Awl--

I'm starting to get involved with making low-end turning tools, and have a
few Qs regarding how people actually use them, and relative merits of
design.

For example, so far I've made simple left-hand cutting tools, with
triangular screw-type inserts, .600 vertex-to-vertex, about 1/8 thick.
Now I"m making boring bars with clamp-type triangular inserts.

I would think that for general cutting, square or even round (which I've
seen in use on huge "wheel truing" machines), would give the most bang for
one's cutting buck, in terms of overall usable cutting edges/points.
Generally speaking, of course, as certain shapes are better for certain
jobs--facing, threading, etc.
Do job shops use round inserts? Why/why not?

I'm also curious about clamping vs. screwing insert.
What are the pros/cons of these methods?
I would imagine the insert w/ a hole is more expensive, but the tool itself
is easier to make, and it seems that a thru-screw is more secure than a
clamp.
But mebbe holding power is less of an issue, than, say, in an
endmill/toolholder.

Thoughts?
--
------
Mr. P.V.'d (formerly Droll Troll), Yonkers, NY

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Absolutely Vote, but NOT for a Democrat or a Republican.
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all d'numbuhs

Tried the round ones on various occasions, both on mills and lathes
and I wasn't very impressed. Problem is that its impossible to have
an optimum chipbreaker on a round insert so you are limited to free
cutting steels. I also found that I go only about two edges out of
each one due to fracturing. While they can flexibly cut in any
direction I feel that they are a specialty tool as they set a lower
limit to your edge radius.

From comments on this board and elsewhere there is little consensus on
the clamping issue. I like the center-hole cam-lock style but others
hate it.

The first tool I always reach for is a triangular insert . All the
others are for special situations.

I have a peeve with fancy boring bars when I crash the tool and the
seat breaks to protect the inset.

starbolin

Proctologically Violated©® wrote:
Awl--

I'm starting to get involved with making low-end turning tools, and have a
few Qs regarding how people actually use them, and relative merits of
design.

For example, so far I've made simple left-hand cutting tools, with
triangular screw-type inserts, .600 vertex-to-vertex, about 1/8 thick.
Now I"m making boring bars with clamp-type triangular inserts.

I would think that for general cutting, square or even round (which I've
seen in use on huge "wheel truing" machines), would give the most bang for
one's cutting buck, in terms of overall usable cutting edges/points.
Generally speaking, of course, as certain shapes are better for certain
jobs--facing, threading, etc.
Do job shops use round inserts? Why/why not?

I'm also curious about clamping vs. screwing insert.
What are the pros/cons of these methods?
I would imagine the insert w/ a hole is more expensive, but the tool itself
is easier to make, and it seems that a thru-screw is more secure than a
clamp.
But mebbe holding power is less of an issue, than, say, in an
endmill/toolholder.

Thoughts?


Dude!

You gotta buy some of these tools and use them, before you get too
deep into trying to reinvent things. Triangle inserts, actually, give
the most usable corners per buck (6), despite what you might think about
squares. The key word there is "usable". A square has more actual
places that look like corners and cutting edges, but damned few places
where those will do you any good. The reason is that you simply can't
put a square insert into a corner of any kind, any where, by any means.

(Actually, you could try to do that if you mounted it square in the
holder; but then it would squeak and squeal and smoke itself to death,
and kill the workpiece too, on account of having no back clearance in
either direction, no matter which way you want to go. But even THAT
won't work if your tool needs a negative rake, 'cause then all those
nice square corners get to be more than 90 degrees when they're
presented to the work, and then a square won't do ANY cut that involves
even the least little hint of a shoulder, step, or change in cutting
attitude.)

A triangle, on the other hand, can be mounted for facing (including
into coreners), or for turning (including into corners), and will do a
halfway decent job with either, since it has 30 degrees of back
clearance built right into every corner. The trouble, however, is that
said 30 degrees of back clearance makes the triangle a pretty wimpy tool
if you try to go in whichever direction it's not mounted for. A turning
tool won't face much more than the size of the tool's corner radius. If
you try that, you'll get work and pressure on the back side of the
corner, and kill in insert pronto. Ditto when trying to turn with an
insert set up for facing. So, a triangle's more useful than a square;
but you'll always need two of them (one each for facing and turning),
which takes more time to set up, uses up valuable spots on your turret
or gang table, and thereby falls slightly short of wonderful.

Round inserts are great, if you don't mind trying to cut stuff with
a big, giant, chatter creating radius that won't go into any corner
smaller than itself. 50,000 pound machines trying to put 16 RMS
finishes on hardened steel faces with interrupted cuts would be a good
application for a round. Some formed grooves and extreme contours are
nice, too, if you can find a round small enough, and if you need more
sidewise guts than you'd get with a full-rad grooving tool. But those
situations aren't part of the fat, well populated middle of the bell
curve, if you know what I mean.

So, what's left? And what's really the most BANG for your
hard-earned dollars? Glad you asked. It's the insert of choice for
jobbers, and for production peoples too. It's for folks with simple
jobs that need quick setups and the fewest tools possible, and also for
complex jobs where even 18 or 24 tool stations can get filled up in a
hurry if you can't do more than one thing with some of your most basic
workehorse type tools. I refer, of course, to the 80 degree diamond.

80 degree diamonds can turn, with a built-in 5 degree back
clearance. They can face, with a built in 5 degree back clearance.
They can take heavier cuts than triangles, too, since they're nice
strong shapes, having only 5 degrees of back clearance (instead of 30)
in either direction. (Did I mention the part about the 5 degrees of
back clearance? That's a really nice feature.) And they can do all of
that, all by themselves, without needing a twisted twin like the
triangle, a follow up tool for corners, like the lowly square, or a
zillion pounds of iron to prevent chatter, like the rounds. Hell, an 80
degree diamond can even do some decent inside out facing (on account of
that now famous 5 degrees of back clearance) - like along an OD into a
nice tight corner, and then up a face to a bigger OD, and then around a
nice, neat convex corner break, and then on to some more OD turning,
without ever stopping to rest! Amazing!

And, if all that weren't enough, diamond inserts come with four
corners built right in, and four MORE corners, for free, if you turn
them into big-lead-angle milling inserts after they've done their turn
at turning. There are even standard, off the shelf milling cutters
specifically made for that very purpose! What more could you ask for??

Do diamonds, Dude. Dey's delighful!

KG

On Thu, 02 Aug 2007 22:52:58 -0400, Kirk Gordon
wrote:

Proctologically Violated©® wrote:
Awl--

I'm starting to get involved with making low-end turning tools, and have a
few Qs regarding how people actually use them, and relative merits of
design.

For example, so far I've made simple left-hand cutting tools, with
triangular screw-type inserts, .600 vertex-to-vertex, about 1/8 thick.
Now I"m making boring bars with clamp-type triangular inserts.
snip
Thoughts?


Dude!

You gotta buy some of these tools and use them, before you get too
deep into trying to reinvent things.
snip lots of good advice
Do diamonds, Dude. Dey's delighful!

KG
==============
Kirks's observations are spot on.

In high volume commercial use, competitive pressures on both the
tool manufacturers and end users have forced development and
deployment of optimal designs, with the important proviso that
the environment is high volume manufacturing with the
requirements of minimal down time (to sharpen tools, etc.),
immediate production with minimal set-up time [think SMED] and
repeatable/consistent results.

"Machine Shop Practice -- Vol I 2ed, Chapter 7 (Single Point
Cutting Tools and their Performance) pages 161-220" by Moltrecht
has a very detailed discussion of lathe type tooling.
Click on
http://www.industrialpress.com/en/Bo...3/Default.aspx
vol II
http://www.industrialpress.com/en/Bo...4/Default.aspx
(Get both volumes - you will use them.) Enco, Amazon and others
have these at discount.

Another useful reference source is the voluminous sales brochures
and web sites of the insert and tooling manufacturers.

Specialty tool and holder development/adaptation/extension for
non-commercial, low volume repair, model, prototype, and
home/hobby shop may be possible. One example is the tangential
type tool holders such as
http://www.bay-com.com/index.php?mai...b5a93620d80b8a
Note that this is a tangential tool *HOLDER*; the cutting action
is still radial. Horner [see below] shows a similar holder using
round tools. It should be possible by selecting the angle of
inclination to produce an 80-degree diamond using a square tool
bit, and even generate back/side rake as long as the top angle is
consistent. Of course the drawback is the use of HSS in a
cnc/carbide operation, but the tooling cost would be lower, and
with a proper jig/fixture quick to sharpen (just take a little
off the end at the proper [compound] angle)

Some of our posters that still operate screw machines (or have
good memories) may wish to comment on true tangential
tooling/tools such as skivers or roller back shave tools. Some
manufacturers are
http://www.championscrew.com/schiltter.htm
http://www.sommatool.com/


You might also take a look at the KRF Omnipost quick-change tool
system, which has a holder, designed to hold large carbide
inserts for use on smaller home/hobby lathes.
http://www.krfcompany.com/holderCarbide.html
http://www.krfcompany.com/
I doubt this is cost effective unless you luck into a cheap/free
supply of inserts, as most of the smaller lathes don't have the
power/speed/rigidity to fully utilize carbide, and most are
happier with high rake tooling.

Another area of information are (reprints of) the older machining
books as these have examples of tools and tooling that have
fallen from favor, but which you may adapt. Many of these are
from the depression era when labor was cheap and tools expensive
so are optimized to use inexpensive forms of tools [i.e.
rounds/rods] and to use up as much as possible of the tool.
One that comes to mind is "Practical Metal Turning p354-370" by
Horner.ISBN1-55918-277-6
A good source of these reprints is
http://lindsaybks.com/prod/allbks.html
Lindsay does not appear to have Horner in stock but you might try
http://www.abebooks.com/servlet/Sear...sts=t&y=5&x=50

Good luck and let us know what you discover/invent.

Unka' George [George McDuffee]
============
Merchants have no country.
The mere spot they stand on
does not constitute so strong an attachment
as that from which they draw their gains.

Thomas Jefferson (1743-1826),
U.S. president. Letter, 17 March 1814.

For lathe work I like the trigon, 6 corners & will do the same as an
80 deg diamond except maybe not take as deep a cut.

I second the trigon insert. My primary and prefered insert geometry.
Facing, turning, boring, and a large percentage of the profiling that I do.

--
Remove "nospam" to get to me.

On Thu, 02 Aug 2007 22:52:58 -0400, Kirk Gordon wrote:

Dude!

You gotta buy some of these tools and use them, before you get too
deep into trying to reinvent things. Triangle inserts, actually, give
the most usable corners per buck (6),

6 is 8?

despite what you might think about
squares. The key word there is "usable". A square has more actual
places that look like corners and cutting edges, but damned few places
where those will do you any good. The reason is that you simply can't
put a square insert into a corner of any kind, any where, by any means.

Sure you can. Just use the right TNR & toolholder for it.
They are rather good for roughing too.

(Actually, you could try to do that if you mounted it square in the
holder; but then it would squeak and squeal and smoke itself to death,
and kill the workpiece too, on account of having no back clearance in
either direction, no matter which way you want to go. But even THAT
won't work if your tool needs a negative rake, 'cause then all those
nice square corners get to be more than 90 degrees when they're
presented to the work, and then a square won't do ANY cut that involves
even the least little hint of a shoulder, step, or change in cutting
attitude.)

They are find for many applications. Were you correct few
would be sold & that's not the case.
They work for millng too g.

A triangle, on the other hand, can be mounted for facing (including
into coreners), or for turning (including into corners), and will do a
halfway decent job with either, since it has 30 degrees of back
clearance built right into every corner. The trouble, however, is that
said 30 degrees of back clearance makes the triangle a pretty wimpy tool
if you try to go in whichever direction it's not mounted for.

Planning is a good idea.

A turning
tool won't face much more than the size of the tool's corner radius.

It will.

If you try that, you'll get work and pressure on the back side of the
corner, and kill in insert pronto.

Go in the correct direction.

Ditto when trying to turn with an
insert set up for facing.

Misuse of tools is not an excuse to misuse them.

So, a triangle's more useful than a square;
but you'll always need two of them (one each for facing and turning),
which takes more time to set up, uses up valuable spots on your turret
or gang table, and thereby falls slightly short of wonderful.

Depends on making money.

Round inserts are great, if you don't mind trying to cut stuff with
a big, giant, chatter creating radius that won't go into any corner
smaller than itself. 50,000 pound machines trying to put 16 RMS
finishes on hardened steel faces with interrupted cuts would be a good
application for a round. Some formed grooves and extreme contours are
nice, too, if you can find a round small enough,

There are specific tools for such profiing with round (button) inserts IIRC.

and if you need more
sidewise guts than you'd get with a full-rad grooving tool.

Inserts should be supported by the proper toolholders.

But those
situations aren't part of the fat, well populated middle of the bell
curve, if you know what I mean.

So, what's left? And what's really the most BANG for your
hard-earned dollars? Glad you asked. It's the insert of choice for
jobbers, and for production peoples too. It's for folks with simple
jobs that need quick setups and the fewest tools possible, and also for
complex jobs where even 18 or 24 tool stations can get filled up in a
hurry if you can't do more than one thing with some of your most basic
workehorse type tools. I refer, of course, to the 80 degree diamond.

About the most expensive insert with the fewest *usable* edges,
usually.

80 degree diamonds can turn, with a built-in 5 degree back
clearance. They can face, with a built in 5 degree back clearance.
They can take heavier cuts than triangles, too, since they're nice
strong shapes, having only 5 degrees of back clearance (instead of 30)
in either direction. (Did I mention the part about the 5 degrees of
back clearance? That's a really nice feature.) And they can do all of
that, all by themselves, without needing a twisted twin like the
triangle, a follow up tool for corners, like the lowly square, or a
zillion pounds of iron to prevent chatter, like the rounds. Hell, an 80
degree diamond can even do some decent inside out facing (on account of
that now famous 5 degrees of back clearance) -

Check the toolholder & the resultant insert+toolholder geometry.

like along an OD into a
nice tight corner, and then up a face to a bigger OD, and then around a
nice, neat convex corner break, and then on to some more OD turning,
without ever stopping to rest! Amazing!

And, if all that weren't enough, diamond inserts come with four
corners built right in, and four MORE corners, for free, if you turn
them into big-lead-angle milling inserts after they've done their turn
at turning. There are even standard, off the shelf milling cutters
specifically made for that very purpose! What more could you ask for??

Being able to actually fully use those is rare.

Do diamonds, Dude. Dey's delighful!

--
Cliff

On Fri, 03 Aug 2007 11:10:21 -0500, F. George McDuffee
wrote:

sharpen (just take a little
off the end at the proper [compound] angle)

Then there's form-relieved ...
--
Cliff