I have some 1/2" turning tools that I use on my 9 x 20 lathe.

They have triangular inserts that measure about .625" x .160" thick,
with a positive rake, a chip breaker, a very small radius and are not
coated.

They attach to the tools with a countersink head screw.

I don't see anything to identify them but I would like to find
something that would work better. It seems that they lose their edge
rather quickly and don't leave as good a finish as I would like.

Mostly I'm cutting HRS or CRS and sometimes A2. No 'production' here,
I'm just a hobbyist.

Do you have a suggestion for an insert that might work better for what
I'm doing?

TIA.

Lewis.

*****

In article
,
" wrote:

It seems that they lose their edge
rather quickly and don't leave as good a finish as I would like.

Mostly I'm cutting HRS or CRS and sometimes A2. No 'production' here,
I'm just a hobbyist.


Non-production and (especially) looking for better finish would lead me
to dump carbide and inserts (production tooling) in favor of M-2 or
cobalt HSS bits, ground by hand.

--
Cats, coffee, chocolate...vices to live by

wrote:
I have some 1/2" turning tools that I use on my 9 x 20 lathe.

They have triangular inserts that measure about .625" x .160" thick,
with a positive rake, a chip breaker, a very small radius and are not
coated.

They attach to the tools with a countersink head screw.

I don't see anything to identify them but I would like to find
something that would work better. It seems that they lose their edge
rather quickly and don't leave as good a finish as I would like.

Mostly I'm cutting HRS or CRS and sometimes A2. No 'production' here,
I'm just a hobbyist.

Do you have a suggestion for an insert that might work better for what
I'm doing?

TIA.

Lewis.

*****


Carbide needs a high surface speed to get a good finish. On carbon
steel you should be able to run at least 500 SFM and higher. Make sure
you tool hight is properly set on center. Coolant helps for a good
finish. HSS will give you a good finish at lower surface speeds. Hone
the edge of the tool after grinding.

Also with carbide grade you have for the insert may not be the right one
for the material you are cutting. The insert you are using is probably
a TPGT series but as to what size, you should get your hands on a insert
catalog or go serch the TPGT on the internet.


John

"john" wrote in message
...
wrote:
I have some 1/2" turning tools that I use on my 9 x 20 lathe.

They have triangular inserts that measure about .625" x .160" thick,
with a positive rake, a chip breaker, a very small radius and are not
coated.

They attach to the tools with a countersink head screw.

I don't see anything to identify them but I would like to find
something that would work better. It seems that they lose their edge
rather quickly and don't leave as good a finish as I would like.

Mostly I'm cutting HRS or CRS and sometimes A2. No 'production' here,
I'm just a hobbyist.

Do you have a suggestion for an insert that might work better for what
I'm doing?

TIA.

Lewis.

*****


Carbide needs a high surface speed to get a good finish. On carbon steel
you should be able to run at least 500 SFM and higher. Make sure you tool
hight is properly set on center. Coolant helps for a good finish. HSS
will give you a good finish at lower surface speeds. Hone the edge of the
tool after grinding.

Also with carbide grade you have for the insert may not be the right one
for the material you are cutting. The insert you are using is probably a
TPGT series but as to what size, you should get your hands on a insert
catalog or go serch the TPGT on the internet.


John

Mild steel is less than desirable where surface finish is concerned.
Expecting a decent finish is a bit of a stretch, especially if you take
shallow cuts. It likes to tear, and rarely machines with a decent finish.
Running fast enough with carbide, and an acceptable depth of cut changes
that, but it's not within reason to expect small machines to have the
capability to perform to that standard. They generally don't provide the
required rigidity or power.

You really should investigate HSS and learn how to grind your own. I'm not
suggesting that you would have better results than with carbide where
surface finish is concerned, but the overall picture will improve
drastically if you master the art of grinding your own tools. There are
many instances were HSS will outshine carbide, especially on small machines,
where the advantage of using carbide is lost.

Harold

On 2009-09-21, john wrote:
wrote:
I have some 1/2" turning tools that I use on my 9 x 20 lathe.

They have triangular inserts that measure about .625" x .160" thick,
with a positive rake, a chip breaker, a very small radius and are not
coated.

Hmm ... the normal way to size inserts is by the "IC" (inscribed
circle) approach. What is the largest diameter circle which will fit
within the triangle without sticking out over the sides.

Then get a MSC catalog (if you don't already have one) and you
will find charts for identifying inserts by numbers.

They attach to the tools with a countersink head screw.

That sounds like the cheap sets of five with a full left, an
angled left, a straight ahead, an angled right and a full right.

These tend to use thinner inserts, and to have no carbide anvil
under the inserts, so they break fairly easily -- even if you have the
right grade (IIRC, C2 and C5 are the two grades offered in this style,
and I forget which works best with which material -- but steel,
aluminum, and cast iron each have their own preferences.

I don't see anything to identify them but I would like to find
something that would work better. It seems that they lose their edge
rather quickly and don't leave as good a finish as I would like.

That sounds like the cheap ones -- and TiN coating won't make
much difference.

Mostly I'm cutting HRS or CRS and sometimes A2. No 'production' here,
I'm just a hobbyist.

Do you have a suggestion for an insert that might work better for what
I'm doing?

Well ... what I tend to prefer is negative rake inserts with a
chipbreaker which makes them into effectively positive rake tools. I
use the Aloris BXA-16N holder (which has space for two inserts, one for
turning, and the other for facing). In that size holder, I use the
following inserts:

Quant Order # Pr.Ea. Description
2 pk LX07080062 $15.90 TNMG-322 C6 TiN NN60 pkg 10

If you are using an Aloris style quick-change toolpost on your lathe, I
would expect it to be AXA size, not BXA, so you would have to find the
right size inserts for the AXA holder. The ones above were on sale back
in January of 2005 (so the price has likely changed), and I have not
used up many of them in that time -- perhaps three counting the ones
currently in the holder.

But -- when I want a nice finish -- the choices are either HSS
ground and polished nicely, or the smaller inserts which fit tool
holders which came with my Emco-Maier Compact-5/CNC (5" swing) lathe.
These are ground after forming and are not TIN coated, and as a result
have a very sharp edge.

The larger ones are better for serious metal removal.

Good Luck,
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 ---

"DoN. Nichols" wrote in message
...
snip

(IIRC, C2 and C5 are the two grades offered in this style,
and I forget which works best with which material -- but steel,
aluminum, and cast iron each have their own preferences.

C2 for cast iron and aluminum, plus 300 stainless.

C5 for steel and alloys.

Harold