IMO you always get some set.
I think most of the replies should be preceeded by the word "Excessive" as in 'excessive set can be cause by......'
If a finished bow has 1" of reflex, it probably started with 2".
Everything takes set.
The valve springs in you car will take set!
There is a difference between the cells of the belly distorting and compressing slightly, and getting them getting crushed into mush.
IMO, if a bow has no set, it could probably be working just a little harder!
The comments about poor tillering are somewhat missleading, If it's taken a small amount of set evenly along the limbs, I don't see how it can be considered to be poorly tillered.
Even the 'no set' tillering method relies (I believe) on you spotting when it's just begining to take the slightest amount of set.
Trying for absolutely 'no set' is about as feasible as my 'wait til it breaks and go back a bit' method
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Del