"Doug Miller" wrote
In article , "Stephen B." wrote:
"Tim Wescott" wrote
On Wed, 27 Jul 2011 21:20:13 +0000, etpm wrote:

The standard taper 3/4 inch per foot is listed in Machinery's
Handbook
as 3, 34, 47.

[...]
It is a question of significant digits.

No, it's not. It's an outright error in the book.

0.75 in/ft calculated to 3 significant digits

Where did you get "3 significant digits" from? 0.75 has only two. If
you're
going to cast this as a significant-digits issue, you need to use
3.6 instead
of 3.58 -- and that gives an even worse answer.

is 3.58 which comes out
to exactly 3 deg 34 min 48 seconds.

Which is *not* the value given in the book.

the math you are calculating is the equivalent to 0.750000000 in/ft
a
far more precise taper.

The value of 3/4 *is* 0.75000000.... and the book is still wrong.

Do you grind and polish your 3/4 inch spacers to that precision?

If you want perfect do not do any math and keep it in a taper
designation ANYTHING else is an approximation.