Using U To Program Taper CNC Lathe

Using U To Program Taper CNC Lathe

Category : Fanuc Turn Haas Turn

I recently wrote an article on the use of incremental U and W on a CNC Lathe for incremental programming.

I must be honest I didn’t have that many creative uses for it.

Anyway when I posted it on Linkedin I did get some interesting replies and comments. I was surprised to see how many people do use incremental U and W.

incremental U


About a year ago I was working at Gardner Aerospace and we were struggling to get rid of a taper on a shaft we were machining.

Not a particularly difficult job other than this pesky taper we kept getting.

It was something like 30mm diameter by about 140mm long. We were making it on a new Haas ST lathe we struggled to hold the size which was about plus or minus .02mm and were getting a taper too.

I noticed that when we programmed a taper it was easy to make a mistake.

incremental U

The above program would take the size .015 less.

incremental U

When it came to changing the taper again the calculation had to be made. I suddenly had a brainwave and realised we could program it in incremental by using a U figure.

incremental U

The great thing about doing this is that you can see exactly what taper you have and it’s really easy to modify. 

The other thing is that the figure is always going to be small so it’s easy to spot mistakes.

I got so excited I even made a video.

Thanks for watching and reading

If you have been affected by any of the issues in this post or need CNC Counselling then contact me.

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