Spindle speed for large diameter parts

[OlioMk]

Hi.
I am new into CNC Turning and i would like to ask about Spindle speed for large or massive parts.
We have a two axis CNC HAAS ST30.
So, if manufacturer of the tool inserts recommends minimal cutting speed of 244 m/min and i need to do face operation from 20 mm to 300 mm accross x axis (let say at Z=-1 mm), how to setup spindle speed in this situation? If i calculate N , at max value of x , which is 300 mm, i will have spindle speed of 260 1/min but same calculation at min x value of 20 mm will produce result of 3885 1/min. First, we don't have that much speed on our machine and second, not safe to turn hevy part at that rate. We are using G50 and G96 in our code.
What to do in order to have good chip breaking and stable work conditions?

[Jim Dawson]

Keep in mind that the insert manufacturer recommended speeds are suggestions for best results, but not hard rules. What I do is set G50 to the maximum allowable speed for the operation, and just run it. If you have G99 (Feed / Rev) it might be useful in this case.

[deadlykitten]

hy olio, large diameters may raise a few problems :

1) if they have not been cutted square before machinin, then is possible to have a lot of tir far away from chuck, and also very small footprint with the jaws, thus grip may be subjective

are you in this situation ?

2) cutting the od, with a tool that is facing down ( towards y- ) may raise&lower your turret ( at least the revolver head ) at each revolution ... when this phenomen is powerfull, you may see and hear it

this is why is said that a tool that is facing down has the tendency to disamble the turret, while a tool that is facing up has the tendecy to compress the turret

3) facing is easy :

G50 S500 rpm will never go above this value
G00 go to turret index position
T index turret
G96 S M3 M8
G00 X300+10 Z0 thus be at 5mm above 300
G01 X-2*tool_rad F G95 machine
G01 X0.3 Z0.15
stop rpm, go back to home position

4) cutting specs, you have to feel them i recomand you to begin with 75M/min, 0.2mm/o, doc 0.5-1 .... and increase them slowly, but not above the limit where you do not feel comfortable

it may be possible that someone will rush you, and in that moment is possible to do a mistake ...

What to do in order to have good chip breaking and stable work conditions?

some persons are face milling big diameters, so to avoid problems that appear when turning

when turning, go steady, perhaps use 1st gear of your spindle for more torque / kindly