put a shim under the tongue, and to do this the neck has to come off.  This requires a couple of very high-tech pieces of equipment, lots of rags, and a bit of elbow grease.  

The is the first piece of high tech equipment..haha...a $25 Mr. Coffee cappuccino maker with a milk steamer.

I pulled the 15th fret and drilled a small hole through the fretboard to get access to the dove tail joint pocket. No worries, the fret crown will hid the hole.  Then I connect the steamer to a very large gauge needle so I can direct steam into the dove tail pocket.  The idea here is that the heat and moisture of the steam will loosen the dovetail joint so the body mortise and neck tenon can be separated.   Remember that I had already separated the tongue from the top so the only thing left to detach is the dove tail joint that holds the neck to the body.

This brings me to the second piece of high tech equipment....a jig designed to help push the neckdove tail tenon out the the mortise in the guitar body without stressing the joint.  I have a homemade one of these but the pictured jig is from Stew Mac.  The next four pictures show the jig, the steaming process, and a photo bomb (my daughter is home for Spring break from college and her friend jumped in the shot....kids!)











This was a VERY VERY difficult neck to remove.  Not only was the mortise glued to the tenon, which is all that should be necessary, but the neck heal was glued to the body creating a glued surface that the stream could not reach.  Also, the heal had a crack where the strap button was installed.  Steam made its way into that crack and wreaked havoc with a bit of the brittle lacquer finish on the heal.  But, I finally got it off....whew!

Pic showing the body's dove tail mortise

Not a very good pic of the neck tenon

Upon closer inspection I could see why the heal had been glued to the body.  This dovetail joint is not properly shaped to do what it is supposed to do....that is, pull the neck into the body as the tenon is inserted into the mortise.  So, if the heal had not been glued securely to the body, the neck would tilt forward with the slightest bit of force created by string tension.  Maybe it came out of the manufacturer this way or maybe it was modified during an earlier repair....but in any event, without rebuilding this dovetail joint so that it functions properly, the neck heal will have to be glued to the body again.  And I really don't want the next repairer who needs to remove this neck to have to deal with that nightmare.

Stay Tuned

Wednesday, March 21, 2012

Under the Bench Lamp: Guild D-40 (Continued)

I have a few spare minutes to get all of you eager readers caught up on the Guild D-40 repairs. Since I last blogged the guitar spent several days in a properly humidified environment, which BTW did not improve the belly behind the bridge or the depression in front of it but I'm still glad I did it.  Now I know that before I start making any change to this sweet sounding guitar, the woods are somewhat acclimated to 45ish % relative humidity at 70 degrees, which is how it should be stored.

The first step of the belly-reducing exercise I used in this case requires that I remove the bridge.  This was not so easy.  It took more than a hour and plenty of hand strength to very gentle coax the bridge loose. I heated it to around 150 degrees with an iron that I bring to temperature on a hot plate.  Then I used a fillet knife and several types of spatulas to separate the bridge from the top.


Next step is to remove the pick guard. I am going to clamp the top to an inflexible surface and the pick guard is just too thick to leave there...it will prevent the top being push flat.   In case I might damage the pick guard while removing it I carefully copy it before I do anything....this way I can shape a replacement more easily if necessary.  Once copied on to sign makers tape I used a lamp to very slowly and gently warm it up.  Once warm I used a thin blade spatula and up it came.  No damage so I can reuse it if I want.



A 100 watt spotlight generates plenty of heat for this job.  If you look closely you can see the sign tape. 

A shot of the nice and clean bridge and pick guard removal.
Now for the main event of trying to remove as much bridge-rotation belly as possible.  First, I warmed the bellied area of the top with the lamp.  Then I used a wet sponge to moisten the bridge area and the inside where the braces meet the top.  And now for the clamping.
In the area of the belly and depression, the top is being forced flat against a relative inflexible thick piece of tempered glass.    
I will let the D-40 sit for the better part of a week before un-clamping.  Then, depending on the result of the belly-reducing effort, we'll decide on the best next steps.

Stay Tuned

Thursday, March 15, 2012

Under the Bench Lamp:  Guild D-40

Okay, this is the second guitar repair that I have featured on my relatively new web-site blog.  I believe that this guitar repair will prove to be blog-worthy...it has a couple of issues common to older guitars (this Guild has been been strung up and played for decades),  it's has a very sweet sound so it will be a rewarding feeling to bring it back to its full playing potential.  And finally, I'm going to retrofit the Buff Feiten Tuning System, a proprietary tuning system that I am authorized to install.
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This is the Guild D-40, made in Hobokin, NJ. 
The biggest issue with this guitar is the fact that, after years of being subject to string tension, the bridge has "roatated" and is now leaning toward the sound hole.

This is a pic of a handy specialty measuring devise that allows me to quickly and accurately measure the amount of deflection in a guitar top. Just out of frame,  you can't see the supports placed directly over the top/side joint.  In the center of the pic, in-between the D and the G strings, you can see the dial actuator resting on the top immediately in front of the bridge.

Under string tension, and as a result of the rotating bridge, the top has a .075 inch depression in front of the bridge.  And, behind the bridge, the top has a .125 inch bulge.  Sadly, but predicable, this flat top acoustic no longer has a flat top.

The rotated bridge has had a cascading affect on this guitar. As the bridge has leaned more and more forward, the bridge saddle has lowered relative to the playing surface.  This lowering of the bridge saddle over time has changed the position of the strings relative to the fret board...the string are getting closer and closer to it.  The result is a neck angle that is over-set.  And, because of the over set neck angle, there is some mild buzzing on the lower fret.  Also, there is very little meat left on the lower frets.  I suspect that's because a guitar repairer, in an effort to set-up the guitar so it can be played with a sinking bridge, has lowered the frets to stop any buzzing and to help compensate for the over-set neck angle.

There's another issue with the guitar, and I suspect this is a result of some not-so-careful repair work. This guitar left the factory with a 12" radiused fret board.  But, now it has a compound raduis.  The fretborad has a 15" radius near the nut that graduates to a 12" radius at the 20th fret.
Under-string radius gauges.....another very handy specialty tools for fast and accurate guitar  evaluation.  This bridge saddle checks out at a 12"radius.  But, as I mentioned above, the fret board radius is 15" further down the neck.
Changing a cylindrical fret board into a conical one can happen when a repairer attemps to level the fret board without being careful to preserve the radius. As I learned in the Galloup School of Lutherie,  in all fretted instrument repairs, one must "always respect the radius".

Also, the nut and saddle are plastic.....and that simply will not do!

So, here's a ruff outline of my plans for this guitar:

  • Humidify
    • Its been dry, I am going to put the guitar in a properly humidified environment for several day before I proceed.
    • Once it's acclimated, I'll sting it up with a set of the stings and remeasure and record all the realvant features that I plan to address.  This way I can quantify how the guitar has been improved.
  • Structural checkup
    • Give it a thorough going over to find any structural issues that might be contributing to the rotaing bridge problem.
    • Fix any loose braces
  • Bridge removal
  • Top flattening
    • I'll try a couple of different techniques
    • There will be some more interesting implements involved here....very blog worthy IMHO
  • Bridge replacement
  • Deluxe setup
    • Adjust neck
    • Level and reestablish the fret board radius.......yes, I know this sounds like an oxymoron but when I say level, I mean from end-to end, not side-to-side.
    • Refret
    • Install Buzz Feiten Tuning System...this includes a shelf bone nut and saddle and usually involves re-routing the saddle slot.  According to my initial determination of where the saddle should be on this guitar, as compared with where it is actually located,  moving the slot is disparately needed for proper intonation.
My plan is, of course, subject to change based on how things go.  So long as time permits, I hope to be able to blog about each of the above steps.

Stay tuned!

Friday, March 9, 2012

Under the Bench Lamp - Norman B20 - Done!

Well, I completed the repairs on the Norman B20 and want to share a little information about what I did and the final results.

Now that the shim is in and looking good, it's time to prep the guitar for a precision refret and setup.  First step is to string it up to pitch using the same type and guage of strings that the owner wants on the finished repair.  Then, I put it in the neck jig....

Once in the jig, the first step is to adjust the truss rod to get the neck as flat as possible.  

Once I have adjusted the truss rod so that the neck is as flat as possible, I make a final check to assure that the guitar is securely in the jig and then I "zero-out" the deflection dials that measure neck movement. This will allow me to put the neck back into it's under-tension playing position before I level the fret board.

Now that the deflection dials are zeroed, its time to heat and remove all the frets. The key here is to be very careful and take your time....I don't want any chip-out.

With the string off and the frets removed, the deflection dials are no long zeroed....the neck has moved from its under-tension playing position.  So, before I level the fret board, I used the neck jig's to "push" the neck back to it's playing position.  If I did not take this step, neck leveling would not give me a good result....the neck needs to be positioned as if it was under string tension BEFORE I level the fret board.  If your guitar repair person does not use a neck jig for refrets, you may want to find a new one.

Now, the guitar is in the jig, the neck is back into its original strung-to-pitch position, and the frets, string, nut, and saddle are out of the way.  It's time to get out the grease pencil and the leveling bar.  I mark the surface of the fret board with the grease pencil so I don't remove any more material than necessary to achieve a level playing surface.  Also, I use very careful sanding strokes to make sure that I don't change the fret-board radius.

Not a great picture but I am trying to show the guitar in the neck jig and the leveling bar.  The bar has 320 grit stick-on sand paper attached to it.  Also, you can see the tension strap and securing posts that hold the neck in the zeroed position.
 It does not take many passses to level the fretboard.  So, now it's time to take it out of the jig and install the new frets.


Here is a shot of some of the tools I use for refretting.  The diet root beer is a must-have in my shop
I don't have any pics of the fret installation process but, in short, it goes like this.  Wax the fret board for easy cleanup later, slightly over-radius the fret wire in the fret bender, cut all frets to length, apply a couple drops of super glue on the fret tang, put fret in position and hammer into the fret slot.

Now it's time to dress the frets.  Since the fret board is flat from nut to the last fret slot, leveling the fret tops should go smoothly.

Before I start leveling, I string up the guitar once more, tune it to pitch and pop it in the neck jig and make sure the neck is flat and secure....can you tell I love my jig....it really does take all the guess work out of a job like this.

Now, before we go any further, let's protect that fret and sound board, with masking tape and guards, from the leveling bar.
Ready to level the frets.  I use the same technique that I used when I leveled the fret board.....Respect the radius
Okay, the fret are level.  Next I crown and polish them.  Sorry, no pics....I will show how I do this in another post.

Time for a new bone nut and compensated bone saddle.  Remember that the factory had used plastic....and that just simply won't do.

I have some really cool tools that make it possible to shape a very presise nut and compensated saddle. Here is one of them.  I will highlite more in future blogs.
This is a string height guage.  It allows me to set very precise string heights at the first fret...or any other fret for that matter.  In this case I am going very low....about .020 on the base side down to .014 on the treble side.
Time to restring with a fresh set and check this thing out.
Done!
I am very happy with this repair.  It plays great now, really great....and when I got it, it was nearly unplayable, especially if your thing is fingerstyle.  Low action (5/64 bass side, 3/64 treble side at the 12th), no buzzing, almost invisible under-tongue shim to allow for a flat neck the entire length of the fret board, custom bone nut, compensated bone saddle, shiny new frets, and a bright-sounding new set of string.