I do not place a bridge on the body, because the bridge is to thick at this point in construction, the fingerboard is not attached to the neck when i do this. i put the aluminum bar up against the body of the guitar at the heel block. i have already set the distance of the dial gauge to be at the bridge position. i then zero the dial gauge pointer with the face of the aluminum bar (the part of the bar you would normally take your measurement from). You must take into account the amount of doming of the top if any, to get the amount of fall away at bridge position. Then if i want a bridge of lets say 5/16" thick like mine, you take .3125" - .250" (fingerboard thickness at the center of the crown) = .0625". Then you account for the fall away distance between the bridge position and the dial gauge zero point (or your aluminum bar stock, at this point they are the same). Lets say the fall away is .095". so you add .095" + .0625" = .1575". Next we subtract .1575" from .3125", which gives us the neck angle measurement of .155". Finally if we know our top deflection at bridge point, we can add this number to the total. lets say the top deflection on previous instruments when strung up is .025". so .155" + .025" = .180" This would be the measurement you would dial in with the guitar body in place.
Now if you make the same model many times, just make a .1575" or .158" shim and put in in the bridge position. to set the angle without deflection comp or .180" with. These would not be exact numbers for everone, but for one specific model with specific bridge placement and doming.
Another point to make is that the rotational force on the heel block can be kept to a minimum by adding a fingerboard extension and a foot to the heelblock design, which extends all the way to the UTB and the foot to the backs first brace closest to the heelblock.
This is the top deflection gauge from stewmac, or they are easy to make.
Here is a great article written by Hesh on the forum here on neck angle.http://www.lenaweelu...e30/page30.html
Edited by Rick Dingman, 21 August 2012 - 07:11 AM.