Official Luthiers Forum!

I read once that some of the charm and what made the old classical guitars great was subtle changes in the tops thickness due to using hand planes as opposed to today's thickness sanders that make everything even and perfect. Also that using a blade to cut the cells of the wood fiber actually makes the wood stiffer for any given thickness as opposed to the striated surface that a sander will impart.

Probably just a bunch of nonsense that makes sense on paper only but it might make ya feel better

Both of those could very well be valid but don't really apply to my building technique. Even without thickness planing, there is variation in my top thicknesses because I do a fair amount of sanding after the binding is on. Some of that sanding is trying to selectively thin areas in a hope to learn how to get the sound I want. Some of it is because I need to sand

I can see that a given thickness would be less stiff if it were sanded rather than planed since it effectively would have a bunch of grooves the depth of the grit on both sides. Those grooves would reduce the stiffness but not the thickness measurement. How much of an effect, I can't say but it is way below my expertise to be able to take this into account. Besides, I still have to sand anyway. . .

Someday, maybe I'll be good enough at woodworking and guitar making for this to be on my radar but I have a lot of work to do to get there.

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

I saw a similar post here about setting cap irons a year ago. I tried it and am pleased with the results. I finally see the benefit of the cap iron. Now , at times, I set it at 1/32"

I'm a little skeptical that the imperfections are what made the guitars great, but I don't think they hurt things as much as some people believe. Most of the old makers couldn't charge exorbitant prices for their work so spent less time "polishing" the parts you didn't see. I think the perfectionism we see from some makers today may actually hurt more than help. In their effort to make the instrument look perfect they may be "polishing" the sound out of it.

What I tell myself:

"All these little variations and beauty marks just add to the small-shop charm of my work."

What the guys in the shop tell me:

Boss: "It's not like there's a line for the sharpening bench. Get your tools sharp and clean this (stuff) up."

Mr. Morelli: "You COULD choose to leave it that way, but you could also choose to fix it. Choose wisely."

It is considered bad form to throw things in the shop, but just once...

On the topic of wisdom versus whizdumb:

We had a customer over that went on for 30 minutes about how imperfections on plates, braces, bridge plate, and linings will 'trip' sound waves as they bounce around the interior, and that keeping the spacing of kerfs at a certain value would prevent wolf-notes caused by those itty-bitty higher-frequency sound waves from getting lodged between the dentils and 'expending all their mojo' trying to get out. He had heard this from several builders, including the constructor of the guitar we were fixing, so considered it to be gospel truth.

Mr. Morelli pause from his work and - with his characteristic eye for absurdity - mentioned that the wavelength of sound at 50 Hz is just under 7m, so speculated that the best builders fold those longer wavelength sound waves very neatly using the Marie Kondo method. There was a faint 'whoosh' as this comment passed well over the customer's head.

_________________
For the times they are a changin'

- Bob Dylan

"Mr. Morelli pause from his work and - with his characteristic eye for absurdity - mentioned that the wavelength of sound at 50 Hz is just under 7m, so speculated that the best builders fold those longer wavelength sound waves very neatly using the Marie Kondo method. There was a faint 'whoosh' as this comment passed well over the customer's head."




Woodie,
If eliminating a small chisel gouge that isn't seen except with a mirror means sanding a plate thinner than it should be, or using too little glue so there is no chance a small amount of squeeze out can be found, then maybe throwing something (if only a tantrum) is in order.
I try not to be too sloppy building my instruments, but casual observation with a mirror of the interior with show that glue was used in their construction.

I used to carefully sand and scrape the underside of my tops so that they looked "perfect". I got over it. I don't do sloppy work but I sure don't waste a ton of time making the unseen places pretty, I leave my braces with a rectangular cross section too although I do sand them smooth.

_________________
Steve Smith
"Music is what feelings sound like"

Yeah that's another point along those lines. Some makers today build the inside of the guitars to look like doll houses when leaving that saw mark behind may have just been the right thing Or as Hesh likes to call the glue drips in old Gibsons - Tone Snot hahahahha!

I think the boss's notion of the right level of rectitude is more of a 'no excuses' interior finish...as in no need to make them when another builder takes a peak. This seems to me to be about as clean and well groomed as the average 1930's era Martin. We see more than a few custom built instruments that are at the extremes, though - some with better finishes on the interior than exterior, and others that are a dog's breakfast with back grafts and lining work that look like a preschooler was turned loose in the shop.

Looking at the 50th Anniversary D-35 that came in with failing bridge (heavily torrified tops seem to have a habit of shedding Titebond), I was surprised that the back grafts were left square-edged as laser cut. I know Martin's radiused graft is as much the exception as the rule, but the instrument left me with a feeling of being a little unfinished. Intellectually, I know that radiusing those two serpentine strips of cross-grain spruce by hand would add another 20 minutes to what is already a 12 or 13 hour hands-on number for the guitar, but I found myself wanting to grab a sanding block and get to work.

_________________
For the times they are a changin'

- Bob Dylan

What glue do you use for bridges on Torrified tops? I recently experimented with HHG and the results were less then positive so I used TB on these two current ones I am building. I used Fish for the bracing as was recommended by many here but am weary of using it on the bridge. My guess is that you need a very slow curing water base glue to take it's time to sink into the hydrophobic torrified wood. Titebond extend maybe? Or even dilute TB?

I doubt Martin hand planes back grafts (even that would only be a five minute job). Lasers seem to be the new toy in the wood shop so they are seeing what they can make it do rather than looking at the end result.

Today I'm reconverting an Irish castle wheel someone had turned into a corner shelf. Luckily they kept the flyer and spinning assembly as a decorative element. Unluckily they hacked it up a bit so they could plug it in to the distaff carrier. It had belonged to an older gentleman's great grandmother who used it to spin yarn. He had stored it in the attic for 57 years. Neither his children, nor grandchildren wanted it, so it hit the online marketplace.

315g hhg for torrified tops.

_________________
For the times they are a changin'

- Bob Dylan

From what I can see, torrified wood has intrinsically low surface energy. This means that, to the extent that the strength of the glue line is chemical, it's prone to produce a poor glue joint. It's easy to test this: spritz it with a light most of water and see if it beads up. If it does, the surface energy is low. The remedy for this is to work the surface just before gluing it to raise the surface energy. According to the Forest Products lab you get a better joint on 'normal' wood if you glue within 15 minutes of working the surface. From what I've seen of heat-treated wood and 'fossil' ivory, you've probably got an even shorter window. I used 215 gm HHG on a mammoth ivory bridge bridge a few years back. The hand-out that came with the blank recommended Titebond, but scraping the warmed up bridge just before slapping on some nice fresh glue seems to have worked: no complaints from the customer.

What we've seen on highly torrified wood is that - even after good prep - the surface is somewhat hydrophobic, so prep as Mr. Carruth described seems like one way to ensure a long-lasting joint. We know of at least one major manufacturer that has forsworn use of the highest levels of torrification until they identify a glue and glue-up protocol that ensures a consistent result, and are seeing some issues with instruments glued with their normal aliphatic resin-based adhesive and process. It would seem like adhesive use for bracing, bridge patch, and closing the body would be subject to the same concerns when using those tops.

The protocol we use for 315g bridge glue-up:

- Wear clean nitrile gloves for prep and glue-up to minimize contamination of joint during prep and glue-up
- Mix fresh 315g hhg (we use distilled water and a slightly drier mix than for 192g)
- Sand bottom of bridge on P80 radius plate, then immediately heat to 160 deg F (place bridge in foil envelop in 160 deg F oven or warm on plate warmer double-wrapped in foil/on foil sheet and tented with additional sheet of foil; turn over halfway through what is usually a 15 minute warm-up on on our Salton plate warmer. A properly calibrated non-contact thermometer is used to sense temp.
- Prep the already-cleaned up bridge patch with fresh scraper
- When bridge is at temp, use razor blade scraper to remove any possible surface contamination or resin bleed from underside of bridge (quick, light scrape)
- Apply 145 deg F 315 hhg to both surfaces
- Immediately close the joint and clamp
- Clean up squeeze-out and leave clamped for 6 hours minimum (overnight seems ideal)

The thermal mass of the bridge and 160 deg F temp ensures the glue applied to the bridge patch will remelt and allow the joint to be tightly closed even in a relatively cool winter shop, although we have used portable electric heaters to create a warmer work environment in the depths of winter.

_________________
For the times they are a changin'

- Bob Dylan

On further reflection, use of HHG may be an ecosystem issue for some builders, which is to say: unless the rest of the work flow is built around HHG as a primary adhesive, use for just a few tasks may seem very cumbersome. Because we use HHG for most instrument glue-up tasks, and always have the glue pot ready to go during normal shop operations, a lot of the prep work is a already built into the work flow, the remaining job-specific tools are handy (foil, plate heater, etc.), and the PITA factor is minimal.

There is also the initial learning curve associated with HHG...as children in kindergarten, we all learned to stick paper together with room-temperature adhesives like Elmer's Glue-All and school pastes. For better stick, we put glue or pastes on both pieces of paper and applied a little pressure (and for Billy Timkins, some semi-solid nasal mucus, if memory serves). Titebond and fish use in luthiery builds on this early childhood learning, as well as later adhesive use in middle or high school shop & home economy classes, etc., so there is very little to learn in terms of additional technique. HHG, on the other hand, requires techniques and patterns of use which are outside of normal experience with daily-use adhesives - more judgement is needed in mixing the stuff up, more cautions are associated with use (not too hit; not too cold, etc.), and more infrastructure necessary to handle normal use (e.g., shop 'fridge; glue pot, distilled water supply, heat gun or hot plate...).

In summary, I suspect that HHG is something that a builder commits to - versus experiments with use of - in the shop.

_________________
For the times they are a changin'

- Bob Dylan

I never tried measuring the distance of the cap iron, but thought I would today since I was taking a skim off the workbench I'm making.
I set it beyond 1/64" this time and have gone even further with the no.4 on many occasions.
Becoming easier now that my new stone is getting flatter.
1/64" still gives a narrow shaving if the irons not too deep.
Im not talking super wispy shavings either, but thinner than the other photo I posted.
I don't think I can get a clear photo of the distance next to the 64th markings on the ruler
All I can get is the shine which looks far larger in the photos,
Its either that or the cap iron without seeing the cutter.

Just thought I'd mention that since you folks would be needing to do the same with some of the stuff I've seen here.
Hope your all keeping well folks
Tom