I am using a 1/2" diameter, 2.5" cutting length straight bit to cut a guitar body with lots of 2D curves on 2" deep profiles (in four passes.) For now, I'm using MDF for prototyping. I need to eliminate the need to shape the part after cutting so the customer really just needs to sand down the roughness of the grain. However, whenever I cut the part, I get very noticeable bumps. I've correlated these to several factors:
1. I consistently get a bump where the circular lead ins meet the cutting line
2. There are bumps on either end of a zig-zag ramp lead in
3. Where the part gets close enough to the edge of the material that the bit cuts through the edge, there's a noticeable bump.
4. I think I can even attribute one bump to a ramped tab.
I think I can probably eliminate most of this by using spiral ramps and steering clear of the material edge. I won't be able to do away with tabs, but I'm not 100% sure about the tabs causing the bumps anyway.
I'm wondering though, should the spindle have that much play that a bit will move by ~1/16" based on what I would consider normal cutting forces?
Are there other factors at play that I can tweak to improve the smoothness of the cuts?
Thanks a lot!
Andy