Re: [CAD_CAM_EDM_DRO] Inserts R US

Sven and Tom,
There are negative rake carbide inserts that actually have a positive
rake cutting geometry. The inserts are called negative rake because the
plane of the insert is held by the holder at a negative rake angle but
they provide a positive rake cutting edge with a chip breaker groove
around the cutting point. These are the style inserts I would reccomend
for production turning of aluminum. With negative rake inserts you get
twice as many usable points per insert compared with positive rake
inserts. This style also gives much better chip control. In production
turning you want the chips to break up into small pieces. Postive rake
single point tools without chipbreakers typically produce long stringy
chips that are dangerous and difficult to dispose of. Of course if you
are just taking a light finish cut neither style will do much about the
stringy chips.

If anyone is interested I can specify a specific insert.

Terry

"Sven Peter, TAD S.A." wrote:

> For aluminum never use negative inserts. It clogs up like hell and
> destroys your pieces.
> The special aluminum inserts are milled out of HSS-E tool steel with an
> extremely
> positive angle ( 40 degree chissle angle.)
> They are damn expensive.
> So you should try with a simple cobald steel with the following angles:
> free angle 10 deg.,
> chip angle 25 to35 deg. resulting chissle angle 45 deg.
> Personally for standard facing and roughing jobs I love 55 degree rombus
> inserts.
> (In steel DNMG ) they last long and do not break the tips.
> I hope this helps.
> Sven Peter
>
> Tom Eldredge wrote:
>
> > I just yesterday purchased a tool and insert combination to face finish
> > aluminum disks. It is a VNMG carbide insert, This tool holder has a
> > "negative rake", I think it is called.
>
> > How do I know just where the tool
> > should be vertically when turning on a lathe? Should the tool touch the
> > work exactly at the height of the center of the disk being cut? I suppose
> > this is elementary, but I hack things out on a taig lathe when I need them,
> > and I really do not know what is best.
> > Thanks again.
> >
> > Tom Eldredge