This page has information and a download link for a single point threading pass calculator.
License: You may freely copy this program and give copies to others. You may not sell it, nor include it with other products for sale, without written permission. The user is liable for proper application of the information generated by this program. We warrant it in the amount of purchase price only.
We took a spread sheet written to program G32/33 threading passes on the old
Fanuc 5T ( Pratt & Whitney Turnmate- still runs). ( I also happen to know a
couple of guys that need to make a manual thread or 3 from time to time.)
The spread sheet was 14K bytes & required Excel to run.
Instructions:
The passes are based solely on a calculated cross-sectional area of material cut per pass. If the total 60 degree triangle cross section of the thread is 1 square inch, and you want 8 passes, each pass will remove .125 square inch. This is the algorithm that Fanuc documents for the G76 cycle on the 6T control.
The radius adjustment is to allow for tools set at the tip and is not deducted from the area before the calculation.
The Ratio value allows the user to specify a reduced depth of cut for the last cut. The ratio is the amount of the average, cross-sectional area that will be cut by the last pass. The material that would have been cut, if the ratio had remained 1.0, is divided evenly between the preceding passes. The Ratio value can be any decimal less than 1.0
For ID's do the following: Calculate for OD, then enter the X value for the last pass as a negative number in the major diameter. The values shown should make a pretty good ID thread, but you may have to adjust a little to get the exact pitch size. Example: 1/4-20 Major Diameter = .2500, last X value on a 5 pass is .1694 Enter -.1694 into Major Diameter, resulting passes are the values for ID as minus values.
This comes in at about 21K (it's not a zip file, it's ready to rock &
roll), doesn't need to be installed, and you can even run it remotely across a
network! Of course I recommend that you always run a virus scanner on a
foreign .exe file. Play with it, test it, let us know if it works for
you . 
Download here
2/15/00 increased number of passes to 20, corrected first compound & Z values, added plc.txt output.
2/19/00 corrected data overprinting, revised adjustment for radius (x2), TPI now calculates thread depth immediately upon input.
