[mack5555]

I am still in school and I have a question about finishing a mold with a .125 ball end mill.

The total depth of the part is 1" but everything else has been milled down and now I am just looking to finish the surfaces. The sides of the mold are already done just need to do all other surfaces.

So can I use a .125" ball end mill with only .5" flute length? The shank is also .125". I will need to leave the tool stick out 1.1" from the tool holder. Will there be to much deflection?

[txcncman]

You can use a ball mill of whatever flute length will be equal or greater than your depth of cut. If the total depth is 1" exactly, you only need to leave 1.001" clearance between the tool tip and the face of the holder. Since this is a mold, it would be assumed the sides are drafted. There are tools made just for mold making that take this into account. The amount of deflection obtained will be dependent on the actual tool used, the material being cut, and the speed, feed, and chip load, as well as the rigidity of the machine. I did some cutting with an 0.090" diameter extra length necked down end mill (0.850" stick out) yesterday and had to offset the cutter compensation by 0.0025" per side (0.005" on diameter) to account for deflection.

[mack5555]

Thanks for you suggestion.

[mack5555]

What type of step over would be the max for something like this .015"? for a little roughing and .005" for final?

[txcncman]

That would be a good starting point. You still never said what type of material you are cutting.

Oh, I forgot to mention tool engagement previously. I was cutting 6061 0.032" axle depth of cut and full diameter (0.090") radial depth of cut at 7 IPM turning 7500 RPM.

[mack5555]

1030.......6000 rpm.......8.5 ipm

[txcncman]

With a 4 flute ball mill, and your 0.015" DOC, this should work.