Making custom fit internal bridge gluing cauls

Hi all, how do you guys approach making custom bridge gluing cauls  for bridge plates and cauls to go around braces?

How do you trace the pattern to cut?


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I have an assortment of little magnets that i use to find all the braces and such through the top to a piece of paper (be gentle with the pencil). By putting a set of magnets at either end of a given brace you can connect the dots with a ruler and apply the finished pattern to a piece of hardwood or whathaveyou. You could augment this approach with a thickness gauge of some sort for heights of braces etc, but I typically just eyeball the recess i need to create to bridge an obstruction unless I specifically want support on a given area.

Another approach would be to apply some styrofoam insulation to a backer block and clamp that in place, so that the brace pattern will be impressed upon the foam, which can the be cut away using a razor knife (my Olfa is one of my favourite tools). 

Im sure Ive used a few other methods but these two jumped to mind first..

Thanks Andrew.

The styrofoam sounds good to me.

Bright light inside the body under the bridge, tape tracing paper around the bridge, trace out the shadow.

Wow tha must be a hell of a bright light! What wattage are we talking about?

I do it in a dark room with a 100 watt equivalent CFL or LED bulb. A spruce guitar top with a clear finish is very translucent and the braces show up clearly as shadows. Just put the light directly under the area you're tracing. 

Great! Thank you Mark.

Just a quick addition to methods to trace braces which may add to the mix:   I stick a small dot magnet to my finger tip and with a sheet of paper taped to the outside run my finger around the area inside and track it with a similar dot magnet on the outside - crayon the path of the track and you end up with a rough and ready map of where everything is - rudimentary and quick.



I wonder how this would work with a bit of carbon transfer paper taped to the magnet to do it in one motion. 

These are all great tips .. I've used the magnet trick, and also have used aluminum foil and folded it over the brace/s to make a 'pattern' then remove carefully and trace to wood.  I prefer the magnets, though, for optimum accuracy.


Nice one too!


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