>" can't I measure with fair accuracy..."

when i fixture a frame, (CR content: even tho it's not a 1" top
tube frame...), i cut the tubes to fit the fixture. once the frame
is brazed, i refixture around it and double check against the prescribed
numbers. if any at all, the only changes occur in the front center measure
- it can shrink .5mm, and in the head angle - it can come by by a minute
or three. this is due to heat expansion and contraction. after i refixture
around the finished frame, i record the numbers and write them in the book.
to tell you the truth, i can't remember any client ever addressing these
numbers and saying either 'yea' or 'nea' to what i describe the frame's
numbers to be. if i tell a guy it's a 42cm chainstay and he wants to
measure it, why does it matter if he uses a rule and i use my fixture?
if i measure a 42cm chainstay on a frame and the book says i wrote down
41.75cm, i usually buy myself a pink guitar and listen to adrian balou.
ya' know what? there are no guitars here. why? because i went to high
school and if the discrepency example i cite here were ever a reality,
i would not have finished making the frame. so, when you ask,"...what
can't I measure with fair accuracy to double-check what the builder
promised?" i assume you meant to write, "...why can't i...", you can
measure it. if you're not clear on why a difference may exist, ask the
frame's builder. if he tells you his numbers are the centreline
ones we've discussed, that will explain why they differ from the
ones yielded from the tapemeasure.