Posted by BillS on March 07, 2010 at 13:43:05:
In Reply to: Machining ab2 on gleason 12 posted by Mike on March 06, 2010 at 02:26:47:
Is it primarily the bottom cutter? This one usually takes a beating. It makes the "roughing" plunge cut and its tip will dull first.
Try slowing down the cutting speed, increasing cutter positive rake angle, and don't use flood oil-type coolant. You don't want lubricity on the bronze, but it does need coolant. Can't use water soluable coolant on the old Gleasons. You might try directed air or mist coolant along with slower cutting speeds.
Clacker boxes must be "stiff" on cutting stroke. Also workpiece holder must be very rigid. Bronze is its own lubricant, and will resist early chip formation.
Until the chip starts to "split", the sharp cutting edge is taking all the friction and heat. Once the chip begins to split, contact of chip with cutter moves back, away from the cutting edge. Dead sharp cutter with additional positive rake improves early chip formation and reduces friction at the cutting edge.
There is an optimal rake angle for bronze but I don't have it. And you don't want the top rake surface to be hollow ground.
Just some thoughts.