Re: plunging endmill (thanks)

Thanks Jon, and others who gave very valuable information offlist.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
>
>
> heroaku wrote:
>
> >Hi,
> >
> >I am very new to machining as well as to CNC and will like to ask
the
> >group about the advisability of plunging an endmill vertically
into a
> >workpiece. I am using the set of 6 endmill purchased from Sherline
> >(does these have cutting edges on its bottom)
> >
> >
> You can do this with center-cutting end mills. Some work better
than
> others at this.
> They generally don't, however, work as well as a regular drill bit.
>
> >Initially, I plan to cut only softer materials like wood and
plastic.
> >Do I need to program the cutter to enter tangentially, or is it
> >sufficient to plunge them straight vertically into the workpiece.
> >
> >
> Depending on the material characteristics, you generally can plunge
> straight in, with a
> center-cutting tool, but on brittle materials, it sometimes takes
so
> much infeed force
> that the material will crack. Plastic tends to melt quickly, and
you
> have to feed in slowly
> to avoid cracking. You may have to take small bites and then come
up
> for cooling and
> chip removal. Anyway, you will find that the plunging in needs to
be
> done at pretty slow
> feed rates, or the tool may fill with chips and make a mess.
>
> Jon