Day 11: Finish Touchup
Once the peghead drilling and counterboring were complete, it was time to start drop-filling the lacquer and touchining up the reaired damage at the sixth string tuner hole. My goal is to avoid changing the appearance of this fine old guitar, so I set about working only in that restricted area.
First, the final leveling of the rosewood plug. I used a single edge razor blade with the ends protected with masking tape to scrape the plug to the level of the surrounding lacquer:
I did scuff about halfway through the lacquer in the immediate area because I'd be adding new stain and lacquer and I didn't want to end up with a raised lump after it was all polished out.
Freshly sanded or scraped rosewood has a habit of turning very dark with the addition of shellac or lacquer because the solvents cause the natural dark oils in the wood to bleed across the surface. To avoid having that happen, I sealed the plug with a "sizing" coat of thin hide glue:
Once the water evaporated and the hide glue was fully dry, I used my toothpick brush to dab on some retarder thinner to soften and amalgamate the damaged finish and to prepare it for the drop filling to come:
After letting the amalgamator do its job, I brushed a heavy coat of clear lacquer on the area:
Now, here's a tricky little bit. Once the lacquer was on, and before it began to dry, I took a tiny sharp pointed knife blade and scarred through the lacquer, hide glue and all to make dark lines, taking advantage of the rosewood's tendency to darken with the application of solvent:
That way, I was able to improve the grain and color match of the plug a bit.
Still working while the lacquer was tacky, I used a toothpick to add a few little streaks of brown stain - again to help blend the color and pattern:
Now, the neck will get put aside for a while for the lacquer fill to dry, and over the next few days, I'll add a bit more clear lacquer to build thickness in the broken areas.
Day 12: Making Another Small Tool
This is more of a homework assignment. I did it in the evening in my home shop where I do most of my metal work and machining. It's another of those "someday" items - a little press for inserting the Waverly tuner bushings in the counterbored peghead holes.
After milling a chunk of aluminum into a "C" shape, I drilled the top and tapped it for a press screw:
I wanted to use a 3/8" diameter brass screw, but as I looked around the shop I couldn't find one, so I chucked up a short brass rod and single-point threaded it, and turned the end to 1/4" diameter to fit inside the bushings.
Here's my little C-clamp press:
I got to thinking that if it's a tool that will be used around the shop often, it ought to have a built-in handle, so I looked around for an idea or two.
Then, I remembered I had brass balls (OK, calm down now). I used two of them, drilling 3/'16" holes and pressing them onto a 3/16" diameter steel rod stuck through the hole in the screw:
Done, and ready for the time when I install the tuners:
And, as always, "None Genuine Without This Brand" . . .
Day 13: The Bridge Plate
Here's a refresher look at the underside of the bridge plate. Notice the enlarged slots, particularly at the two bass string holes:
While it may look as though all six slots are munched out too much, four of them are only compressed a bit, and it's the shadows from the inside lighting that make it difficult to show that they are basically still OK.
TIme to introduce another special tool and technique. It's Dan Erlewine's brainchild, and, not surprisingly, marketed by Stewart MacDonald - the "Bridge Plate Saver." Really, a pair of tools, one of which, working from the outside, cuts a dome-shaped recess in the bridge plate, and the other of which cuts a mating plug in the drill press:
First I made up some plugs, using a slip of maple approximately the same thickness as the bridge plate:
Then, using the threaded block on top of the guitar, I twisted the tool until it pulled upward and ate the appropriate hole in the bridge plate:
Here's the first one - nice and neat:
The second one went just as well, and I slathered up the two plugs with some nice hide glue, stuck them in place and got ready to clamp up. Before applying the clamp, I dropped in some small pieces of maple to finish filling the slot from above. Probably, it wasn't a necessary move, but it was convenient, so I went for it:
And, as usual, a hard flat plate on top, protected with waxed paper:
Day 14: The Bridge Plate, Continued
Next day when the glue was dry, I took off the clamps, and got out the bottle of thin viscosity cyanoacrylate. This modern adhesive can do some stuff that none of the old time glues can, so I don't forget I have it on hand when just the right job comes along. In this situation, I'm using it to reinforce the crushed wood fibers of the bridge plate against future string ball damage.
Simple enough, I simply mopped the iniside of holes, and the bridge plate beneath with a swab dunked in cyanoacrylate:
The thin viscosity super glue wicks in to all the exposed pores and micro cracks, filling the voids and catalyzing into a solid acrylic that's amazingly strong and tough. Just the thing to resist the pull of those nasty little string balls. The treatment will keep the slightly crushed slots in good shape for years to come. And, once I have the bridge in place, and drill and slot the remaining holes, I'll give them the same preventive treatment.
A look inside reveals the flow of cyanoacrylate, and the two patched bridge pin holes:
The glue looks a bit sloppy, and the repair patches are somewhat uneven in height.
"All right - send in Robo Sander!"
Here it is, my spin sander, version 2.0:
This one has a clear acrylic body, so you can see the working bits. It's a quartet of rare earth magnets mounted in an aluminum disc, supported on a shaft and ball bearing arrangement that's totally enclosed in acrylic. Outboard, there's a second unit with four magnets, and discs of "Dragon Skin" abrasive - steel sheets with carbide bits on one side.
Because the housing doesn't rotate at all, there's no chance of scratching delicate finishes as the inner disc rotates at 600 RPM on the high gear setting of my cordless screwdriver:
As I hold the outer unit up against the top of the guitar, the inner one is attracted to it, and it rotates in synch with the driven magnetic disc, sanding the bridge plate flat and level:
Now the bridge plate is basically good as new - without replacement. Thanks, Dan!
Day 15: Top Crack Repair
If you go back to Day 1, you can see that little crack by the edge of the fingerboard. Being as close to the board as it is, the crack isn't all that obvious when you take a casual look at the guitar. But, it is an old, dirty little crack, so I thought I'd try to clean it up a bit before gluing and reinforcing it.
A number of years ago, I learned about the use of deionized water from Joe Grubaugh, a premier violin maker and restorer who's shop is in Petaluma, about an hour and a half from mine. He described the stuff as being so "hungry" for ions that it can attract and wash away stain and dirt without adding any detergent, bleach or other contaminant to an old crack like this one.
I called a chemical supply house that specializes in providing exotic water to local "clean" industry, and by luck, talked to a really down-to-earth expert who clued me in on an important bit. He said that if I bought their $50.00/gallon deionized water, I'd get a certified pure product, but it would stay deionized only a relatively short number of days after opening. He then went on to hand me a nice little surprise. He said that the deionized water I can get for 39 cents a gallon at the supermarket vending machine was really close to being as good for my use as the stuff he sells.
Well, after some consideration, I chose the local brew.
And, anytime I need good deionized water, I take a quick hike down the street with a jug, knowing that the stuff I'll be using is better than the industrial kind I'd have had sitting around the shop. . .
Pure water is a poor conductor of electricity because of the lack of ions. Regular tap water varies quite a bit, and local Palo Alto water comes from Sierra snow melt and is free enough of impurities that we use it in steam irons and car batteries.
Compared with our nice tap water, the supermarket deionized stuff is only about 10% as conductive:
I taped the probes together to maintain the spacing and dunked both in to the water all the way so the readings would be reasonably comparative.
Time to wash up.
I filled a clean styro cup with deionized water and dispensed it with a polyethylene pipette, dripping it on the crack, and allowing it to run downhill toward the neck block. I had the guitar body supported at about a thirty degree angle from horizontal, so the water would run in a controllable stream and be soaked up by a wad of rags below:
As the water ran along the crack, I scrubbed the crack with a really fine synthetic bristle artist brush. The bristles of this brush are slender and pointed, so they work really well without injuring the wood fibers.
After about 45 minutes, I'd run through around a pint of water, and I could see the crack becoming a bit cleaner. And, after the water dried, it looked as though the dirt was basically all gone. The crack is still visible of course, because it has width and depth, so there are shadows:
I made up a small diamond shaped reinforcement cleat, clamped and glued it in place:
I also worked a bit of my most transparent hide glue into the crack before applying the clamp. I don't think there will be much if any touchup of the lacquer needed here.
Viewed from the inside, the patch is small and unobtrusive, but it will keep the crack from becoming nasty, I think:
Day 16: The New Bridge
Today's the day to make that much needed new bridge. Most of the time, I'd rather make and install the appropriate height bridge before setting the neck angle. Of course, it's a matter of geometry, so the neck angle would be the same in relation to the top of the guitar whether there was a bridge in place or not. But, most of my neck resetting work is on guitars that already have the appropriate height bridge, so I'd rather set the bridge first, and then adjust the neck. So, today's excercise is making and gluing the bridge.
Really good ebony is getting harder to find every year, and recently, we've been able to buy some fine African ebony that's as good as any I've seen. It's not cheap, but then what is these days?
Whenever possible, I try to get "bow frog quality" ebony. Violin bow makers are the most insanely picky about the quality of the ebony they use, mostly because they use such tiny pieces they can afford to get the best of the best of the best. They insist on absolutely black ebony with the virtually invisible pores, and those must be completely filled with resin. In fact, that stuff looks about like Bakelite or Micarta when it is polished. If you look closely at some of the venerable old Martin guitars, you see some of that quailty ebony there, too.
Last year I visited an importer and picked out enough for, I'd guess, five years' worth of bridges at the rate we make them these days. Those pieces went into our upstairs wood storage area, and we're likely to get to using it in about 2020 or so. I suppose that makes us ebony independent until 2025. That's the way we've always worked at Gryphon, trying to stay well ahead of need for supplies that might get cut off at any time without notice.
Later on, I'll be making an ivory nut and saddle for this guitar, and I'll be using ivory that I bought before there was any ban or restriction on elephant ivory. Since that time, we have kept our use of ivory to important restorations. For the record, I simply have no patience at all for those who might think or suggest that it has a benefit for tone over good hard bone. In fact, I prefer unbleached bone for longevity, appearance, and tone, both for nuts and saddles. But that's not the point when we're doing a serious restoration
For those looking for ivory, please understand that we don't have any at all to spare for any reason or project. That said, there is a good source of legal elephant ivory, and David Warther can serve your needs: http://www.ivorybuyer.com
Rant over, I hope. . .
Here's the ebony bridge "blank" I'll use:
We make quite a few Martin style guitar bridges at Gryphon, and, since each one is slightly different, we like to start with an oversize rectangular piece so we can match the contours of the original as needed. I machine these blanks with the proper 1" radius scoop at the ends, to give us a head start in carving.Because vintage Martin bridges were made by hand, they don't all have exactly the same footprint, and, in fact, they are not quite symmetrical, either. To get an exact pattern, I cover the bottom of the original bridge with tape, and use a razor blade to trim it:
After cutting the holes as well, I have a nice pattern I can stick on the bottom of the new bridge blank, and thereby transfer the shape directly:
I try to work from the back side as much as possible to maintain hole alignment, so I'll actually set up and drill the bridge from the back.
Here's a simple bridge drilling fixture I made up a few years ago:
There are four rows of holes for the four most common bridge pin spacing on Martin guitars. (LMI used this one as the prototype for the one they have in their catalog, by the way.)
With the bridge clamped into the fixture, aligned so the holes in the tape matched up with the 2-5/16" spacing of the jig, I drilled through the blank:
Because the blank was about 1/8" over the final thickness I didn't worry about tearout as the drill bit went through.So far, so good:
Rough cutting on the band saw, I tried to keep within about 1/16" of the tape pattern:
Then I was able to sand "offhand" on the upper roller of our 6" belt sander to establish the outline right up to the edge of the tape:
And, using a little hand crank sander, I was able get in close safely and run right up to the tape's edge:
Bridge day, continued . . .