"Ed Huntress" wrote in message
...

"Steve Walker" wrote in message
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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.