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For a mortice and tenon bolt on neck I've been using a 1/8" cork lined wedge behind the neck block to lightly clamp the FB extension down while gluing and bolting it on.
This is marking the finish, several small dents clearly visible on a gloss finish.
What do others use for the contact points when clamping on a guitar, especially on a recently finished one?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I use a similar wedge covered in leather, smooth side out. Works great.

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It will probably be alright.

I use a plywood caul with cork on it but also pad it with felt.

Pads are rectangles cut from Masonite, the felt is from an old cowboy hat. I use double stick tape to hold the felt to the Masonite. Been using the same cauls for decades with no problems. If I get Titebond on the felt, it washes off. Superglue - turn the felt over or slice it off with an Exacto blade.

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"Act your age, not your shoe size" - Prince

Before I switched to a full body-on, I clamped the extension through the sound hole against the neck-block extension.

I also clamp the extension through the sound hole.

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Steve Smith
"Music is what feelings sound like"

I also clamp the FB extension through the soundhole, but use more clamps above/behind the neck block before hand.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I use a long caul so that it transverses the 14th (or 12th) fret to body joint. One clamp through the sound hole and one on the neck block back of the guitar. Everything clamped tight and dead flat.

Thinking about this some more, when I put on the neck and glue the dovetail I do put a clamp between the fretboard and the back under the neck block. I just use one of those 12" Irwin squeeze clamps with the yellow rubber pads, have not had any finish damage to date.

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Steve Smith
"Music is what feelings sound like"

And to protect the finish on the back of the neck block, if its finished? (which was the question)

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I clamp the extension through the sound hole too using two cam clamps. No other clamps.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

What finish? Thinking it's still a bit soft. maybe?
I've used the wedge shaped caul as well without denting.

Enduro Var, and I think it was still a bit soft, 16 days after spraying.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Post #2 above . I use the same cork lined caul you do only I line it with felt. So there is felt on top of the cork on top of the plywood caul.

I mostly do French Polish finishes so it definitely needs it.

I would think 16 days should be long enough for cure/hardening, unless....
the guitar was at ambient humidity for those 16 days. I've seen, over the years, that waterbornes in general
will remain soft for quite a while when the humidity is up a tad. I haven't used a waterborne on guitars... yet, though.

I just use a polish cloth folded in four and a scrap block for the neck, and a soundhole clamp/caul for the extension. Sometimes you'll get fabric imprint but it usually buffs out without having to sand...

I use pieces of formica about 2 inches by 3 inches between the clamp and finish. The smooth hard finish of the formica and larger footprint seem to distribute the pressure over a larger area and are less likely to mar the finish.

Are you using the 50 thou thick laminate itself so it conforms to the curve of the back?
And it doesn't slip on the slope of the neck block end of the back when pressure is being applied?
Interesting approach.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Verified the hard way - Enduro-Var is a 21 day cure. Attempting to sand and buff or do assembly prior to that risks burn-through at buffing and printing. While we can push instrument lacquer to dry faster in the drying box, Enduro-Var needs time to crosslink and firm up. Fully cured, the finish is very tough and fun to buff out.

We use several facings for cauls and other fixtures. Staples 1/8" cork tiles work well,, but the best cork sheet material we've found is the cork/rubber composite engine gasket material similar to the facings on Klemmsia cam clamp jaws - available in 1/16" and 1/8" thicknesses. Saddle leather is a good choice as well, and we use it to line vise jaws on the big bench and on the older repair vise (the others have urethane sheet jaw facings.

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A constellation only takes shape when one maps the whole.
- Beth Brower

Advice and suggestion much appreciated Woodie.
These were buffed, easily, at 7 days.
Normally I would just have put them aside and not assemble until 21 days at least, but....
I am entered in a show starting tomorrow (booked this past March) hence the early assembly.
And we've recently become lucky enough to be able to buy GluBoost in UK , so I have fill 'n'1 finish for drops fills.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

P.S. is that the nitrile rubber bonded gasket material?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Good luck at the show! Wonderful that Enduro-Var patches so well with CA.

Also - yes - cork gasket material seems to be a nitrile rubber/granular cork composite. Tough stuff that is non-marking from what we have seen.

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A constellation only takes shape when one maps the whole.
- Beth Brower

Another option is closed cell foam. I use an adhesive-backed close cell foam called "ensolite" in my car for sound treatment purposes (isolating panels and vibration control), but it would be great in clamping solutions as well. A 54" x 36" yard is inexpensive. Super easy to apply thanks to the backing.

Hi Colin,
It is the thicker "horizontal grade" laminate typically used on countertops. I acquired a couple of outdated "chains" that have small sample pieces of the patterns and colors of the laminate on offer. They update the offerings and send new chains so I use the old ones as clamping cauls. The clamp itself usually has a small rubber caul on it that will grip to the unfinished side of the formica enough to hold it in place over the neck block or edge of the guitar. The formica is just there to spread the load over a wider area than the small face of the clamp and the smooth surface doesn't mar the finish.

Since I just happen to do this yesterday I thought I'd take a pic. That's french polish and using the felt pad it left no mark.