Official Luthiers Forum!

Just a new idea, probably not new.... just so bad no one has chased it.
But.....
For bridge clamping... why not have a caul with threaded rods that would fit UP through the pin holes and come out the top of the bridge. On the top a caul that fits over the rods and tightens down the top of the bridge with wing nuts?

Peace
-B


Sent from my iPhone using Tapatalk Pro

People do it all the time. I've done several that way. I am moving away from it, for a few reasons. First, I don't like having glue dribble down into the string holes. For new builds, I would rather only start (but not finish) the string holes in the bridge, glue the bridge down, then finish drilling the holes after gluing. It is less messy that way, and less prone to gluing a caul inside the guitar. Also, I have felt the need to focus more on getting the wings tight to the top, and using three clamps (one in the middle) is the way to go for that. But the bolt method works fine for lots of folks.

I wouldn't say it's a bad idea. I would be interested in trying something like that.
The two biggest challenges I see is keeping glue out of the threads of the bolts, and getting enough torque on a bolt/wingnut that can be no bigger than 3/16".
I don't foresee using the bolt method myself any time soon, mostly because I already have bridge clamps that work just fine, and avoid the above problems.

LMI sells one like that and has since the 90's. Charles Fox designed it. I don't like drilling the pin holes before gluing the bridge so I never used it. I suppose it might have a place in repairs.

http://www.lmii.com/products/tools-serv ... dge-clamps

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

B my friend they've been around a long time and they work fine with longer open time glues. Ken C. who is a member here makes them too.

Many of us especially those of us in the trade who do this professionally are expected to be tooled up and well versed in the use of HHG.

IME and IMO HHG is the superior glue for bridges because it won't cold creep AND it dries crystalline hard encouraging vibrational transfer. It's also serviceable in that we can get it to release and we can even reactivate it 50 years later...... And if that don't do it for ya customers who read the BS on forums ask for it and want it. Even Martin's "Authentic" series uses HHG because many of the most iconic and valuable guitars of all time used HHG.

One of the requirements of HHG is having the clamps in place and snugged down quickly, under a minute, we shoot for ten seconds. This kind of clamp is not conducive to doing this.

There are work arounds, a "hot room" like the violin people use working in their underwear could work but is not all that desirable for a multi person shop or a business that encourages A-list customers to just show up and walk in when ever they want...... Heat lamps, preheating parts all help with HHG but ultimately a clamp that can be prepositioned and has minimal things to crank is the most HHG friendly.

The through the pin hole clamps do work well with long open time glues.

I fall into the category of too inexperienced to use HHG because of the small time window:)
At least for now



Sent from my iPhone using Tapatalk Pro

Haha yea that’s it.
I knew it was probably already a “thing”


Sent from my iPhone using Tapatalk Pro

I think it is an idea that has potential and is worth pursuing. The Fox design is different. The fox clamp requires you wing nut from inside the guitar rather than from the top.

"The two biggest challenges I see is keeping glue out of the threads of the bolts, and getting enough torque on a bolt/wingnut that can be no bigger than 3/16""

The first problem could be solved by using bolts that are only threaded part way up, the second problem might call for using threaded knobs. A 3/16th rod is all I use for a truss rod - you can put quite a bit of tension on something that diameter.
http://www.grainger.com/product/KIPP-Mi ... =IDPPLAREC
The upper caul could be shaped to put pressure on the wings first and then the center. Having the lower bridge clamp in place, dropping the bridge in place, then the top caul, and tightening the knobs could be done in under a minute. Clean up around the bridge would be unimpeded by clamps.

B just be aware that we have a bad habit, me included of making HHG sound difficult to use. It's not and in some ways it's pretty easy. Just want to leave you with the idea that HHG is not difficult to use and the earlier you start the sooner you will wonder why you weren't using it all along.

One other thought... use UHMW polyethelene (slippery plastic) for the inside caul to minimize sticking problems.

I started using this bridge clamp about six years ago and all the bridges are still where I put them on the guitars.

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

I’m no expert but I used a plastic caul inside the guitar and two 3/16” bolts threaded through the inside caul and the 2 holes pre-drilled through the guitar top. I used HHG (for the first time). Since the inside caul and bolts were already in place before I ever touched the glue I was able to drop the pre-drilled bridge onto the bolts, an outside caul on top of that, and snug it down with wing nuts in well under a minute. It was really pretty easy.

My only issue was cleaning up the squeeze out. I wasn’t well prepared for that but it didn’t turn out too bad.

As someone else said, I did use an outside caul that pressed the rings down first.

But — and I mean but, not having anything to do with Hesh’s, reportedly hairy butt of another thread — the guitar is only 3 months old and is only a sample of 1 so take this with a grain of salt. I just wanted to point out that this technique, including HHG, is not too difficult for a beginner.


Sent from my iPhone using Tapatalk

We use this sort of clamp in a very, very limited set of circumstances, due both to the amount of time to close the joint and the lack of uniformity in glue line clamping pressure (something known as 'St. Venant's Principle, according to the engineers here). Even with a relatively thick caul inside the body, the bridge wings will essentially be unclamped without supplemental clamping ...which the lack of provisions for accomplishing is what drove the use of the screw-down clamp in lieu of a more reliable solution.

With Titebond's tendency to creep in both cold and hot conditions, hide's lack of creep and ease of repairability seems worth the bother on bridges - even for those that use aliphatic resin or polyvinyl acetate adhesives elsewhere. One lesson early on in this shop was using a warmed bridge to remelt hide glue which had cooled on the bridge patch prior to closing the joint - with a 150 degree F bridge, open time is about 5-6 minutes with 315g and well over ten minutes with 192 glue.

One way to get a feel for this is to glue a heated bridge-sized piece of scrap hardwood to a plywood cutoff (at room temperature) using hot hide glue. Allow the application of glue to the plywood to gel, then apply glue to the heated bridge stand-in, set in place, watch for the liquid glue to come squeezing out of the joint, then clamp. (we use 4-5 clamps). The heat bleeding out of the faux bridge will remelt all of the glue, and the time required for squeeze-out to gel will be extended. Once the test joint is at strength (6 hours for 315g; 24 hours for 192g), use a hammer to shear the joint - a well made joint will see failure in the plywood.

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

I have done a few the way you have mentioned. It seems to work well with supplemental clamping on the bridge wings. It also makes things easier when it comes to stopping titebond glued parts from skating around.

But as was mentioned - you need a good way to drill at least 2 holes through the bridge and top before it's glued.

I've been using 3/16th inch bolts for 20+ years. Now that I use mostly HHG though it's not fast enough to get inside and tighten up the wing nuts. So I still use the bolts because they pin the location good but then I just use 3 clamps. Bolts work great when using Titebond or Fish glue though.

A very clever jig I saw once was using the bolts through a top caul, if you will, basically a 1in X 7in plywood bolted through that sticks straight out and over the bridge wings. The luthier then uses wedges to press into and up against the caul and clamp the wings down.

Wax on the bolts prevent them from getting glued shut.

Since SnowMansnow proposed this idea and bionta has done it this way, should we call it - a biontable snowman clamp? Tis the season

My name on something guitar-related?! And I'm not even dead yet. Woohoo!

Its made out of UHMW so glue doesn't stick, it fits down inside the X brace, the screws are slotted so you can adjust for different pin hole spacings and they are held in place by recessed nuts so once you adjust it you can easily place it inside the guitar. It is deep enough that you won't crush a brace when you put your clamps inside (the bolts apply some clamping pressure but I also use 3 clamps) I made a bunch of them when I worked at an engineering shop, could send the dwg file if anyone is interested

My post above was rather clumsily worded, and improved by others. Thanks, Clay. Rather than change it there, I've clarified the thoughts here:
The 3/16" rod will certainly handle the torque, as illustrated by truss rods. My concern had more to do with turning the wing nuts by hand efficiently and effectively. Smaller rods/bolts have smaller wing nuts, and may benefit from an additional tool to gain a mechanical advantage. Not insurmountable, for sure.
Regarding the glue getting into the threads, I recognize that wax will prevent that, but I'd want to make sure the wood couldn't absorb any wax/non-stick substance, and compromise a critical glue joint.

Mr. De Rocher's photo of the screw-down wing style of bridge clamp highlights one of the problem areas for clamps such as the older Stewart MacDonald design and the one shown: if used as intended, the clamps do not apply any counter-pressure on the bridge plate caul, reducing glue line pressure across the wing area and risking a top crack or excessive top deformation where bridge wings are relatively flexible and the clamp is over-tightened. Clamping the outer screws after an initial light tensioning can address this shortcoming, and provide what - in effect - is 4 to 5 'independent' clamping locations (where applied pressure is not a function of that applied by clamps located closer to the center line). If I recall, several of the repair people here showed their approaches to the job in an older thread a year or so back.

One other thing to consider is the roll of thicker cauls and pressure pads on the bottom of the bridge and on the top of the wings. Force from a clamp propagates through a material in what is roughly a 45 degree cone from point of application, so thicker cauls - a 3/4" bridge plate caul and wing cauls - make for more even glue line pressure. Titebond and other aliphatic resin and polyvinyl acetate glues benefit most from thinner glue lines when considering both cold and hot creep, and higher, more consistent clamping pressure affords thinner, more creep-resistant glue lines - especially for highly stressed joints such as the bridge/top joint.

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

On the UHMW caul in my pictures, the head of the 10-24 bolts stand proud of the inside of the caul with a flat washer under them. Yes, they do get glued into the pin hole but it is a simple matter to reach inside with a 3/8 box end wrench and screw them out (the nut of the face side of the caul is captured by the slot). After a couple of uses I have to replace the bolts because they do get some glue in the threads - no big deal. Glue will also squeeze into the open pin holes - they need to be drilled and reamed but the nice thing is that the caul does not get glued to the guitar.

I had to do that too - reach inside and back out the bolts. It was tedious because they were phillips head machine screws and I had to use a small, offset screwdriver, which was a pain but not a major problem.

My outside caul provided the only pressure on the wings by having little pads of wood in the corners that stood proud of the main body of the caul. I had no caul under the wings on the inside. Seems that the consensus here is that that may not provide enough clamping pressure on the wings. In the future I'll try to make a larger, and thicker inside caul that extends under the wings with grooves cut to bridge over the X-brace.

Oh - almost forgot. I did not have any open pin holes. I just drilled the 2 outer ones before gluing. After the glue dried I made another simple, bridge pad shaped caul out of a piece of scrap, bolted it inside the guitar through the same 2 holes and then drilled the rest of them.

Now, if I'd just been a teeny bit more precise marking the pin hole locations it would have been perfect. I angled the string slot on the A string a wee bit to correct the spacing and so far nobody who's played it has noticed, or they've been too polite to mention it. I think I need to make a drilling template.