maximum thickness of back

[Happy Builder]

i am building a guitar and back seems to be 4mm i dont fell like thinning it ant more -- will it do

what is the maximum thickness allowable for top back and sides

[Pierre-Antoine Roiron]

I only build electric instruments, but when I have to repair backs or sides, I usually use the same thickness ass the rest of the part I'm repairing. And all I've seen is always between 1.5mm and 2.5mm.
I don't see why a 4mm back wouldn't do the job (as long as you make it almost flat)... but it would be somewhat heavy, isn't it? For a top it would be too stiff and for sides maybe a bit difficult to bend.

[Happy Builder]

thanks heavy is not a problem but will there be other problems --- some say back has to reflect others say back has to resonate --- or is it both --- any idea what would be the effect on sound

[Greg Mirken]

4mm is very thick; 2.5 is more like it. The back is part of the sound producing system and a back that heavy isn't going to vibrate much.

[Happy Builder]

when you say that it wont vibrate much will it only reduce volume or any other problems will occur

[FRANK]

thicker braces i believe add more treble. Sound hole makes a difference also ?A thicker back hmm cant answer that try it and tell please

[Frank Ford]

A thinner, more flexible back can add substantially to the bass response and "fullness" of tone. If you doubt that, sit down with a good guitar, and strum some full chords holding the guitar back against your gut, then hold it so you don't touch the back at all.

That said, Martin is always a good standard to examine.

Back thickness of modern D-28 is just under 3 mm, including the finish, or .117"

I just measured a truly great 1937 D-28 that's on my bench right now - its back is 2.5 - 2.6 mm, or very close to 0.100" thick

[Happy Builder]

thanks i think you are right
the gr8 sounding ones should set the standard
i will go with 2.5 mm to 3 mm
rgds