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I made a "universal caul" out of thin wood strips which works OK but I've seen others that use a metal loop which seems like a great idea and might conform better to a variety of waist/cutaway shapes - can anyone who has gone this route volunteer what kind of metal they used? I was thinking spring steel but I don't know what gauge would be appropriate so it was rigid enough or even if this is the right choice. Thanks.

What I did was use a 2x2 piece of oak stock and marked the radius on each end of the board. Then used the belt sander to sand the contour onto one side of the board. On the other side (the flat side) I put threaded inserts. Then I drilled two holes on the top plate that was originally holding together the thin wood strips for the “universal caul”. That makes it easier to swap out for other shapes. I’ve noticed the waist bends turn out much better because the caul fits the waist of the body mold exactly.

Don’t forget to glue a couple small wings to the sides to keep the caul aligned in the registration channel.

I saw someone here that did this, which is where I stole it from.

Hope that helps.

Brad


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I do something entirely different. Instead of making a "universal" caul I make a different one for each size and shaped guitar that I build. Since I am going to make an external mold for it anyway, when I cut out MDF or plywood for the mold, I keep the "innies" to be my bending form. For example, here is a Weissenborn in its mold



and the bending caul



I also use the caul to bend all my wood bindings



As far as the metal slats, they are just two pieces of spring stainless steel.

Here is the same idea, completely different guitar (ES-175 style). Bolt four pieces of MDF together with flathead bolts and cut them out on the band saw. Sand the thickness of the sides off of one or the other



Make a body mold with a little gizmo for the Florentine cutaway



Make a caul for the bender



When I put them away I just put the caul back inside the mold so they'll be together for the next time

I was actually talking about the caul/ram at the end of the press screw, not the form itself but it turns out that your bender has exactly what I was referring to. Is there something solid inside the metal loop that you change out for different forms or is it stiff enough to conform without collapsing? I'm trying to figure out what the correct material/gauge would be.


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My bender is a commercial Fox style, the waist caul was on it when I bought it. Frankly I've never paid much attention to it - it is wood with the sheet metal covering. I have never changed it and I bend everything from parlors to fairly large guitars - it seems that once I have set the two holders for the upper and lower bout that simply screwing it down brings the side totally into the waist. It most definitely does not conform to the curve of the waist. I also haven't paid that much attention to the little metal covering - it was on when I bought it and its worked fine ever since. I would assume that it is not spring steel, probably just some 22 gauge stainless.

Remember that thing is pushing down on a fairly thick sandwich - the side has kraft paper on both sides, then the stainless slats top and bottom, then on top the heating blanket.

I'll add that I do not have the Venetian cutaway bending option for my Fox bender - I simply don't do cuts on acoustics (the 175 was a special case and the cut was done on a hot pipe).

I would be happy to take a closer look at the waist caul and take some pictures of it, but as I've said, it just works fine so I've never given it much thought.

I have a Blues creek bender and it has .022 ss. It used to have a 1.5" wooden dowel inside but I took it out. Seems to conform to the waist a little better. Still plenty rigid.

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Pat

I made a Fox bender and tried a wooden caul shaped by eye. It caused problems so I made one with out of galvanized roofing flashing, loop, as shown somewhere. Same material I used for metal slats. Works much better.

I am building a bender from plans that seem to have been copied from a Blues Creek Bender. It has an 1 1/2" dowel inside the ss cover. Upon looking at it, it doesn't look like it would conform to all waists. You removed the dowel. Is the ss sufficient to bend the waist? I realize this is an old post I am on. Have you changed anything since then?

I was thinking a bundle of metal rods might substitute for the dowel and spread out to support the waist. Any thoughts?

thanks, I appreciate any help you can be

fred

wondering if you could take those pictures of the caul and post them??

fred

Yes the .022 stainless is sufficient. It doesn't really conform to the waist. It just flexes slightly more than with the rigid dowel.

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Pat

My bender has a piece of 2 1/4" diameter pipe covered with stainless. I bend everything from soprano ukes to large guitars with the same caul. It's true that an individual shaped caul for each size would be ideal, but it only takes a couple of minutes on a hot pipe to adjust the waist and it's a subtle adjustment. No chance of breakage or scorching. You can see it here http://www.pegasusguitars.com/how-i-ben ... sides.html

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When I first built a Fox type side bending machine I used the original plans from LMI which had an adjustable waist caul comprised of multiple wooden slats which could be adjusted to fit different waist shapes. The problem in using it was that the individual slats with rounded ends made little ripples/creases in the side wood even through the blanket and steel backing strip. Ruined an african blackwood side and decided to move over to a solid caul which matched the waist shape and have never looked back. It's a pain making a bending caul for each body shape but worth it in my opinion

I also have a caul for each body shape. Works for me.

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We have used all three types of waist cauls for blanket benders in the shop - adjustable (per the LMII plan), universal (the Blues Creek bender sheet metal solution), and dedicated. The dedicated caul is superior for our purposes - we make them up from 2x big box poplar or other medium density hardwood. As Mr. Thompson mentioned, it's adds an additional step to the prep process (fabrication of body and neck template, outside mold, bending form(s), and waist caul), but avoids any issue with fit at the waist during bending. For a one-off shape, it still seems a much better idea to bend on the pipe and avoid the extra work and need to store or dispose of unnecessary jigs and fixtures.

The same offset layout technique using nylon spacers I mentioned in a previous post on molds and bending forms is employed for the waist caul, with some block plane work finishing things up to the layout line. We mark directly to cardstock (a re-purposed file folder works), cut to the line with a sharp pair of shears, and mark the blank, then mill to the line. For shops with more than one bender (we run two), making up a second caul gets that second side bent and trims a half day off the timeline when working with woods like mahogany that benefit from an overnight rest in the bender.

We also bend our Florentine cutaway sections in the blanket bender, with the show face upwards in the bender and the usual bending package of slats, foil, paper, stock, and blanket. The caul and form look a bit odd, but it works beautifully.

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