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Hi!

I read here that some of you make their bending forms 0.1 smaller than the actual sides.
Being a little obsessed with accuracy, I'm trying to find the way to offset of that much from my full size template on a router table.
I'can't seem to find the right combination of bushing or bearings producing a 0.1 offset.
Any help welcome!

Thank you.

first off , do you use a building mold ?
2nd when you plan to make a template you need to consider not all wood will bend the same. I bend about 250 sets a year and here is what I can pass on to you.
Spring back will happen so there seldom will be a perfect bend with every wood . I set up my pattern this way
off the center line not the apex of the bout and curve off the full size pattern.

then compensate the bend by about 1/4 in so if the upper bout is say a 10 in radius start the curve at the point and flex if as it travels to the block. the waist just a tad tighter and lower bout , again about 1/4 in radius tighter than the design.

this way the curve apex will match the mold and the spreaders will draw you tight.
https://www.youtube.com/watch?v=QYHPCeVRUA4

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Thank you very much for a clear and concise answer John. I truly appreciate your help as I do enjoy your videos.
PS: Yes outside mold is involved.

Jean-Michel

I have both molds for bending the sides, and outside molds for assembly. The inside molds that I bend with are cut using an 1/8" Whiteside spiral flush cut bit, (part #RFT1600) using the outside mold as the template. My sides, however, are not 1/8" thick, so its a little smaller than the actual dimensions for the side.