The standard taper 3/4 inch per foot is listed in Machinery's Handbook
as 3, 34, 47. When I calculate it I get 3,34,34. I get this answer
using my TI calculator and my computer. Looking on the web I find the
3,34,47 answer. It's the angle I've always used. So how come I get
something different? On my TI-30X calculator I divide .75 by 12 which
equals .0625. This is the tangent. I then use the inverse tangent
function to get the answer: 3.576334375. Then I use the DDDMS
function which returns the answer: 3,34,34 80. So what's going
on??????
Thanks,
Confused machinist Eric

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. When I calculate it I get 3,34,34. I get this answer using
my TI calculator and my computer. Looking on the web I find the 3,34,47
answer. It's the angle I've always used. So how come I get something
different? On my TI-30X calculator I divide .75 by 12 which equals
.0625. This is the tangent. I then use the inverse tangent function to
get the answer: 3.576334375. Then I use the DDDMS function which
returns the answer: 3,34,34 80. So what's going on??????
Thanks,
Confused machinist Eric

A long-ago typo that never got corrected? Was the thing on the web a
table? Maybe they cribbed it out of Machinery's, complete with typo?

I get your answer, by the way.

--
www.wescottdesign.com

"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. When I calculate it I get 3,34,34. I get this answer
using
my TI calculator and my computer. Looking on the web I find the
3,34,47
answer. It's the angle I've always used. So how come I get
something
different? On my TI-30X calculator I divide .75 by 12 which equals
.0625. This is the tangent. I then use the inverse tangent function
to
get the answer: 3.576334375. Then I use the DDDMS function which
returns the answer: 3,34,34 80. So what's going on??????
Thanks,
Confused machinist Eric

A long-ago typo that never got corrected? Was the thing on the web
a
table? Maybe they cribbed it out of Machinery's, complete with
typo?

I get your answer, by the way.


It is a question of significant digits.

0.75 in/ft calculated to 3 significant digits is 3.58 which comes out
to exactly 3 deg 34 min 48 seconds.

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


--
Stephen B.

NOT the Steve B. that posts here regularly

wrote in message
...
The standard taper 3/4 inch per foot is listed in Machinery's Handbook
as 3, 34, 47. When I calculate it I get 3,34,34. I get this answer
using my TI calculator and my computer. Looking on the web I find the
3,34,47 answer. It's the angle I've always used. So how come I get
something different? On my TI-30X calculator I divide .75 by 12 which
equals .0625. This is the tangent. I then use the inverse tangent
function to get the answer: 3.576334375. Then I use the DDDMS
function which returns the answer: 3,34,34 80. So what's going
on??????
Thanks,
Confused machinist Eric

Sorry if this adds to the confusion, but my _American Machinist's Handbook_
(1940 edition) says 3 deg., 34 min., 44 sec. for the included angle at 3/4
in. per foot.

My HP 15C gives me 3,34,34.8.

--
Ed Huntress

On Wed, 27 Jul 2011 18:58:55 -0400, "Ed Huntress"
wrote:


wrote in message
.. .
The standard taper 3/4 inch per foot is listed in Machinery's Handbook
as 3, 34, 47. When I calculate it I get 3,34,34. I get this answer
using my TI calculator and my computer. Looking on the web I find the
3,34,47 answer. It's the angle I've always used. So how come I get
something different? On my TI-30X calculator I divide .75 by 12 which
equals .0625. This is the tangent. I then use the inverse tangent
function to get the answer: 3.576334375. Then I use the DDDMS
function which returns the answer: 3,34,34 80. So what's going
on??????
Thanks,
Confused machinist Eric

Sorry if this adds to the confusion, but my _American Machinist's Handbook_
(1940 edition) says 3 deg., 34 min., 44 sec. for the included angle at 3/4
in. per foot.

My HP 15C gives me 3,34,34.8.
So your book is also wrong. At least I'm not so confused now.
Eric

On Wed, 27 Jul 2011 18:46:58 -0400, "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. When I calculate it I get 3,34,34. I get this answer
using
my TI calculator and my computer. Looking on the web I find the
3,34,47
answer. It's the angle I've always used. So how come I get
something
different? On my TI-30X calculator I divide .75 by 12 which equals
.0625. This is the tangent. I then use the inverse tangent function
to
get the answer: 3.576334375. Then I use the DDDMS function which
returns the answer: 3,34,34 80. So what's going on??????
Thanks,
Confused machinist Eric

A long-ago typo that never got corrected? Was the thing on the web
a
table? Maybe they cribbed it out of Machinery's, complete with
typo?

I get your answer, by the way.


It is a question of significant digits.

0.75 in/ft calculated to 3 significant digits is 3.58 which comes out
to exactly 3 deg 34 min 48 seconds.

the math you are calculating is the equivalent to 0.750000000 in/ft a
far more precise taper.
Thanks Steve and Tim for your replies. It seems that the table on the
web for prop shafts AND Machinery's Handbook are wrong. Kinda destroys
my faith in Machinery's Handbook. It's the first mistake I've ever
found in it. Maybe I should write them a letter.
Eric

wrote in message
...
On Wed, 27 Jul 2011 18:58:55 -0400, "Ed Huntress"
wrote:


wrote in message
. ..
The standard taper 3/4 inch per foot is listed in Machinery's Handbook
as 3, 34, 47. When I calculate it I get 3,34,34. I get this answer
using my TI calculator and my computer. Looking on the web I find the
3,34,47 answer. It's the angle I've always used. So how come I get
something different? On my TI-30X calculator I divide .75 by 12 which
equals .0625. This is the tangent. I then use the inverse tangent
function to get the answer: 3.576334375. Then I use the DDDMS
function which returns the answer: 3,34,34 80. So what's going
on??????
Thanks,
Confused machinist Eric

Sorry if this adds to the confusion, but my _American Machinist's
Handbook_
(1940 edition) says 3 deg., 34 min., 44 sec. for the included angle at 3/4
in. per foot.

My HP 15C gives me 3,34,34.8.
So your book is also wrong. At least I'm not so confused now.
Eric

I think Steve is right, in that small roundings at different points in the
calculation give you very different DMS values. Using a scientific
calculator probably gives us much more accurate results than what they did
to produce the original values in those handbooks.

My 26th Edition of _Machinery's Handbook_ gives the same 3,34,47 you got
from your original sources, BTW.

--
Ed Huntress

In article , wrote:
The standard taper 3/4 inch per foot is listed in Machinery's Handbook
as 3, 34, 47. When I calculate it I get 3,34,34. I get this answer
using my TI calculator and my computer. Looking on the web I find the
3,34,47 answer. It's the angle I've always used. So how come I get
something different? On my TI-30X calculator I divide .75 by 12 which
equals .0625. This is the tangent. I then use the inverse tangent
function to get the answer: 3.576334375. Then I use the DDDMS
function which returns the answer: 3,34,34 80. So what's going
on??????

Book's wrong. Calculator's right.

You can verify this yourself:
3.576334375 degrees = 3 deg 0.576334375*60 min
= 3 deg 34.5800625 min
= 3 deg 34 min 0.5800625*60 sec
= 3 deg 34 min 34.8 sec

wrote in message
On Wed, 27 Jul 2011 18:46:58 -0400, "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. When I calculate it I get 3,34,34. I get this
answer
using
my TI calculator and my computer. Looking on the web I find the
3,34,47
answer. It's the angle I've always used. So how come I get
something
different? On my TI-30X calculator I divide .75 by 12 which
equals
.0625. This is the tangent. I then use the inverse tangent
function
to
get the answer: 3.576334375. Then I use the DDDMS function which
returns the answer: 3,34,34 80. So what's going on??????
Thanks,
Confused machinist Eric

A long-ago typo that never got corrected? Was the thing on the
web
a
table? Maybe they cribbed it out of Machinery's, complete with
typo?

I get your answer, by the way.


It is a question of significant digits.

0.75 in/ft calculated to 3 significant digits is 3.58 which comes
out
to exactly 3 deg 34 min 48 seconds.

the math you are calculating is the equivalent to 0.750000000 in/ft
a
far more precise taper.
Thanks Steve and Tim for your replies. It seems that the table on
the
web for prop shafts AND Machinery's Handbook are wrong. Kinda
destroys
my faith in Machinery's Handbook. It's the first mistake I've ever
found in it. Maybe I should write them a letter.
Eric

I would not go so far as to say they are Wrong. It is just less
precise. Calculating the taper from the angles I get using my excel
sheet:

3 deg 34 min 47 sec = 0.750712... In/ft an error of 0.000712...
3 deg 34 min 34 sec = 0.749953... In/ft an error of 0.000046...
3 deg 34 min 35 sec = 0.750011... In/ft an error of 0.000011...

As you can see the it disagrees with your calculations as to the
correct number of seconds is closest.

Remember the problem with IIRC the Pentium processors way back when?
No one was bothered except those that needed extremely high precision
theoretical math.

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.

"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.

On 7/27/2011 17:20, wrote:
The standard taper 3/4 inch per foot is listed in Machinery's Handbook
as 3, 34, 47. When I calculate it I get 3,34,34. I get this answer
using my TI calculator and my computer. Looking on the web I find the
3,34,47 answer. It's the angle I've always used. So how come I get
something different? On my TI-30X calculator I divide .75 by 12 which
equals .0625. This is the tangent. I then use the inverse tangent
function to get the answer: 3.576334375. Then I use the DDDMS
function which returns the answer: 3,34,34 80. So what's going
on??????
Thanks,
Confused machinist Eric


Coming from a gage making person. You are doing the calculation wrong.
3/4 taper per foot builds a triangle with a base of .750 and an altitude
of 12.000 inches. Base divided by altitude is NOT the tangent. Half the
base divided by the altitude is the tangent of the half angle. Inverse
tangent of that is the half angle, then double that to get the full angle.

--
Steve Walker
(remove brain when replying)

"Steve Walker" wrote in message
...
On 7/27/2011 17:20, wrote:
The standard taper 3/4 inch per foot is listed in Machinery's Handbook
as 3, 34, 47. When I calculate it I get 3,34,34. I get this answer
using my TI calculator and my computer. Looking on the web I find the
3,34,47 answer. It's the angle I've always used. So how come I get
something different? On my TI-30X calculator I divide .75 by 12 which
equals .0625. This is the tangent. I then use the inverse tangent
function to get the answer: 3.576334375. Then I use the DDDMS
function which returns the answer: 3,34,34 80. So what's going
on??????
Thanks,
Confused machinist Eric


Coming from a gage making person. You are doing the calculation wrong. 3/4
taper per foot builds a triangle with a base of .750 and an altitude of
12.000 inches. Base divided by altitude is NOT the tangent. Half the base
divided by the altitude is the tangent of the half angle. Inverse tangent
of that is the half angle, then double that to get the full angle.

--
Steve Walker
(remove brain when replying)

Darn, that's right! I knew something seemed too simple.

So now my HP 15C gives me 3,34,47.4.

Machinery's Handbook was right, after all. Thanks, Steve.

--
Ed Huntress

"Ed Huntress" wrote in message
...

"Steve Walker" wrote in message
...
On 7/27/2011 17:20, wrote:
The standard taper 3/4 inch per foot is listed in Machinery's Handbook
as 3, 34, 47. When I calculate it I get 3,34,34. I get this answer
using my TI calculator and my computer. Looking on the web I find the
3,34,47 answer. It's the angle I've always used. So how come I get
something different? On my TI-30X calculator I divide .75 by 12 which
equals .0625. This is the tangent. I then use the inverse tangent
function to get the answer: 3.576334375. Then I use the DDDMS
function which returns the answer: 3,34,34 80. So what's going
on??????
Thanks,
Confused machinist Eric


Coming from a gage making person. You are doing the calculation wrong.
3/4 taper per foot builds a triangle with a base of .750 and an altitude
of 12.000 inches. Base divided by altitude is NOT the tangent. Half the
base divided by the altitude is the tangent of the half angle. Inverse
tangent of that is the half angle, then double that to get the full
angle.

--
Steve Walker
(remove brain when replying)

Darn, that's right! I knew something seemed too simple.

So now my HP 15C gives me 3,34,47.4.

Machinery's Handbook was right, after all. Thanks, Steve.

--
Ed Huntress


Thanks for making the taper spec clear, I have been confused if the angle
was the included or the half.

Do I have it right that the transition from a jamming taper to self
releasing is close to 7 degrees (included) for steel?

John.

Apparently math is not one of Dougy's strengths. He is so intent on jumping
down people's throats he doesn't think before he types, anymore.

Tangent tables and formulae in calculators are seldom more accuracy than 5
places of accuracy, even though displaying 10 places. The errors can seem
way out-to-lunch at times with multiple steps.

-------------

"Stephen B." wrote in message ...
0.75 in/ft calculated to 3 significant digits

--------------------------
"Doug Miller" wrote
Where did you get "3 significant digits" from? 0.75 has only two.

"Machinist60" wrote in message
...


"Ed Huntress" wrote in message
...

"Steve Walker" wrote in message
...
On 7/27/2011 17:20, wrote:
The standard taper 3/4 inch per foot is listed in Machinery's Handbook
as 3, 34, 47. When I calculate it I get 3,34,34. I get this answer
using my TI calculator and my computer. Looking on the web I find the
3,34,47 answer. It's the angle I've always used. So how come I get
something different? On my TI-30X calculator I divide .75 by 12 which
equals .0625. This is the tangent. I then use the inverse tangent
function to get the answer: 3.576334375. Then I use the DDDMS
function which returns the answer: 3,34,34 80. So what's going
on??????
Thanks,
Confused machinist Eric


Coming from a gage making person. You are doing the calculation wrong.
3/4 taper per foot builds a triangle with a base of .750 and an altitude
of 12.000 inches. Base divided by altitude is NOT the tangent. Half the
base divided by the altitude is the tangent of the half angle. Inverse
tangent of that is the half angle, then double that to get the full
angle.

--
Steve Walker
(remove brain when replying)

Darn, that's right! I knew something seemed too simple.

So now my HP 15C gives me 3,34,47.4.

Machinery's Handbook was right, after all. Thanks, Steve.

--
Ed Huntress


Thanks for making the taper spec clear, I have been confused if the angle
was the included or the half.

Do I have it right that the transition from a jamming taper to self
releasing is close to 7 degrees (included) for steel?

Uh, I hope you're not asking me, and I further hope that someone knows the
answer. That's not something I've done.

--
Ed Huntress


John.

On Wed, 27 Jul 2011 18:46:58 -0400, 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. When I calculate it I get 3,34,34. I get this answer
using
my TI calculator and my computer. Looking on the web I find the
3,34,47
answer. It's the angle I've always used. So how come I get something
different? On my TI-30X calculator I divide .75 by 12 which equals
.0625. This is the tangent. I then use the inverse tangent function to
get the answer: 3.576334375. Then I use the DDDMS function which
returns the answer: 3,34,34 80. So what's going on?????? Thanks,
Confused machinist Eric

A long-ago typo that never got corrected? Was the thing on the web a
table? Maybe they cribbed it out of Machinery's, complete with typo?

I get your answer, by the way.


It is a question of significant digits.

0.75 in/ft calculated to 3 significant digits is 3.58 which comes out to
exactly 3 deg 34 min 48 seconds.

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

Then the handbook is providing too many significant digits in the answer!



--
www.wescottdesign.com

On Wed, 27 Jul 2011 21:16:46 -0400, Steve Walker
wrote:

On 7/27/2011 17:20, wrote:
The standard taper 3/4 inch per foot is listed in Machinery's Handbook
as 3, 34, 47. When I calculate it I get 3,34,34. I get this answer
using my TI calculator and my computer. Looking on the web I find the
3,34,47 answer. It's the angle I've always used. So how come I get
something different? On my TI-30X calculator I divide .75 by 12 which
equals .0625. This is the tangent. I then use the inverse tangent
function to get the answer: 3.576334375. Then I use the DDDMS
function which returns the answer: 3,34,34 80. So what's going
on??????
Thanks,
Confused machinist Eric


Coming from a gage making person. You are doing the calculation wrong.
3/4 taper per foot builds a triangle with a base of .750 and an altitude
of 12.000 inches. Base divided by altitude is NOT the tangent. Half the
base divided by the altitude is the tangent of the half angle. Inverse
tangent of that is the half angle, then double that to get the full angle.

Which gives the correct answer (one in the book). I thought there was
something wrong, but too lazy and foggy at 6am before my first coffee.
Thanks, Steve.

Pete Keillor

On Wed, 27 Jul 2011 22:14:46 -0400, Machinist60 wrote:

Do I have it right that the transition from a jamming taper to self
releasing is close to 7 degrees (included) for steel?


Jamming needs the tangent of the half-angle to be less than the
coefficient of friction; steel-steel is about .15, giving about 10
degrees.

On Wed, 27 Jul 2011 22:10:31 -0400, "Ed Huntress"
wrote:


"Steve Walker" wrote in message
m...
On 7/27/2011 17:20, wrote:
The standard taper 3/4 inch per foot is listed in Machinery's Handbook
as 3, 34, 47. When I calculate it I get 3,34,34. I get this answer
using my TI calculator and my computer. Looking on the web I find the
3,34,47 answer. It's the angle I've always used. So how come I get
something different? On my TI-30X calculator I divide .75 by 12 which
equals .0625. This is the tangent. I then use the inverse tangent
function to get the answer: 3.576334375. Then I use the DDDMS
function which returns the answer: 3,34,34 80. So what's going
on??????
Thanks,
Confused machinist Eric


Coming from a gage making person. You are doing the calculation wrong. 3/4
taper per foot builds a triangle with a base of .750 and an altitude of
12.000 inches. Base divided by altitude is NOT the tangent. Half the base
divided by the altitude is the tangent of the half angle. Inverse tangent
of that is the half angle, then double that to get the full angle.

--
Steve Walker
(remove brain when replying)

Darn, that's right! I knew something seemed too simple.

So now my HP 15C gives me 3,34,47.4.

Machinery's Handbook was right, after all. Thanks, Steve.
OK, now I see it. I took a short cut that was wrong. I really have two
angles with the tangent .03125. These angles added together do indeed
equal 3,34 47. Thanks Steve . Normally I work with the centerline but
yesterday I was lazy and not thinking. I hate it when I'm wrong about
stuff like this. But it's great when someone points it out to me and I
can correct my thinking.
Eric

"xpzzzz" wrote in message ...
On Wed, 27 Jul 2011 22:14:46 -0400, Machinist60 wrote:

Do I have it right that the transition from a jamming taper to self
releasing is close to 7 degrees (included) for steel?


Jamming needs the tangent of the half-angle to be less than the
coefficient of friction; steel-steel is about .15, giving about 10
degrees.

Thanks, you confirmed I had it close.

John.

"Tim Wescott" wrote
On Wed, 27 Jul 2011 18:46:58 -0400, 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. When I calculate it I get 3,34,34. I get this
answer
using
my TI calculator and my computer. Looking on the web I find the
3,34,47
answer. It's the angle I've always used. So how come I get
something
different? On my TI-30X calculator I divide .75 by 12 which
equals
.0625. This is the tangent. I then use the inverse tangent
function to
get the answer: 3.576334375. Then I use the DDDMS function which
returns the answer: 3,34,34 80. So what's going on?????? Thanks,
Confused machinist Eric

A long-ago typo that never got corrected? Was the thing on the
web a
table? Maybe they cribbed it out of Machinery's, complete with
typo?

I get your answer, by the way.


It is a question of significant digits.

0.75 in/ft calculated to 3 significant digits is 3.58 which comes
out to
exactly 3 deg 34 min 48 seconds.

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

Then the handbook is providing too many significant digits in the
answer!


True, but I tend to believe Steve Walker's answer.

There is allot about machining that I do not know. Such as how to use
the angle to machine the taper, let alone measure it half way
accurately.