Thread cutting Ikegai lathe

[hammer28]

Hey I operate an Ikegai fanuc 6t at work and I'm having problems when i'm doing external thread cutting. For some reason its not running over the exact same spot when it takes the first 1 or 2 cuts. This results in a rough finish thats not up to standard.
Ive tried running a few different programs but still get the same problem.
I had a small crash the day before but it was running fine for 6 hours before I had the problem. Maybe something has come loose as a result of the crash?
Has anyone had the same problem? Can anyone help me out??

[hitachibos]

it could be a few things First mark your material to a chuck jaw or a letter on the collett. Make sure the material is not slipping. second might be spindle belts slipping your not telling me the size of part or material but too much tool load could slip the belts.
Third i believe this machine has a taco-generator for spindle feed back thias would be a smaller belt coming off the spindle pullys going to what looks like a small motor near the spindle. check for belt slippage there. also this tac can be cleaned the brushes get dirty. you should be able to tell by watching the RPM display on the screen if you tell it 500 RPM and the screen says 515 thats ok as long as it does not change from 510-520 if your rpm flutters too much your tac is dirty. however from you saying it is only the first or second pass that misses then i would look at a slipping part or belt.

Good Luck

[hammer28]

Hey thanks a lot for the prompt reply. The maintenance guy at work solved the problem while I was away. He said a couple of screws at the back of the turret came loose so he tightened them up and now its cutting threads perfect now. He didn't really elaborate too much about it or show specifically which screws they were (I guess he doesn't want me to do his job!). But thanks for the knowledge about the taco, brushes and belt slippage I'm sure it will come handy in the future. I'm a 2nd year fitting and machining apprentice so every bit of knowledge is great. cheers