thead cutting issue on a cnc lathe

The Right Choice · Feb 22, 2018

I have a small cnc gang lathe with a fagor 8025 controller. When I cut threads with g86, it looks like the backside of the thread is tearing and rough. It was working okay and seems to have started cutting rough. Using Nickole mini systems bar, new carbide. tool block is zeroed, no crashes.
It doesn't matter how shallow or deep the thread cuts, it always looks rough on the backside.

sinha · Feb 23, 2018

Check tool wear.
Try smaller DOC.

FredC · Feb 23, 2018

Not familiar with the fagor controller, does the G86 give you an angled infeed? The tearing looks to be caused by chip thickness. Trying different infeed angles 29.5 to 27 could help if that is the issue.

alphonso · Feb 23, 2018

What is your "A" value? Try 29 or -29 (this will give you alternating flank cuts. Works really great on 4.5 X 6 in 17.4ph!)

The Right Choice · Feb 23, 2018

I'm not sure on my "A" Value, the tool bit is 60degrees included angle. For Fagor 8025, using G86, I believe that would fit into P12=60? I'm pretty new to cnc machining only a year or so, learning it as I go is a steep hill.
I'll try 29 for P12 value.

The Right Choice · Feb 23, 2018

Okay, I feel pretty dumb. I change the P12 value to 29 and it works great. I thought the canned cycle figure the correct angle if I input the included angle of the tool bit.
Thanks for the help.

Bobw · Feb 23, 2018

The Right Choice said:
I'm pretty new to cnc machining only a year or so, learning it as I go is a steep hill.

I cut my teeth on an 8025 also.. It is not an easy control to deal with, it is not an
easy one to program... It is pissy, the manuals suck, the error codes are never actually
what they are...

Keep good notes.. I used to have a nice cheat sheet, wish I had made copies.. Notes on
what the error codes actually meant.. How the canned cycles actually work... That kind
of thing...

If you can wrap your head around that P0, P1, Fagor crap... Any other control is going
to be a piece of cake.

The Right Choice · Feb 23, 2018

Hah, I hear yah on the on the whole 8025 controller deal. I'm hoping the next machine I pick up is a newer haas.

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