Inventor General Discussion

## Inventor General Discussion

*Expert Elite*
Posts: 4,298
Registered: ‎04-27-2005
Message 1 of 2 (2,557 Views)

# NPT taper angle in Thread.xls

2557 Views, 1 Replies
08-04-2008 02:30 PM
I noticed in the Thread.xls that the taper angle for a NPT thread is listed as 3.5798°. My handbook says that the taper for American National Standard Taper threads is 3/4in per foot. This calculates to 3.576334° for a difference of only .003466°.

What is in the chart is close enough for me, but I was wondering why the wrong value is in the chart? All the other values for the other columns are exactly like the Machinery's Handbook except for this.

Am I missing something?

Thanks
*udaya \(autodesk\)
Message 2 of 2 (2,557 Views)

# Re: NPT taper angle in Thread.xls

08-04-2008 11:08 PM in reply to: karthur1
3.5798 is the included angle:

3.5798 = 2 * atan( 3/4 * 1/2 / 12 )

The taper is expressed as the change in diameter along the axis.

wrote in message news:5998120@discussion.autodesk.com...
I noticed in the Thread.xls that the taper angle for a NPT thread is listed
as 3.5798°. My handbook says that the taper for American National Standard
Taper threads is 3/4in per foot. This calculates to 3.576334° for a
difference of only .003466°.

What is in the chart is close enough for me, but I was wondering why the
wrong value is in the chart? All the other values for the other columns are
exactly like the Machinery's Handbook except for this.

Am I missing something?

Thanks
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