Straight Pull Headstock Conversion, "Finished" but Unfinished

I still have to adjust the nut slots and tweak the bridge and saddle, but this guitar is now playable in its new 3+3 straight pull configuration.  We'll see about stability and durability.  Here's a detail of the headstock with its battle scars.  The new bone nut is in place, and the Sperzel tuners.

Here's the whole guitar:

Acoustic Guitar Straight Pull Conversion

Straight pull means that the strings, when viewed from directly above, come over the guitar nut and drop to the tuner shafts without an divergence to the left or right.  Fender electrics often have this arrangement, but it's far less common on 3+3 style headstocks.  And I'll show you why.

For what purpose do I wish to do this?  I've seen differing opinions, some of them strong.  And the person in that link has a point.  In any case, when the guitar nut is viewed as a dimensionless line, the string is only going in one direction:  either it goes over the nut and straight "down" to the tuner, or it goes over the nut and "left/down" or "right/down" to the tuner.  That's a fact.  But to my mind, that misses a couple of points:

1. Straight pull just seems like it ought to be better, facts be damned
2. I like how it looks
3. The argument fails to take into account the actual geometry of the guitar nut, which is a vertical slot cut into the nut material.  A string that goes straight "down" lays naturally in this slot.  A string that goes left or right as well angles down into the slot from the front edge of the nut, then makes another angle from the back of the nut slot to the tuner.

Anyhow I'm doing it.  If I screw this all up I'll simply saw off the headstock at the scarf joint and glue on another piece, or something.

First job is to determine the natural lie of the strings.  I haven't been able to figure out a good way of doing this, really.  I figure close is good enough for this cheap acoustic.

No, wait.  The first job is to plug up the four holes that will be moved.  I used 3/8" oak dowel glued in with that same hardcore two part epoxy I used to do the fiberglass layers on my electric.

Then I put tape across the last inch of the end of the headstock, put the bridge pins in place, made a loop in a piece of string, hung it around each of the bridge pins in turn and ran it through the correct slot in the nut, and eyeballed a line on the tip of the headstock.  When the lines were pretty close to evenly spaced, I figured they were pretty close to correct (proportional string spacing or not).

Then I used a little piece of brass tubing from the torch tip cleaner kit that was almost the same diameter as the wrapping portion of the tuner shafts to mark the desired locations of the new holes.  This is hard because each of these 3/8" holes will interrupt valuable grain in the headstock material, inevitably weakening it.  So I staggered the hole locations.  

Drilling simple holes when you don't have a drill press can be an adventure as well.  Drill bits wander from starter holes; verticality becomes an issue.  I solved the wandering problem by making a template from a piece of steel stock:

Yes, really.  Then I measured from the holes to the desired edge of the headstock based on providing enough clearance for the tuner buttons to rotate.  I then made a silly flowing profile and attacked it with a coping saw, because a tilt-back guitar headstock is not easily amenable to cutting on a bandsaw.  Nice filled holes, huh?  This guitar is looking better and better every second.  

There are a million little holes on the back of the headstock where the old tuner mounting screws were removed, and where I misplaced the new tuner locator pin holes a million times.  Since strength is an issue here, I'm going to fill all the small holes with raw epoxy puddles.  I guess that should be strong, unless it's not.  I have the option of finishing the edge and face of the headstock with veneer to cover  up all the mess, but in order to do that I'd have to take away native grain and that concerns me.  I think this is just going to be an ugly guitar.

Proportionately Cutting a Guitar Nut, Cheap and Naive

I ordered a 1/4" blank bone nut from StewMac and decided to make my own.  I'd never done that before.  I cut it to length with a hacksaw and to shape with 100 grit laid on 1/4" plate glass.  I've read that 3/16" of bearing area is sufficient.

I cut it roughly to height with the hacksaw as well.  Since I knew that the original nut was a bit high, I used the one to draw a line on the other, placed the new nut in the jaws of the vise with just the discard area sticking up, and chopped it flush.

I used a tiny hobby triangle file to start the slots for strings 1 and 6.  Then I was faced with the problem of spacing the rest of the strings.  This was fun.  I wanted to space the strings proportionately, which means that instead of being spaced evenly on center, they will be spaced evenly based on the distance between their edges.  First, I needed a jig:

I obviously made that, and it was obviously cheap.  I put six nuts on a small threaded rod and used them to enforce my desired string spacing.  This works best, I think, on a traditional 3+3 setup lacking straight string pull. - the horizontal break angles pull the string into the adjustment nuts.

Then I calculated thusly:

1. 1 and 29/64" between the high and the low strings =  1.453125
2. The total diameter of strings 2 through 4 = 0.114
3. The total space to be divided among the remaining five string gaps = 1.339125
4. The amount of space between each string = 0.267825
5. Multiplied by 64 to make it 64ths = 17.1408

I thus attempted to put 17/64" between every string - that means diameter to diameter or what have you.  That way thicker strings get their share and fingers get the same amount of space around each string.  Is the better?  Who can tell?  Measuring was hard with my eyes.  Around a year ago I noticed that I have trouble at close range with tiny little 64ths of an inch.  Luckily, I found this weird lens in the junk drawer of my tool chest:

It's badly scratched but it actually worked well for this task.  Once I had the spacing, and believe me that (for me at least) committing to a measurement is a real act of faith, I marked each side of each string with a pencil.  Not an ordinary pencil, but a pencil sharpened on a flat sheet of sandpaper to make a knife edge.  

Then, as I said, I started each slot with a hobby file of small size and triangular cross section.  This is nerve wracking in itself:  I couldn't commit a deep cut until I was sure the groove had landed exactly between the two bracket lines.  When I'd cut deep enough to just touch both lines, and that contact occurred at the same time, I had confirmation that I'd hit the center properly.

Then I finished the slotting with a cheap set of welder's torch tip cleaners, a trick I'd found in several places on the internet.  I am unable to make the exact citation, and I do not know who originally proposed this solution.

They look like that.  I just picked the one that looked next-size-up from my string using my untrusty eyeballs and my fingers (important).  The large ones were able to hold up to the filing pressure, while the small ones need to be supported by your fingers wherever you can hold them.  I settled on one finger from my free hand on the edge of the nut, and one free finger from my filing hand pushing down on the file right where it crossed the nut.  It worked.

My next task will be more outlandish:  straight pull conversion.

Fred Edge Dressing, Cheap

This fretboard is bound by a strip of black plastic.  I could have taken this opportunity to trim the frets to size and snip their tangs to preserve the binding, like you might for a good guitar.  But I chose to extend the fret slots through the binding and do it the easy way.

You can get special tools to allow you to hammer frets over the body of the guitar, but why spend the money on that when you have a large hammer that can also be used for other things?  That big one at the bottom:  you can reach through the soundhole and support the fretboard with it.  It helped that the fret slots were generous in width for the StewMac fret tangs.

I trim the fret ends with a regular end cutter, not a fancy luthier's model.  My whole goal is to avoid buying specialized tools.  When I cut, I push the cutter against the fretboard and then pull it back just a hair, to prevent the fret from getting levered out of its slot by the unsteadiness of my hand as I apply pressure to the cutter handles.  

Then I was left with a row of spikes on both sides of my fretboard.  When I built the neck for the electric, I simply ran a mill file freehand down the sides.  The worst that happened there were a hand cramp, a bloody nick, and the occasional ding on the headstock when I ran the file too far that way.  The acoustic presents one new problem, however:  freehanding it is impossible because the file would repeatedly hit the guitar body where the fretboard goes over it.  

So I made a tool that consists of two clamps holding a mill file to the edge of a board.  The clamps are heavy, so I arranged them in opposite directions.  The file descends only 1/8" below the face of the board, which is run along the fingerboard.  It was heavy as hell but worked perfectly.

The black plastic binding took some damage so I sanded it down with progressively finer grits of paper until I'd taken off the damaged finish material and plastic fuzz.  It's visible but doesn't interfere with function.

Fine Radius Adjustments on a Fender LSR Nut

The action on the low-E string of my LSR nut was a little high.  I think it's because the nut's supposed 9.5" radius doesn't match the fretboard's supposed 10" radius at the nut, or my alleged fret leveling job, which might very well have changed the effective radius of the neck.  Either way, the low string was way high.  I decided to explore a theory.  No pictures because my crappy old camera won't focus on anything so small.

No warranty, expressed or implied.  Proceed at your own risk.  Good luck.

Here's what I did to lower the action on a string.  Seems to have worked for me, except that this operation seems to have wrecked some of the springy retention ability of the retainer prongs.  I will have to be careful when changing strings forever more.  I think if I had removed the nut completely and taken the retainer finger assembly off in one piece, that might not have happened, but imagine what a pain in the ass that would have been!

1. Place the guitar on a nice smooth surface covered neatly in cloth.  The little ball bearings, once lost, will never be found again if they bounce on something hard.
2. Loosen the string and pull it aside into a neighboring string slot.
3. Pry the retainer prongs back toward the headstock a little.
4. Use a slightly-magnetic awl tip to draw out the two ball bearings.  Grab them between your pinched fingers before you lift them very high, and put them in a container.
5. Use a drill bit slightly smaller than the ball bearing cups to deepen the holes that hold the bearings.  Measure forty five times and cut twenty times.  Go a little at a time.  You can't go back.  How do you know where to put the holes?  I dunno.  I just leaned the bit into the corners ever so slightly and drilled.
6. Replace the bearings, replace the string, and tune to pitch.  If you are convinced you need to go deeper, do so.
7. Lather, rinse, repeat.

Here's what I did to widen the string slots on the LSR nut.  I'm using a set of very heavy strings (12's) and I've been worried that the low string was hitting the edges of the little exit slot.

1. Steps 1-4 above
2. Use the awl to pop out the little foam dampener on the headstock side of the nut, and place it with the ball bearings.
3. Sand away with a tiny rectangular file.  Don't wreck the retainer prongs.

Your mileage may vary, especially considering that I'm just making all of this up.

Acoustic Refret

First I had to get the fingerboard all flat. I've struggled with flatness before.  This time I think I did better. Below you see my cheap aluminum level with a layer of fabric carpet tape plus a layer of 220 grit paper.

1. I use a solvent to clean the old tape scum off the level
2. I put on the carpet tape.  It sticks like a beast so hold it at one end, line it up an inch off the opposite end, and lay it down easy.
3. I use a razor blade along the edge to cut the tape flush, then peel the backing.
4. I put on the paper in 11.5" strips, then use the razor the same way to cut that flush

I made sure the truss rod was loose all the way, then I sanded.  There was a high spot at the soundhole end of the fingerboard, and another longer one from fret 1.5 to about fret 11.  By the time I was done, all the fake black ebony stain had come off, and I'd taken enough wood off that the whole idea of putting on high frets to lower the action was nullified.  Way to think it through, kiddo.

Also excellent:  the nut, which is supposed to pop off easy, did in fact pop off easy, but it took some grain with it.  I'll have to flatten that surface with a file.

Here is the first several frets.  I didn't order enough fret wire because I messed up, and the next batch didn't arrive in time for the hurricane.

Acoustic Refret, Nut and Bridge Shave

I've got an 80's Harmony acoustic, given to me by my brother.  It has a terrible high action.  The neck doesn't seem messed up, and the soundboard isn't too bellied out.  I don't want to reset the neck because it's a bit of a big step that requires tools that would cost real money:  steam and all kinds of things.  I know I could slap something together from junk, but in my experience junk (and connecting junk to junk) costs real money.

So for my next project, I'm going to try to lower the action on this guitar - backwards:

• Put gigantor frets on it
• Redo the nut to compensate
• Shave the bridge
• Perhaps convert the bridge from an adjustable-height bridge, which seems to take up precious verticality, to a fixed height
• Put in a brass plate below the bridge plate to prevent the string ball ends from tearing up the soft wood down there.  StewMac wants $12 for this but I can make one for more like 20 cents.

Here's the old adjustable bridge:

 It won't go low enough.  I think I'll have to shave the bridge down too.  That will come after the refret, once I see the action I'm getting.

Here are the strips of feeler gauge I'm using to protect the very soft fretboard against the heel of my fret-removal chisels:

I don't have a fancy fret-removing end cutter that's ground down so the cutting edges are flush with the flat face. These chisels work beautifully.  I do guess that there's a slight outside chance of a truly horrifying accident, if one of the chisels comes loose, rides up the other chisel and unzips the flesh of my forearm.  That would suck.  But I didn't get the feeling that was likely to happen.  There's not a lot of force involved in this; the trick is getting a sharp edge under the metal/wood interface.

I'll be ordering fret wire and replacement blank nut and and bridge this week.