Need Help!- Inserts Breaking every part?

[stuby]

Im not sure if this is the right thread for this, so forgive me if Im wrong. I am making a long roller on my Leadwell LTC-15 2 axis lathe, with a fanuc-ot controller. They are 14 inches long, and .750 in diameter. My job is to turn the stock size down to .630 every quarter inch throught the whole length. Pretty simple, right? Well I ran the program fine for about 4 days, maybe 5. I got about 65 parts completed, I need to make 80. well anyway, I came in one morning, and changed the insert since it was worn very badly from the day before. Up to this point I had only used 3 insert sides total. I replaced the insert with the exact same one, same hardness and everything. I ran the part, and the insert was absolutely destroyed. Naturally, I thought I mave not heave seated it corrrectly, so I replaced it, and triple checked to make sure it was seated correctly. I ran a new part, and the insert broke yet again. Needless to say, I checked all of my tool holduing, and the workholding, all of it is nice and straight, chip free, and tight. I have since then broken down the setup, and re-did it, and still the same problem. Ive gone through 5 insert sides already, and not a single good part. I hate to struggle to complete the last 10% of a job. Im at a real loss here. any help would be appreciated. Thanks.

[big_mak]

Is the new material fomr a different lot? Nothing's been changed in the program?? Someitmes weird things happen @ night!

[DareBee]

Yep, my vote is for wrong part material

[little bubba]

We have a mill with a Fanuc controller on it. It was chewing away on some 13-8, doing pretty good, the tools made it through the 2/3 of the job, and then they just started blowing up, couldn't even get a part completed.

Turns out the tach on the spindle motor was all gunked up so the spindle was turning twice the RPMs it should have been(the meter didn't show this). A 3500rpm machine was doing over 6000. Checked with an external tachometer.

Just something to check.