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Clamping cauls on Finished Guitars
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=52356		 Page 1 of 2
Author:  Colin North [ Thu Sep 12, 2019 3:25 am ]
Post subject:  Clamping cauls on Finished Guitars
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?
Author:  Greg Maxwell [ Thu Sep 12, 2019 6:58 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
I use a similar wedge covered in leather, smooth side out. Works great.
Author:  jfmckenna [ Thu Sep 12, 2019 7:16 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
I use a plywood caul with cork on it but also pad it with felt.
Author:  Chris Pile [ Thu Sep 12, 2019 8:20 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
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.
Author:  Michaeldc [ Thu Sep 12, 2019 8:31 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
Before I switched to a full body-on, I clamped the extension through the sound hole against the neck-block extension.
Author:  SteveSmith [ Thu Sep 12, 2019 8:55 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
I also clamp the extension through the sound hole.
Author:  Colin North [ Thu Sep 12, 2019 9:16 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
I also clamp the FB extension through the soundhole, but use more clamps above/behind the neck block before hand.
Author:  jfmckenna [ Thu Sep 12, 2019 9:44 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
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.
Author:  SteveSmith [ Thu Sep 12, 2019 10:11 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
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.
Author:  Colin North [ Thu Sep 12, 2019 11:10 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
jfmckenna wrote:
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.

And to protect the finish on the back of the neck block, if its finished? (which was the question)
Author:  J De Rocher [ Thu Sep 12, 2019 11:35 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
I clamp the extension through the sound hole too using two cam clamps. No other clamps.
Author:  Ken Lewis [ Thu Sep 12, 2019 12:10 pm ]
Post subject:  Re: Clamping cauls on Finished Guitars
What finish? Thinking it's still a bit soft. maybe?
I've used the wedge shaped caul as well without denting.
Author:  Colin North [ Thu Sep 12, 2019 1:00 pm ]
Post subject:  Re: Clamping cauls on Finished Guitars
Ken Lewis wrote:
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.
Author:  jfmckenna [ Thu Sep 12, 2019 1:20 pm ]
Post subject:  Re: Clamping cauls on Finished Guitars
Colin North wrote:
jfmckenna wrote:
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.

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

Post #2 above :D . 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.
Author:  Ken Lewis [ Thu Sep 12, 2019 1:38 pm ]
Post subject:  Re: Clamping cauls on Finished Guitars
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.
Author:  meddlingfool [ Thu Sep 12, 2019 2:10 pm ]
Post subject:  Re: Clamping cauls on Finished Guitars
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...
Author:  Clay S. [ Thu Sep 12, 2019 7:46 pm ]
Post subject:  Re: Clamping cauls on Finished Guitars
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.
Author:  Colin North [ Fri Sep 13, 2019 12:24 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
Clay S. wrote:
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.
Author:  Woodie G [ Fri Sep 13, 2019 7:12 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
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.
Author:  Colin North [ Fri Sep 13, 2019 8:00 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
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 bliss , so I have fill 'n'1 finish for drops fills. [:Y:]
Author:  Colin North [ Fri Sep 13, 2019 8:16 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
P.S. is that the nitrile rubber bonded gasket material?
Author:  Woodie G [ Fri Sep 13, 2019 11:34 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
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.
Author:  James Orr [ Fri Sep 13, 2019 12:14 pm ]
Post subject:  Re: Clamping cauls on Finished Guitars
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.
Author:  Clay S. [ Fri Sep 13, 2019 12:29 pm ]
Post subject:  Re: Clamping cauls on Finished Guitars
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.
Author:  jfmckenna [ Sat Sep 14, 2019 10:16 am ]
Post subject:  Re: Clamping cauls on Finished Guitars
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.

Image
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