Clamping caul for bridge and fingerboard extension

[Albert D]

I'm making progress on my first build and have started putting finish on my neck while I wait for the body lacquer to cure for a couple of weeks. I need to make clamping cauls for the bridge and fingerboard extension. I know it's closing the barn door after the horse got out but I have the plans to help me. What I am wondering is do I make them to span the braces without touching them? That makes sense to me but want to make sure.

Any other suggestions would be much appreciated too. Thank you.

[ChrisN]

For a classical bridge I recently replaced, I used a 1" x 6" x .5" piece of wood that I then laboriously grooved using a rat tail file to clear the braces. At the moment, I don't recall exactly how I did it, but I used strong magnets (round ones from ACE) to hold the wood in place against the braces under the bridge area while I used a pen to scribe where the braces were, removed, filed, replaced, repeat until there was no tension on the braces. It wasn't quick, it wasn't perfect, but it worked for me.

[Howard Klepper]

Originally Posted by Albert D

I'm making progress on my first build and have started putting finish on my neck while I wait for the body lacquer to cure for a couple of weeks. I need to make clamping cauls for the bridge and fingerboard extension. I know it's closing the barn door after the horse got out but I have the plans to help me. What I am wondering is do I make them to span the braces without touching them? That makes sense to me but want to make sure.

Any other suggestions would be much appreciated too. Thank you.

Right, the caul does not put pressure on the braces. Make sure that where the caul contacts the top outside of the X, you add a layer of wood to it that is equal to the thickness of the bridge plate, and match the whole caul to the radius of the top.

Working from the drawing is not much of a handicap, but make sure when you put the caul in that it is located properly and not putting pressure on any braces.

[Albert D]

Thank you both. I tend to over think simple things. I just don't want to hear a big cracking noise when I tighten the clamps.

[ChrisN]

Now that I'm thinking back, I wonder if I didn't initially use the magnets above/below the top (without the caul) to show me where the braces were. The magnets would slide easily (no damage to top) sitting on a piece of waxed paper.

[Albert D]

Originally Posted by ChrisN

Now that I'm thinking back, I wonder if I didn't initially use the magnets above/below the top (without the caul) to show me where the braces were. The magnets would slide easily (no damage to top) sitting on a piece of waxed paper.

Chris, I have the plans and it's built pretty much right to the plans. It's scratch built but from the StewMac herringbone plan. I will have no problem taking dimensions right from it. I'm going to make it a fun project on its own and use my Sherline mill to make both cauls. I need to learn the machine anyway.

[ChrisN]

Originally Posted by Albert D

I will have no problem taking dimensions right from it.

Well, where's the fun in that? You're removing the elements of surprise and despair that are integral to home lutherie.

[Albert D]

Originally Posted by ChrisN

Well, where's the fun in that? You're removing the elements of surprise and despair that are integral to home lutherie.

Yea, I know but I spent years as a draftsman so I have a thing for plans. I have run into a fair number of surprises along the way though. At this point a cracked brace is a surprise I don't need.

[phavriluk]

Seeing as OP is trying to get some value out of his lovely mill, I suggest he fish around and find drawings for a 'bridge setting tool' that clamps a bridge in place from the outside. Perfect mill project, a couple of bucks of hardware and a hunk of aluminum makes a tool that vendors charge thirty bucks for. No drawings are needed, just look at the images of one and put the mill to work.

[Albert D]

Originally Posted by phavriluk

Seeing as OP is trying to get some value out of his lovely mill, I suggest he fish around and find drawings for a 'bridge setting tool' that clamps a bridge in place from the outside. Perfect mill project, a couple of bucks of hardware and a hunk of aluminum makes a tool that vendors charge thirty bucks for. No drawings are needed, just look at the images of one and put the mill to work.

That sounds like another great project. I love figuring out how to set the mill stock up and plan out cuts.

[surveyor]

A while back I bought some stuff called "friendly plastic" in a granule form. You microwave it until its turns to a form like play dough, take it out and form it around your braces and whatever, let it dry and remove, thereby leaving you with a cast of the objects you want to build around. I bought it for making impressions of inlays to use on a pantograph for inlaying fingerboards. Oh, be sure to put a layer of cellophane or something so it won't stick.

[charles Tauber]

While friendly plastic has a variety of interesting uses, there are a bunch of ways that are quicker and easier than using it to determine the placement of internal top braces.

If a top is spruce, placing a strong light inside the guitar and viewing it in a dark room will make the guitar top translucent, from which one can easily see the position of all internal bracing. (George Morris, one of my guitar making teachers, used to make lamps from thin sheets of spruce. Such is the nature of spruce.)

For any thin wooden material, a few pairs of rare Earth magnets can be used to easily determine the placement of internal structural elements. Place one of each pair on the inside abutting braces of interest and the other on the outside.

[dantin]

Never tried this before but Dan Erlewine has a method of using styrofoam blocks.

https://www.youtube.com/watch?v=aWW4aKxfSJw

[Albert D]

Originally Posted by dantin

Never tried this before but Dan Erlewine has a method of using styrofoam blocks.

https://www.youtube.com/watch?v=aWW4aKxfSJw

That's sure interesting. I would think a stiffer backing than his 1/8 hobby ply would be safer due to flexibility. I'll be making my caul's in the next few days. I picked up some oak. I don't have a good source of maple.

[redir]

Originally Posted by dantin

Never tried this before but Dan Erlewine has a method of using styrofoam blocks.

https://www.youtube.com/watch?v=aWW4aKxfSJw

It works brilliantly. Been doing it that way for years. I think I remember it being in an old SM trade secrets section of their catalog probably written by Dan.