Re: [CAD_CAM_EDM_DRO] Inserts R US

Hello Terry,
Possibly I misunderstood the word negative rake, That is the position against
the piece, right?
Positive rake first the tip hits the piece and then the flank
and negative other way round.?
I meant the cutting edge. On Aluminium you get into bad trouble if you use negative inserts.
My English I learned in factories and on the road. so more than one mistake is common
in my conversations, as well as in Spanish.
Good Luck
Sven Peter


Terry Toddy wrote:

> 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
>
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