Hi,
I need to cut quite a few 1" thick aluminum parts for my DIY CNC router. I tested a 1/4" diameter 1-1/4" flute length single flute carbine end mill from tools today. I used G-Wizard to calculate all parameters of the cut making sure to be as conservative as possible the first time. My work was clamped directly to the surface of the machine which is an industrial 5' x 10' router made by AXYZ. There was minimal vibration in the cut as this is such a large machine and the work was clamped well.
I broke two cutters at the top of the flute where the shank meets the flutes. Both times happened within a minute of cutting. The second one broke just touching the material with a very slow plunge rate. I should note it was a straight plunge and not a sprial or other type. Blew around $100 in a half hour. Before I cut again I need to figure out a new plan.
I'm wondering why this happened. After I moved to a much shorter bit with a flute length of 3/8" made by onsrud, I cut 20 1/4" thick parts quite aggressively with no issues. The tool looks like it has much life left in it. I was cutting at 1/8" DOC and a 40 in/min feedrate and 18000 RPM. I was cutting with constant compressed air and a generous amount of WD-40 in this cut and my failed attempts.
So either the vibrations induced in the machine were too high for that cutter length, and caused it to break pre-maturely. Or onsrud makes better bits than tools today. All aluminum cutting bits I used in high school were onsrud and I never experienced breaks like this. The bits just seemed to keep on going without fault.
If the 1-1/4" cutter doesn't work for me, would it be possible for me to use a cutter with say a 1/2" flute length to cut 1" deep? As long as the shank matches the flute diameter to allow it to enter the cut the flutes have made, and I can successfully clear all chips using compressed air, I should be good right?
Perhaps a 2 flute carbide is preferable?
All input appreciated.
Thanks,
Matthew