Tapered Thread Milling CNC Code Generator
Version 3.25


  1. Insert the PIPETHRD diskette in the floppy drive of your control
  2. Press F7 for the Utility screen
  3. Press F2 for Update
  4. When the "Installation complete" message appears, press ESC to return to the Utility screen, then press ESC again to return to the main control screen.


From the control's main screen, press F5 for CAM, then press whichever function key is shown for PIPETHRD. This will often be F4, but depends on what other software you have installed on your control.

Special Note for Windows CNC10 Users:


On Windows-based CNC10 controls the F5/CAM menu cannot be extended to include PIPETHRD. Instead, use a desktop shortcut to launch the program. The shortcut should run C:\CNC10\PIPETHRD.EXE, and should specify C:\CNC10\NCFILES as the working directory.

From the control software you can press F10/Shutdown, then F9/Exit to exit CNC10 and show the desktop. Double-click the PipeThrd shortcut to run. When you are done, double-click your CNC10 Mill shortcut to restart the control software.

PIPETHRD will prompt you for the thread milling parameters:

These parameters will default to whatever you entered last time you used PIPETHRD. If you do not need to change a value, just press ENTER to keep the default.

When you have entered all the parameters, press F10. PIPETHRD will write the CNC file, then return to the main control screen.

On DOS-based controls, the new thread milling CNC program is loaded automatically. On Linux-based controls and CNC10 Windows-based controls, The new thread milling CNC program is not loaded automatically. Press F2 for Load, use the arrow keys to highlight the new program's name, and press F10 to accept it.

The resulting CNC program will use cutter radius compensation (G41 or G42). You can, therefore, adjust the fit by changing the tool's diameter offset value in the Offset Library.

If you have problems with cutter compensation, try subtracting the cutter diameter from the thread diameter and using the diameter offset only for wear compensation (i.e. start with 0.0 in the offset, and add or subtract small amounts as needed to fine-tune the cut dimensions).

The header and footer codes (G codes inserted at the beginning and end of the program, respectively) can be customized.

On DOS-based controls, load and edit PIPETHRD.HDR and PIPETHRD.FTR, located in the C:\CNC7 directory.

On Linux-based controls and Windows-based controls, load and edit pipethrd.hdr and pipethrd.ftr, located in the c:\cnc10 directory.

In the header and footer codes, you may include the symbol %T any place you want to insert the Tool Number specified on the PipeThrd screen. All other codes are inserted literally, just as you type them.

Default header codes are:

  M6 T%T
  M3 S800

Default footer codes are:


Surface diameters for NPT threads

Size Pitch Int. Sfc.D Ext. Sfc.D
1/8 .03704 0.3896 0.3475
1/4 .05556 0.5157 0.4533
3/8 .05556 0.6511 0.5880
1/2 .07143 0.8094 0.7275
3/4 .07143 1.0198 0.9367
1 .08696 1.2763 1.1760
1-1/4 .08696 1.6210 1.5195
1-1/2 .08696 1.8600 1.7584
2 .08696 2.3339 2.2314

These are approximate starting values. The surface diameter you need depends on thread mill tip geometry and thread fit requirements. As a rule, you will need to make test cuts in scrap material, starting small and working up, until you obtain the desired fit.


This software and documentation are copyrighted with all rights reserved.

I make no warranty, express or implied, with respect to their quality, performance, or fitness for a particular purpose. They are provided "as is", and you assume all risk associated with their use.

You should use all available means to verify that the job will run safely before you press the CYCLE START button. These include, but are not limited to, the F8/Graph and F6/Edit features of your control.

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Copyright © 1999-2008 Marc Leonard