Re: Setting up end mills for CNC, and other things.

Hi Fitch,

Interesting observation, but not generally correct. Granted, the
large diameter end mill will have lower rpm and assuming the same
chip load (wrong assumption) it would be slower around the part.

The chip load and depth of cut could be much higher on the larger
diameter cutter and because of it's wider swath it's removing more
material, which equals more material removal per unit of time.

I think you'll find the overall job times will be lower if you get
the habit of using as large an end mill as your machine will handle
provided it can get into all the nooks and crannies of your part's
profile. Surface finish will be better with the larger cutter, also.

What're you making?

thanks,

Doug

--- In CAD_CAM_EDM_DRO@y..., Fitch R. Williams <frwillia@p...> wrote:
(snip)
> First an observation: I was interested to learn while playing with
the
> speeds and feeds calculator that within the constraints of surface
> speed of the cutter (I happen to be using all HSS end mills) staying
> constant, and number of flutes staying the same, when profiling
around
> a part, it is apparently faster to use the smallest end mill that
can
> safely make the required depth of cut.
>
> Why is this I wondered? I constructed the following answer for
> myself. The smaller mill makes more cuts per second at its given
> surface speed because the cutter lips are closer together for the
same
> number of flutes, so it can be fed faster while carrying the same
chip
> load (say .002" per lip). I guess this shouldn't surprise me, I
just
> hadn't run into it before using a manual mill with an un calibrated
> potentiometer setting the feed.
>
(snip)