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This post is pretty much unrelated to the OP but I'll throw it out there anyway. With regard to radius dishes, they do not guarantee a perfect radius matching that of the dish. I'm sure most know this but some newer people might not realize this. If you sand your braces to perfectly match the radius of the dish it will not match the radius of the dish with the top sandwiched between it. In order to have the top match the radius of the dish and then have properly dimensioned braces glued to it, the braces would technically need to have a slightly tighter radius. IMHO none of that matters since the difference is very small and wood being wood will move anyway. In fact, I care so little about it that I use an adjustable radius dish which doesn't technically produce a true radius (but close enough for me).

This small variation in radius is so small that mentioning it is mostly academic. I bring it up because if we are worried about the difference between a pre-radiused sanding board and the top itself then go on tho have our goal be fit with finger pressure we are fooling ourselves. Either one is surely to be close enough. The bridge is likely to be stiffer than the top and bracing in that area; I think this is where Frank Ford's method of clamping really well shines.

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Bryan Bear PMoMC

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

To each his/her own -- but I know that many (perhaps thousands) of bridges have been glue to sound boards successfully and permanently using the methods and style clamp shown below. When one takes the time the sanding method produces a conforming glue surface and the clamp yields uniform glue squeeze all the way around -- plus this style of clamp makes for easy clean up. The clamp is similar to the aluminum Charles Fox unit, same principle -- cauls/spacers under the end bolts are important so clamping force is distributed on the wings.

I agree with something mentioned above -- I believe a pristine, clean surface, one that has been masked rather than scrapped, has a greater chance for a perfect bond.

http://www.kennethmichaelguitars.com/bridgeprep.html

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Ken Cierp

http://www.kennethmichaelguitars.com/

Sure but some of you guys, not you Wud, might complain that Stew-Mac is too expensive when those of us who use the hatchet every day would disagree.... What do you think happened to Dan's hair......

Hey Craig - a couple of comments for you if I may please.

No radiused cauls although we have used them in special circumstances. An old instrument with a profound radius for example might get a slightly radiused caul.

When I was building my cauls were radiused to match the top and back. I never understood the logic of radiusing the top and then smashing a flat bridge on it.... I also radiused my bridge plates.

I've also used flexible cauls with an ever so slight amount of flex in them to conform to the top. I also always wanted to make a "kerfed caul" out of say teflon for glue resistance that would flex a bit too making it a bit more universal.

Regarding masking pin and UST holes we don't do it. Instead the glue gets in the holes as you would expect and imagine which is not a bad thing on some older instruments where the pin holes are worn anyway. Helps to firm up these splintered holes.

After the clamp is removed I chuck a 3/16th" brad point bit in my Festool drill and redrill the pin holes, different bit for the UST. The pin holes are then reamed with a 5 degree reamer and the pins are fit as well. This is also an opportunity to fit the pins better than they were prior to removing the bridge as well.

This has been my experience as well. Radius dishes are a guide but what the actual radius will be if you don't brace it to be as strong as the George Washington bridge.... will vary. This is also why there is no magic number for neck angles, preradiusing bridges, etc. The fitting is up to us.

Nice write up Ken, thanks for posting it. I see no issues with this method either except with HHG use. May be a bit of a heart attack waiting to happen getting everything in place, wing nuts secured, etc. in say 15 seconds but with Titebond it should work fine. It might now be either since you do this all of the time and I have never done this method. Maybe comment on how long it takes to get the clamp secured in place please?

You know though regarding the millions of guitars remark as true as this is it is also telling in that some things that work well on new, everything is perfect, construction can be problematic on an old, torn up top and warped bridge. Builders have the luxury of well prepared surfaces where repair pukes have to do the well preparing.... ourselves.

When I was building I used Friskit film and that worked well. I would add though after removing the film and prior to gluing, within say half an hour or less do some quick scrapes with a single edged razor blade to both the top and the bridge bottom. This will help remove the debris that we can't see and damaged cells from the abrasive use and make the joint even better. It's a joint energy thing.

Yeah -- I don't know about "millions" of guitars either, but I think thousands may be representative based on reads/hits sales etc. None the less I should have indicated new work -- I totally bow out to you masters of repair -- that is not my thing.

I've used liquid mask, pretty cool, but the slightly under-size tape mask works for me. I saw that at the Martin Factory. Today I think they actually route off the finish under the bridge which is pretty flat to begin since their braces are contoured a mere 52'. Not sure if its mentioned in this thread but I also sand a very slight bevel along the perimeter of the bridge on the glued side -- a little insurance that there will be no interference with the finish coatings on the sound board.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Hey Ken - Another approach to that bevel and the ledge of the finish is to use one of these below. It's completely adjustable and can be set for say a .003" deep route and perhaps .005" inset making a little ledge that sits on the finish but the real value is that the entire gluing area where the finish is cleared has direct wood to wood contact.

Traditionally bridges are just slapped over the finish ledge which if you think about it means that the wood to wood contact actually ends some distance from the cleared finish edge since the bridge is spanning the ledge. The thicker the finish the worse the wood to wood contact...

As far as I know this is a Bill Collings idea and done on Collings guitars. We do it too with great results. One criticism that has been levied before on the forum was that this would make a bridge harder to get the spatula under it when it's time to remove the bridge. It's usually the case though that when it's time to remove a bridge it's already started lifting somewhere anyway.

On the cosmetic front if done well the bridge sits tight on the finish for a perfect look and the finish is tucked under the bridge making for a very neat installation.

Thank you -- I like that a lot!!

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Ken Cierp

http://www.kennethmichaelguitars.com/

Thanks Hesh,
I do the same as you regarding holes in the bridge with my clamping method.
I was curious about what those who use vacuum clamps do.
Looks like thry just tape over the holes.

Thanks again

I use a razor blade to scrape a little clearance groove around the perimeter of the bridge. This accomplishes the same thing as the router shown above and allows the bridge to sit down on the top as described above by Hesh.

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Jim Watts
http://jameswattsguitars.com