I just made my own lathe toolholder for indexable carbide inserts out
of a perfectly sized piece of aluminum I had lying around. I matched
the height of the cutter to a regular toolholder I have. I filed the
recess for the carbide and drilled and tapped the 4-40 hole for the
screw that secures the carbide. I copied the rough dimensions off of
some other tools I have seen and a carbide tooholder for a Amaco brake
lathe. My main question is what is the acceptable overhang of the
carbide over the toolholder. I know the carbide is brittle, and as I
was generously given the carbide inserts I really don't want to break
them. The current overhang is about 3/32" of an inch, but the one I
was copying from had less than 1/16" The brake lathe is designed for
ultimate rigidity, and I don't need quite that much accuracy, but I
don't want to be snapping carbides either.
Thanks,
Woodworker88 and the Los Altos High School Robotics Team #114
www.lahsrobotics.org

On 20 Oct 2005 20:03:35 -0700, "woodworker88"
wrote:

I just made my own lathe toolholder for indexable carbide inserts out
of a perfectly sized piece of aluminum I had lying around. I matched
the height of the cutter to a regular toolholder I have. I filed the
recess for the carbide and drilled and tapped the 4-40 hole for the
screw that secures the carbide. I copied the rough dimensions off of
some other tools I have seen and a carbide tooholder for a Amaco brake
lathe. My main question is what is the acceptable overhang of the
carbide over the toolholder. I know the carbide is brittle, and as I
was generously given the carbide inserts I really don't want to break
them. The current overhang is about 3/32" of an inch, but the one I
was copying from had less than 1/16" The brake lathe is designed for
ultimate rigidity, and I don't need quite that much accuracy, but I
don't want to be snapping carbides either.
Thanks,
Woodworker88 and the Los Altos High School Robotics Team #114
www.lahsrobotics.org

You should have none of the bottom of the insert overhanging. It
should be completly supported.

That being said...try to keep overhang as absolutly small as possible.

Gunner

"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner

Different inserts have different properties. Some are much tougher
than others by a factor of 2, 3 or more. Some work very well on one
material but not others. Do a web search and see what you have.

Also there's an old machinist's trick. Put piece of soft material
(0.010" soft copper works well) between the shim and the steel tool
holder.

Sounds good, guys. Since the overhang is slight now but I don't want
to redrill and tap the screw, I think I'll put a small sheet aluminum
or brass shim under the insert that will support it to the edge. This
won't be much of a height problem because I made the toolholder just a
tad too short to be centered when in the lathe.

woodworker88 wrote:

www.lahsrobotics.org

Nice site. I see LAHS has assumed ownership of the MVHS Eagle as mascot.
Does that make me an Alumni for LAHS? G (MVHS, class of '75)

Seriously, it's nice to see your robotics program in a school in this
day and age. Sure wish there'd been something like that when I was in HS.

Jon

all carbide tool holders I have support the carbide with a second piece of
carbide below it - this second piece of carbide is not sharp and doesn't
cut, it's only job is to support the cutter.
"woodworker88" wrote in message
oups.com...
I just made my own lathe toolholder for indexable carbide inserts out
of a perfectly sized piece of aluminum I had lying around. I matched
the height of the cutter to a regular toolholder I have. I filed the
recess for the carbide and drilled and tapped the 4-40 hole for the
screw that secures the carbide. I copied the rough dimensions off of
some other tools I have seen and a carbide tooholder for a Amaco brake
lathe. My main question is what is the acceptable overhang of the
carbide over the toolholder. I know the carbide is brittle, and as I
was generously given the carbide inserts I really don't want to break
them. The current overhang is about 3/32" of an inch, but the one I
was copying from had less than 1/16" The brake lathe is designed for
ultimate rigidity, and I don't need quite that much accuracy, but I
don't want to be snapping carbides either.
Thanks,
Woodworker88 and the Los Altos High School Robotics Team #114
www.lahsrobotics.org

Thanks for checking out our site. We try to create a robotics
experience in which people become better educated in the skills that
are important in the world right now. These skills help people get
jobs and have training they might not otherwise have.
As the student in charge of our machinery and the shop, I help the team
with the maintainence and operation of an Excello mill, a craftsman
lathe, a clausing drill press, and many other large and small tools.
In addition to routine maintainence and operation, we have worked on
everything from calibration and adjustment to fabricating replacement
parts. I hope that we will continue to get the funding we need to
maintain our team and continue to acquire new tools and skills.

According to Gunner :
On 20 Oct 2005 20:03:35 -0700, "woodworker88"
wrote:

I just made my own lathe toolholder for indexable carbide inserts out
of a perfectly sized piece of aluminum I had lying around. I matched
the height of the cutter to a regular toolholder I have. I filed the
recess for the carbide and drilled and tapped the 4-40 hole for the
screw that secures the carbide. I copied the rough dimensions off of
some other tools I have seen and a carbide tooholder for a Amaco brake
lathe. My main question is what is the acceptable overhang of the
carbide over the toolholder. I know the carbide is brittle, and as I
was generously given the carbide inserts I really don't want to break
them. The current overhang is about 3/32" of an inch, but the one I
was copying from had less than 1/16" The brake lathe is designed for
ultimate rigidity, and I don't need quite that much accuracy, but I
don't want to be snapping carbides either.
Thanks,
Woodworker88 and the Los Altos High School Robotics Team #114
www.lahsrobotics.org

You should have none of the bottom of the insert overhanging. It
should be completly supported.

And in particular, the better insert toolholders (both turning
and threading) tend to have an anvil of carbide to offer better support
than the unhardened steel can offer. If you want to make a really
*good* toolholder, but a couple of spare anvils, and the hardware for
attaching it (sometimes a screw with a cylindrical post for orienting
the insert properly -- if the insert has a center hole, or sometimes a
flat-head screw designed to be flush with the top of the anvil, if the
insert has no center hole, and is designed to be supported purely by
being clamped in place -- often with a chipbreaker on top of it.

The cheap toolholders will often distort when an overloaded
insert breaks, and this offers less support for the next insert, making
it break at a lesser load than the previous one broke at.

I think that the anvils are a tougher (less brittle) form of the
carbide than some of the inserts (depending on what the inserts were
made to cut.)

That being said...try to keep overhang as absolutly small as possible.

Agreed.

Enjoy,
DoN.

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According to :
Also there's an old machinist's trick. Put piece of soft material
(0.010" soft copper works well) between the shim and the steel tool
holder.

O.K. That would be an alternative to the carbide anvil which I
just suggested in another branch of this thread. It would deform easily
enough to bed into any imperfections in the pocket in the holder, and
provide better support than a tough steel would, and is easy to replace
when you replace the insert.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---