View Full Version : How to program 1/8-27NPT on old FANUC 18T Screw Machine

04-13-2010, 01:30 AM

Would anyone know how to program external 1/8-27NPT thread on a FANUC 18T? What cycle to use and what format? I don't have a book available. Could anyone perhaps direct me to a source of some understandable instructions so I can read up?


04-13-2010, 09:03 PM
G76 cycle if your machine has it, is best as it offers the most control.

Do you have any manuals for the control to refer to? Some (rarely) are setup for single-line G76, most use the two-line format. I don't have the dimensions for a 1/8-27 NPT with me so I can't give specifics, but the format would be something like this:


I'd have to find my notes to give you specifics, but the first line P sets number of "spring passes" at final depth with the first pair of digits, thread end chamfer witht he middle pair, inckuded angle of thread for the 3rd pair. The first Q is the clamp value, meaning the smallest infeed increment. The first R is the finish allowance, meaning how much the final pass before spring passes will be.

In the 2nd G76, the X is the final diameter of the thread root, the Z is the length of thread, the P is the total "per side" height of the thread, the Q is the depth of 1st pass, the R is the the incremental (per side) amount of taper, the F is the lead of the thread.


04-14-2010, 02:29 AM
Thanks for the reply, PixMan.

It would be appreciated if you could occasionally check this thread, as I may need some more assistance. I needed to set up another job since I coulnd't figure out how to program NPT.

Although I could not resist to input the data into the machine. It gave me an alarm, but that's only because I cannot use a decimal point using the formula. I have to program using, for example, " .1"=1000" "
As soon as I converted the numbers, the alarm dissapeared. So my guess would be that your formula should work on this controller. I had no time to play with it, though, so I don't know for sure what problems I'm goign to get into. This is why I would like to appreciate it if you could check this thread incase something comes up.

I feel confident on boring mills and milling machines, but a screw machine with FANUC is definately a challenge.

Once again, thank you very much.