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Yeah, those clamps do look like a better way to go. I'll eventually get some. It looks like my first bridge install is also going to be my first bridge removal. I'll be making a proper caul this weekend and see if I can fix it.

Guys, I really appreciate all of the help, advice, and comments.

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Mike Fields

One thing you might do before removal is see where a straightedge along the frets hits the bridge under tension vs. no string tension. That will give you a rough idea how much everything will move strung up.

The goal (assuming the fretboard exension has some drop off) is to have a straight edge just clear the bridge strung up. That usually means it has to clear the bridge by a greater amount with no tension. You can estimate that amount by how much the neck moves between no tension and full string tension.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

FINALLY, I'm finished with this one. I removed the bridge, installed another one using a proper caul, and actually got it playing really good. One thing I didn't notice until after I had gotten the second bridge on is that the neck is a little forward of where it should be. I told the owner about the neck problem and he said to do the best I could and he'll let the next owner worry about a neck reset. The string height at the 12th fret is 5/64" for the low E and 4/64" for the high E. Also, this is the Pro model and has a somewhat different body shape than a standard Hummingbird. It's supposed to have a different pickguard, but the owner wanted the one with the birds and flowers, so I had to do a bit of trimming to get it to fit. I really learned a lot and I'm sure I'll do better with the next one. Thanks for all of the help, guys.

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Mike Fields

What Arnt said but I use 5 of these. http://www.stewmac.com/Luthier_Tools/Ty ... lamps.html

I don't remember them being that expensive though. I guess nothing goes down in price.

I use the StewMac clamping caul on the bridge, 1 C-clamp in the center, with a 3/4" caul on the bridge plate. I have never had an issue. I always dry clamp it first and make sure that I have a good fit, with no gaps between the bridge and the top. I use index pins in the bridge, and use 2 long strips of masking tape to hold the StewMac caul in place while I am clamping. It keeps it from turning, or moving when I tighten the C-clamp. I place the tape so that it is easy to remove after clamping, to allow access for the glue clean up.

James

Nice clean work, I'm curious abut the bridge dimensions? This one looks big enough for twelve strings

Good eye, Clinchriver. I'm afraid that I had to make the bridge over-size to cover up the damage done during my first failed attempt at gluing on the bridge. Some day, a real guitar tech needs to get ahold of it, refinish the top, and put a proper sized bridge on it. It does sound good, though, and it's louder than my Taylor.

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Mike Fields

Oh my gosh you put the bridge on backwards!!!



If you have that guitar set up with that action and still have about 1/8th inch of saddle on a 3/8th inch thick bridge then you probably don't have any neck issues. That's good low action there.

Nice work on that bridge!

The Stewart MacDonald bridge clamp works well for clamping the center section of a bridge, but there are some technique changes versus those described in the Stewart MacDonald instruction sheet necessary for consistent, successful use. For the outer wings, two additional clamps and either an extended, full-width bridge plate caul or add-on outer internal caul blocks outside the legs of the X work much better than attempting to calibrate the clamping pressure with the bridge wing screws by eye. Further, any pressure applied on the bridge wing pads reduces the clamping pressure on the center section of the clamp, while adding two additional cam clamps adds to total glue line pressure. We would not attempt to use the SM bridge clamp without an interior, fitted caul of at least 18mm thickness, and - this is important - two clamps located over the cork pads of the main body of the clamp versus a single center clamp. Using that single center clamp - especially without a beefy interior caul - risks bowing the bridge, top, and plate.

We use 315g hot hide for all bridges, so we preheat the bridge itself to 130 degrees F to gain enough working time for the operation to be completed before the hide reaches gel temperature. We place the bridge, then clamp the center section using two aluminum Ibex/ShopFox clamps. Once the center is snugged down, we adjust the outer screws to bring the clamp pad in contact with the bridge wing, and the wings in contact with the top (we stop once we start seeing squeeze-out). We use mid-length cam clamps (6"-6-1/2" depth, depending on the maker) to clamp between the interior caul and outer screw handles...the screw handle works as an effective clamp pad outside the body and an 18mm plywood caul works well inside the body to clear the bracing.

To date, we've not seen any failures on the hundreds of bridges we've glued or reglued using this tool set and technique, and have not seen the type of body distortion mentioned in the thread when employing this modified approach to using the Stewart MacDonald tool. We've ordered one of the Jescar/Summit clamp assemblies to experiment with, but not because of any perceived deficiencies in the StewMac offering.

The picture below shows the clamping arrangements on a dreadnought and a 00; the corners of the cam clamps adjacent to the bar may have to be beveled back a bit to accommodate with very small sound holes or shallow bodies, and it helps to insert all clamps and cauls prior to glue-up, with the top padded with cork sheeting to avoid scratches or dents. After gluing, we store the bodies so as to minimize loads on the top due to the weight of the clamps and cauls - these bodies were stored leaning against a shop wall at about 20 degrees from vertical.

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

I'm not sure I understand that clamping arrangement.
To get pressure on the wings that way, don't you have to flex the top and/or inside caul up to the bridge? Why not just do away with the Stew Mac caul and clamp the wings directly?

The post was specifically with regard to the StewMac bridge clamp and how to use it correctly; the clamp can be used without risk of top distortion if the outer clamps are tightened only enough to bring them down to the correct registration following the inner clamps being torqued - applying more that that necessary to just close the wing joint runs the risk of distorting or cracking the top.

At some point, the joint has to be closed, and that is as much pressure as is applied to the wings before the independent outer clamps are applied. Whatever we are doing, it is apparently working well - no distortion, no change in measurements pre- and -post glue-up, and no bridge separations over the last 11 years with this approach and tool set. We hit our target string height every time, which seems like the real test of a clamping method.

Advantage? There's only one caul to position at glue-up, so handy for hot hide glue users that have to move quickly. Disadvantages are that the clamp is really not designed to do what it is advertised to do - it will not provide even pressure on the glue line if used as suggested by StewMac...hence, the difference in our usage technique. But I agree with your point - with the right cauls to address a sloped upper surface and/or wings, there is little or no difference in result between four independent clamps (assuming metal clamps on the inners) and the way we use the tool set. We just find it easier to move through a Martin-style bridge glue-up (radiused/curved upper surface) using the tool.

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

Great info, Woodie G! Thanks much!

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Mike Fields