I have a 1986 720 interact that the z axis does not mill flat. Does anyone know if there is a gibb adjustment on the head or any other adjustment that might help?

Many years ago I installed a 720 where the customer wanted to machine vacuum plates. Using the leveling screws you can affect the relationship between the head and the column. In other words you can achieve a very flat relationship between the table and the spindle. You check this by sweeping a circle with a indicator in the spindle.
In this case as the machine was used and heated up the squareness was lost. It turned out that the heat from the spindle motor went into the head and made it grow in an un-even fashion. The fix was to make an insulator plate between the spindle motor and the head.
How far out is your head out of square?
This is a machine that must be 15 years old. It may indeed have a wear issue.

George

George thanks for the reply. I believe I have found the problem. It was not the head it was a vise that was moving under load. I could indicate the bottom of the vise or any part I had clamped in it and it would indicate flat across the top of the part or bottom of vise but when I took a cut I would get a variation of depth in z by about .01 over 8". So I clamped the part directly to the table and it milled flat. You know this machine it's at B & W. I also have a communication issue I need to talk about if you could give me a call at your convenience I would appreciate it.
Thanks
Perry

Hello Perry!
I have mentioned your old BOSS machine on this forum as well. When was the last time you blew a transistor on that machine? (Knock on wood).

George

Well I'll knock on wood several times because it's been several years since one of those transistors blew. Believe it or not we still run that machine on a regular basis about 10-15 hrs a week most weeks.
Thanks
Perry