Rory wrote: Keep us posted on the deep pockets.
I forgot to update you about deep pocketing with a single flute endmill!
Here we are.
I have to say that I'm little bit disappointed by working on POM-C/Delrin with the single flute. The problem is not the quality of the horizontal surface but the rate of vibrations when going deep into the material for more than 5 or 4 millimeter.
I mean... it works but I hear some grrr-grrr noise. This noise has two phases:
1) when plunging vertically I hear a robust GRRRRRRR
2) after, when the endmill starts ti move horizontally, I hear grrr-grrr-zzzzzzzzzz, grrr-grrr-zzzzzzzzzz, and so on.
I strongly suspect that the main problem is the remarkable
asymmetry of the tip of a single flute endmill.
When it plunge down into the material it touches the surface only with the tip that is located far away from the central vertical axis of the tool, this cause a small deflection in my opinion. Deflection is not a big problem when the pocket is 2 or 3 mm deep, but for lower pocketing it happens that the position of the tool is not precise. When the tool starts moving along the walls of the pocket it is a little bit "pushed" against them, cause is not perfectly aligned. So the strange noise.
If the toolpath along the pocket-wall is long enough, after a while, the endmill "find" his road and the noise ends.
The same happens with less rigid diameters of the tool (i.e. 3mm)
Final evaluation (vote from 0 to 10) for single flute
Deep pocketing: vote = 6
Swing-cut/side milling: vote = 10
So, in my opinion, the single flute is absolutely superb/magnificent when you have to refine the external contour of a shape (as well as refining the internal walls of a deep box). No doubt, in this cases go for a single flute. It scratches the vertical surface like a knife and causes zero vibrations/noises.
In all other cases the two-flute is to be used, is more "smooth" in my opinion.
Final final final considerations
What above holds for Delrin/POM-C material, but I have tested the single flute on a more softer material like PE-300 (aka PE-HD) and I discovered that is really all-in-one end mill. You can use it for deep milling as well as for side milling with no problems.
PE300 has a density of 0.93 gr/cm3 (if I remember right) where POM-C is around 1.41 gr/cm3. So POM-C is much more harder and is not the best for an asymmetrical endmill.
As I said before, the profile of the bit that I used is shaped like the eagle's beak, maybe using a single-flute endmill from Onsrud results could be better (the tip of the endmill is completely flat). But this is only an idea/impression.
Tschussss!