2-flute carbide router bit. Wanting to make some some 1/4" deep scallops in a project.
Survey of the Carbide3D 3-flute feeds and speeds chart, the Shapeoko wiki materials page, and a CNC Cookbook page has surface speeds for MDF of ~1100 SFM, 1036 SFM, and 1500 SFM.
With a 3/4" bit at 10,000 rpm (slowest my Makita will go), that’s ~1964 SFM. Since I’m only going 1/4" deep, I won’t hit the full diameter, but instead about 0.707". Which works out to a surface speed of ~1851 SFM. I saw Winston using a 3/4" bowl bit in his walnut catch-all tray video, so I’m assuming the extra surface speed is not a big deal (unless the differences between walnut and MDF are somehow going to screw things up, such as the resin in the MDF).
This page from GDP Tooling recommends a 0.025" chipload for MDF with cutters 1/2" and larger:
Dumping 10k rpm, 2 flutes, and 0.025" chipload into my chipload spreadsheet yeilds a feedrate of 500 IPM (over 8 IPS)! From what I read / calculated, the max speed of the Shapeoko is just under 200 IPM (over 3 IPS) based on Grbl settings. Don’t think I’ll be trying that kind of feed either.
Can someone recommend a less ridonculous chipload for this size cutter on the Shapeoko? 1/4" cutters have chiploads in the 0.0016 to 0.0017" range for MDF on the Shapeoko. If I plug in that chipload for the 3/4" cutter, feed comes out to a much more reasonable-sounding 33 IPM. Doubling the chipload to 0.0033" doubles the feedrate to 66 IPM.
I’m tempted to start with the 33 IPM. Can anyone chime in on practical experience with 3/4" cutters in MDF on the Shapeoko?