Been programing mills for 35 years. Shop I do work for bought a Takisawa ts10 lathe with a 10t control. Owner could not figure out how to use it. Silly me I said I could probably figure it out. After crash course in work shift and tool holders not on center etc I've managed to get a couple of runs of parts off the machine. Next hurdle - how to make a variable pitch thread. The yellow Fanuc operator's manual has to be the most frustrating experience I've encountered in quite awhile. G33 threading cycle has so many options I'm confused. Just need an example to start with. Let's say 1" dia with a thread that goes from 5 per inch to 10 per inch in 3 inches. No taper. Just need a format example and I can probably figure out things from there. Thanks very much. MG in Bend, OR

2. First of all, I'm in Florence, OR and it's 32 degrees here. I'll bet it's a cold one in Bend.

I've never actually cut a variable pitch thread, but I believe the G34 block should have a Z for the destination, an F for initial feed per revolution and a K +/- for the amount to increase or reduce the IPR each revolution.

Maybe there's a math whiz out there that can give you the formula, but I made an Excel spreadsheet to calculate it out.

This is just a guess, but you might give it a try (away from the part):

G00 X0.98 Z0.4 (START POINT)
G34 Z-3.0 K-0.0052 F0.215
G00 X1.1
Z0.4
X0.96
G34 Z-3.0 K-0.0052 F0.215
G00 X1.1
Z0.4
X0.945
G34 Z-3.0 K-0.0052 F0.215
G00 X5. Z5.

I think this will start Z at 0.4 from the part and feed 0.215 the first turn, 0.2098 the 2nd turn, 0.2046 the 3rd turn, etc. until it gets to Z-3.0144 at which time it will have fed 0.1006 on the last turn.

Hope this helps. If you want my spreadsheet, you're welcome to it.

Dave

3. Where does one use a variable pitch thread?

4. Hose fittings and oil industry.

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