Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound up,
wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Dec 26, 4:26*pm, Tim Wescott wrote:

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? *I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.

I use the micrometer carriage stop to keep the chuck and carriage
apart. The previous users didn't, repeatedly, but the lathe survived.

Jim Wilkins wrote:
On Dec 26, 4:26 pm, Tim Wescott wrote:
Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.

I use the micrometer carriage stop to keep the chuck and carriage
apart. The previous users didn't, repeatedly, but the lathe survived.

You can also clamp a piece of scrap keystock to the carriage to limit
longitudinal travel. Touch the cutter holder to the jaws with machine
off, then clamp the rod so it touches the headstock at the back, with a
..010 shim under the end.

On Fri, 26 Dec 2008 13:26:05 -0800, Tim Wescott wrote:

Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound up,
wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.

Make a set of guides (both sides of the work) and use a hacksaw. A
U-shaped piece with a slot mounted on the cross-slide - slot keeps the
blade from wandering, bottom determines the fin depth.

_ wrote:
On Fri, 26 Dec 2008 13:26:05 -0800, Tim Wescott wrote:

Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound up,
wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.

Can you mount the cylinder on an arbor?
That would give you a more secure mount than a 3-jaw chuck, and you
could get it away from the chuck. You could also stabilize it with the
tailstock.

Tim Wescott wrote:

Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound up,
wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.


I would recommend using coolant if possible. Make sure you have enough
side clearance on the cutoff tool.


John

john wrote:


Tim Wescott wrote:

Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound
up, wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.


I would recommend using coolant if possible. Make sure you have enough
side clearance on the cutoff tool.

I guess this is aluminum?
WD40 or kerosene works for cutting fluid.

RB wrote:

john wrote:



Tim Wescott wrote:

Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound
up, wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of
the chuck, out of paranoia about hitting the jaws with the tool holder.


I would recommend using coolant if possible. Make sure you have
enough side clearance on the cutoff tool.


I guess this is aluminum?
WD40 or kerosene works for cutting fluid.


One of the problems with parting is that the work and the tool heat up
and work grabs the tool. Coolant or some other way to get the heat out
is advisable.

John

"john" wrote in message
...


RB wrote:

john wrote:



Tim Wescott wrote:

Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound
up, wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.


I would recommend using coolant if possible. Make sure you have enough
side clearance on the cutoff tool.


I guess this is aluminum?
WD40 or kerosene works for cutting fluid.


One of the problems with parting is that the work and the tool heat up and
work grabs the tool. Coolant or some other way to get the heat out is
advisable.

John

Parting is one of the few places where lubricating oil is sometimes
recommended. I've tried it, and it works OK in steel. Since I use Buttercut
lard oil for most of my turning I don't notice much of a difference. The
lard oil works fine. I'm careful to have side clearance on my tools but
there's still a lot of friction in that type of cutting.

I don't think that kerosene is lubricious enough for parting or deep
grooving. WD40 might be, but it isn't much of a cutting fluid. It isn't much
of anything, for that matter, except a good cleaning fluid. I've found that
it's good for getting chewing gum out of your clothes. g

--
Ed Huntress

Ed Huntress wrote:

"john" wrote in message
...


RB wrote:


john wrote:



Tim Wescott wrote:


Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound
up, wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.


I would recommend using coolant if possible. Make sure you have enough
side clearance on the cutoff tool.


I guess this is aluminum?
WD40 or kerosene works for cutting fluid.


One of the problems with parting is that the work and the tool heat up and
work grabs the tool. Coolant or some other way to get the heat out is
advisable.

John


Parting is one of the few places where lubricating oil is sometimes
recommended. I've tried it, and it works OK in steel. Since I use Buttercut
lard oil for most of my turning I don't notice much of a difference. The
lard oil works fine. I'm careful to have side clearance on my tools but
there's still a lot of friction in that type of cutting.

I don't think that kerosene is lubricious enough for parting or deep
grooving. WD40 might be, but it isn't much of a cutting fluid. It isn't much
of anything, for that matter, except a good cleaning fluid. I've found that
it's good for getting chewing gum out of your clothes. g

--
Ed Huntress



On the cnc's with a lot of coolant I have no problem parting off 2.25
inch bars but on the manual machine not using coolant I have snapped a
blade or two. With coolant on the manual machines the blades work fine.

John

"Ed Huntress" wrote in message
...
snip-

I don't think that kerosene is lubricious enough for parting or deep
grooving.

It is the lubricant of choice.

Harold

On Fri, 26 Dec 2008 16:16:48 -0600, RB wrote:

john wrote:


Tim Wescott wrote:

Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound
up, wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.


I would recommend using coolant if possible. Make sure you have enough
side clearance on the cutoff tool.

I guess this is aluminum?
WD40 or kerosene works for cutting fluid.

It's steel. The Cox series of engines uses a one-piece cylinder finished
on the inside for a piston, threaded at each end for crankcase and head,
with 4 - 8 milling operations (one or two transfer ports, two or four
exhaust ports, and two on no flats for removing the cylinder).

Cutting fluid. Ha. That'll be a pain on my minimalist lathe (but it
sounds quite necessary).

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

"Tim Wescott" wrote in message
...
snip--

I guess this is aluminum?
WD40 or kerosene works for cutting fluid.

It's steel. The Cox series of engines uses a one-piece cylinder finished
on the inside for a piston, threaded at each end for crankcase and head,
with 4 - 8 milling operations (one or two transfer ports, two or four
exhaust ports, and two on no flats for removing the cylinder).


I thought it was aluminum, too. Forget the kerosene, it is restricted to
use on aluminum.

If you have access, use some of the old formulation Tap Magic (the one with
1,1,1, trichloroethane). There is no better lubricant for such an
operation. Same rules apply on the parting tool. If it makes contact
anywhere but at the point of the cut, you'll never get through the job. You
also won't have the same degree of success if you try to face the fins, but
it can be done. Keep the tool exceedingly sharp.

Harold

Tim Wescott wrote:
On Fri, 26 Dec 2008 16:16:48 -0600, RB wrote:

john wrote:

Tim Wescott wrote:

Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound
up, wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.


I would recommend using coolant if possible. Make sure you have enough
side clearance on the cutoff tool.
I guess this is aluminum?
WD40 or kerosene works for cutting fluid.

It's steel. The Cox series of engines uses a one-piece cylinder finished
on the inside for a piston, threaded at each end for crankcase and head,
with 4 - 8 milling operations (one or two transfer ports, two or four
exhaust ports, and two on no flats for removing the cylinder).

My bad, I assumed aluminum

On Mon, 29 Dec 2008 13:39:29 -0600, RB
wrote:

It's steel. The Cox series of engines uses a one-piece cylinder finished
on the inside for a piston, threaded at each end for crankcase and head,
with 4 - 8 milling operations (one or two transfer ports, two or four
exhaust ports, and two on no flats for removing the cylinder).

My bad, I assumed aluminum
================
After you have checked to make sure the gibbs/bearings/etc. are
tight, check
http://www.use-enco.com/CGI/INPDFF?P...MITEM=422-2880
http://www.use-enco.com/CGI/INPDFF?P...MITEM=422-2913
http://www1.mscdirect.com/CGI/N2DRVS...C-T7L391316886

Best tool in the box is usually an American Express card...

Use a .045 cut off blade for a 4-1/2" angle grinder, mounted on your
tool post grinder for the roughing-out. Then clean up with your
itty-bitty tool. Or make a mount to hold your angle grinder & use it
for the roughing.

I never said that I was a machinist,
Bob

Bob Engelhardt wrote:
Use a .045 cut off blade for a 4-1/2" angle grinder, mounted on your
tool post grinder for the roughing-out. Then clean up with your
itty-bitty tool. Or make a mount to hold your angle grinder & use it
for the roughing.

I never said that I was a machinist,
Bob

Well , I'm not a machinist either , though I sometimes play one out in the
shed . I was going to suggest a dremel tool , with a diamond cutoff wheel
and lots of lube - I'd think detergent and water might work well on this one
.... or WD40 .
Mounting it on an arbor (as mentioned above) would also help a lot ...
Was that a .15 or a .015 motor ?
--
Snag
every answer
leads to another
question

On Fri, 26 Dec 2008 16:59:23 -0600, Terry Coombs wrote:

Bob Engelhardt wrote:
Use a .045 cut off blade for a 4-1/2" angle grinder, mounted on your
tool post grinder for the roughing-out. Then clean up with your
itty-bitty tool. Or make a mount to hold your angle grinder & use it
for the roughing.

I never said that I was a machinist,
Bob

Well , I'm not a machinist either , though I sometimes play one out in
the
shed . I was going to suggest a dremel tool , with a diamond cutoff
wheel and lots of lube - I'd think detergent and water might work well
on this one ... or WD40 .
Mounting it on an arbor (as mentioned above) would also help a lot ...
Was that a .15 or a .015 motor ?

..15. Cox didn't make a .015 to my knowledge (although you could make a
de-bored cylinder for a .020, I suppose).

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

"Terry Coombs" wrote in message
.. .
Bob Engelhardt wrote:
Use a .045 cut off blade for a 4-1/2" angle grinder, mounted on your
tool post grinder for the roughing-out. Then clean up with your
itty-bitty tool. Or make a mount to hold your angle grinder & use it
for the roughing.

I never said that I was a machinist,
Bob

Well , I'm not a machinist either , though I sometimes play one out in
the shed . I was going to suggest a dremel tool , with a diamond cutoff
wheel

Bad idea. Diamond and steel are not compatible unless you keep surface speed
VERY slow. If you experience any heat near redness, it destroys the
diamond. Diamond grinding wheels are never advised for grinding steel.

Harold

In article ,
Tim Wescott wrote:

Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound up,
wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.

What kind of lathe are you using? Can you run backwards without causing
the chuck to unscrew? Or, can you hold the workpiece in a collet?

Anyway, what I discovered in my long saga with chattering cutoff tools
is that one big danger is self-feeding of tool into work. A very rigid
machine limits this, but not all machines are all that rigid. One
alternative is to turn the tool upsidedown and spin the work backwards,
so the cutting forces instead tend to pull the tool out of the work.
This will prevent grabbing due to self-feeding.

The other issue is to shape the cutting tool so it's max width at the
cutting edge and tapers as one goes away from the cutting edge. In
other words, the tool becomes slightly necked, prevent cutting on the
sidewalls of the groove. Make sure that everything is square and
locked, so the tool feeds straight into the groove without translating
into either sidewall.

And ensure that the groove is flooded with cutting fluid. A brush will
not do.

Now, I'm assuming that your lathe is tight. If not (and my lathe was
not tight at first), you must first fix the lathe. I must say one stark
moment was when I found that I couldn't make a 0.0625" wide slot in mild
steel using my 1500# lathe. I knew that this cannot be right, and
started the investigation. Everything that could be loose was loose.
Search past RCM postings for "Clausing 5914 chatter" and "Trepanning and
Parting Off" in the subject for the long sad saga.

Joe Gwinn

Joseph Gwinn wrote:

Now, I'm assuming that your lathe is tight. If not (and my lathe was
not tight at first), you must first fix the lathe. I must say one stark
moment was when I found that I couldn't make a 0.0625" wide slot in mild
steel using my 1500# lathe. I knew that this cannot be right, and
started the investigation. Everything that could be loose was loose.
Search past RCM postings for "Clausing 5914 chatter" and "Trepanning and
Parting Off" in the subject for the long sad saga.

Had a similar moment with my little 9" Logan, trying to part off a 1"
rod. It finally dawned on me that something was shifting, so I started
at the headstock mounts and worked my way through every joint up to the
tool, cleaning, shimming, re-torquing. Took an evening, but it's still
tight years later.

In article ,
RB wrote:

Joseph Gwinn wrote:

Now, I'm assuming that your lathe is tight. If not (and my lathe was
not tight at first), you must first fix the lathe. I must say one stark
moment was when I found that I couldn't make a 0.0625" wide slot in mild
steel using my 1500# lathe. I knew that this cannot be right, and
started the investigation. Everything that could be loose was loose.
Search past RCM postings for "Clausing 5914 chatter" and "Trepanning and
Parting Off" in the subject for the long sad saga.

Had a similar moment with my little 9" Logan, trying to part off a 1"
rod. It finally dawned on me that something was shifting, so I started
at the headstock mounts and worked my way through every joint up to the
tool, cleaning, shimming, re-torquing. Took an evening, but it's still
tight years later.

Also a neglected machine.

More saga at "Clausing 5914 - Chatter and Self-Feeding Summary" and at
"Clausing 5914 - Test Report Requirements". And so on. That lathe
generated a lot of stories.

Joe Gwinn

Tim Wescott wrote in
news
Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound up,
wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.


While these may well be idiotic ideas, I'll offer them anyway.

1. Have you considered simply using a hacksaw while the part is spinning?

2. (A variant) Have you considered soldering the spine of a piece of
hacksaw blade to a tool blank?

On Fri, 26 Dec 2008 13:26:05 -0800, Tim Wescott
wrote:

Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound up,
wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.


I've actually made those things before.... for guys racing model
boats!

Anyway, what points to the problem is the chatter. How or with what
did it "bind?"

What is loose? How big a lathe? How are you holding the part? Was the
cutter properly lined up with the axis of the lathe? Proper clearances
all around? Was the carriage locked? How much lost motion is in the
compound rest (or was it locked)? What sort of tool holder? How close
to center was the tool? Lotsa questions!

Unless this is a really tiny lathe you really shouldn't have any
chatter with a .050 wide grooving tool.
--

Forté Agent 5.00 Build 1171

"When a work lifts your spirits and inspires bold and
noble thoughts in you, do not look for any other standard
to judge by: the work is good, the product of a master
craftsman." - Jean de la Bruyere (1645-1696)

Homepage
http://pamandgene.tranquilrefuge.net...shop/index.htm
-----------------
www.Newsgroup-Binaries.com - *Completion*Retention*Speed*
Access your favorite newsgroups from home or on the road
-----------------

"Gene" wrote in message
...
On Fri, 26 Dec 2008 13:26:05 -0800, Tim Wescott
wrote:

Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound up,
wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.


I've actually made those things before.... for guys racing model
boats!

Anyway, what points to the problem is the chatter. How or with what
did it "bind?"

What is loose? How big a lathe? How are you holding the part? Was the
cutter properly lined up with the axis of the lathe? Proper clearances
all around? Was the carriage locked? How much lost motion is in the
compound rest (or was it locked)? What sort of tool holder? How close
to center was the tool? Lotsa questions!

Unless this is a really tiny lathe you really shouldn't have any
chatter with a .050 wide grooving tool.
--

Forté Agent 5.00 Build 1171

"When a work lifts your spirits and inspires bold and
noble thoughts in you, do not look for any other standard
to judge by: the work is good, the product of a master
craftsman." - Jean de la Bruyere (1645-1696)

Homepage
http://pamandgene.tranquilrefuge.net...shop/index.htm
-----------------
www.Newsgroup-Binaries.com - *Completion*Retention*Speed*
Access your favorite newsgroups from home or on the road
-----------------

Once you get the chatter taken care of, you might be interested in this tip
from people who make small engines with narrow fins: Make a disk that just
fits between an adjacent pair of fins, and split it so you can place it in
the last slot you cut. Tape should hold it in place.

When you're cutting fins with a slotting tool the previously-cut fin can get
pushed out of shape by side force from the cutting tool. The filler should
prevent the problem.

I have tried this but, frankly, I don't know if I would have had a problem
without it, because I used the trick on the first cylinder I tried cutting.
That experiment had some other problems but chatter wasn't among them. I
haven't had a lot of chatter problems with cutoff or slotting. 'Lucky, I
guess.

--
Ed Huntress

On Fri, 26 Dec 2008 13:26:05 -0800, Tim Wescott wrote:



I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound up,
wrenched the cylinder out of the chuck, and broke.


Shouldn't be a major problem. Make sure you have side relief on the tool. 2
degrees per side would be ideal, but one will do if it's consistent. That
gives the back of the tool being 10 mils thinner than the front for 1 degree.
Make sure the edge is perfectly square and sharp, with no more than 2 degrees
of front relief (that'll help to stop it digging in). No top rake at all. you
want a tool that can be fed very controllably and won't tend to dig in.

When mounting the tool, use a DTI or dial test gauge on the side to ensure
that the tool is straight. The change in reading as the cross slide is moved
should be the same for both sides of the tool.

Lock the saddle, nip up the top slide gib screws and ensure that the cross
slide gib screws aren't slack.

If the cylinder has already been bored, then mount it against a shoulder on an
arbor turned to a firm fit, drilled and tapped for a clamping screw and washer
and then not removed from the chuck. Turn the clamping washer before doing the
arbor!


You should be able to turn at normal turning speeds, just keep the feed under
control if the tool post/top slide are a bit flexible.


Mark Rand
RTFM

Tim Wescott wrote:

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.


Did you grind the nose so it isn't trying to push left or right?

Diamond hone it sharp. On center. Positive rake.

Minimize the stick out as in no extra tool protruding from holder.

Not sure this is a good idea but can you grind a valley in top of parting tool to fold
your chip for clearance? I'd like to hear comments on that idea if it is good or bad.

Slitting blade, arbor, rotary table and mill also comes to mind.

Wes

Tim Wescott wrote:
Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound up,
wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.

keeping all overhangs to a minimum, buth tool and
workpiece, are good things to do. Possibly going
to an even narrower grooving tool, and alternating
taking a little off each side of the groove would
work better.

You probably need to understand what was going
wrong. Was the work too flexible, or the tool?
It depends to some extent on the rigidity of the
lathe, too. When I used Atlas/Craftsman lathes,
any cutoff job was a nerve-rattling exercise, and
bind-ups were VERY common. Now that I have a 3500
Lb Sheldon 15" lathe, I rarely have any problem
with cutoff or grooving operations that would have
been unthinkable on the Atlas. So, the total
rigidity of the machine must be part of the
difference.

Jon

Tim Wescott wrote:

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November?

Oh, one other thing for parting or grooving tools.
Grind a slight groove in the top of the tool, so
that the chip is forced to curl inward. What you
need is the left and right edges of the tool to be
higher than the middle, so there is a little bit
of a valley coming out towards you. This curling
inwards makes the chip narrower than the groove,
eliminating the binding in the groove. When you
get it right, the chips come off rolled up, and
there is a clear barrel-shape to them.

Jon

"Jon Elson" wrote in message
...
Tim Wescott wrote:

Any pointers, or should I just make a new tool, do the same stupid thing,
and see if the laws of physics have changed since November?

Oh, one other thing for parting or grooving tools. Grind a slight groove
in the top of the tool, so that the chip is forced to curl inward. What
you need is the left and right edges of the tool to be higher than the
middle, so there is a little bit of a valley coming out towards you. This
curling inwards makes the chip narrower than the groove, eliminating the
binding in the groove. When you get it right, the chips come off rolled
up, and there is a clear barrel-shape to them.

Jon

This is the way that commercial cutoff inserts are made, and it works fine
with those wider cutoff/grooving inserts. I haven't had any luck trying to
do it with very narrow ones because the chips just jam against each other.

Have you tried it with narrow grooving tools? Tim says this one is only
0.050" wide.

--
Ed Huntress

"Tim Wescott" wrote in message
news
Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound up,
wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can finesse
the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid thing,
and see if the laws of physics have changed since November? I _did_ make
sure that things were as rigid as possible, with the exception that I
probably had the cylinder sticking too far out of the chuck, out of
paranoia about hitting the jaws with the tool holder.

Sounds like your tool isn't properly ground, Tim.

Did you provide side relief, both top to bottom and front to back? If the
tool touches anywhere but at the tip, the point of the cut, you can expect
terrible results.

Did you provide a small amount of positive rake? It often helps the cut,
and provides additional relief when the tool is properly ground.

Did you try parting dry? That's a mistake unless you're machining 2024, and
even then it's not the smartest thing you can do.

As for creating the fins, you'd be well served to use a long travel
indicator to index the cuts. Measure the width of the tool, then determine
how thick you want the fins to be. Make that offset after each one is
machined.

if your tool cuts well, you should end up with a clean cut on both faces of
the fin. If you find it doesn't, you might explore a tool that is slightly
undersized, then face each side after you've taken the groove to depth.

Unless you have a pygmy lathe (not trying to be rude), you shouldn't have
any problems with this little project. The grind of the tool is
everything.

Harold

On Sat, 27 Dec 2008 05:04:29 +0000, Harold and Susan Vordos wrote:

"Tim Wescott" wrote in message
news
Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound
up, wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.

Sounds like your tool isn't properly ground, Tim.

Did you provide side relief, both top to bottom and front to back? If
the tool touches anywhere but at the tip, the point of the cut, you can
expect terrible results.

Did you provide a small amount of positive rake? It often helps the
cut, and provides additional relief when the tool is properly ground.

Did you try parting dry? That's a mistake unless you're machining 2024,
and even then it's not the smartest thing you can do.

As for creating the fins, you'd be well served to use a long travel
indicator to index the cuts. Measure the width of the tool, then
determine how thick you want the fins to be. Make that offset after
each one is machined.

if your tool cuts well, you should end up with a clean cut on both faces
of the fin. If you find it doesn't, you might explore a tool that is
slightly undersized, then face each side after you've taken the groove
to depth.

Unless you have a pygmy lathe (not trying to be rude), you shouldn't
have any problems with this little project. The grind of the tool is
everything.

Harold

Having read all the posts, I suspect that my problems are, in order:

* I let the tool get dull -- it worked for some cuts, then
got worse and worse and ...
* Not enough positive rake, possibly exacerbating the sharpness.
I knew this, but I was lazy.
* Heat. Coolant would be a real pain, but I can try flooding it
with lubricant, and going slow.

There may be other problems, but when next I get the chance I'll go
remake the tool and give it a try.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

"Tim Wescott" wrote in message
...
On Sat, 27 Dec 2008 05:04:29 +0000, Harold and Susan Vordos wrote:
snip---

Having read all the posts, I suspect that my problems are, in order:

* I let the tool get dull -- it worked for some cuts, then
got worse and worse and ...

That is likely a function of surface speed. The tool should have held up for
the amount of cutting involved. Try slowing down ever so slightly. If the
chips came off anything but a pale yellow or silver metal color, you ran too
fast.

* Not enough positive rake, possibly exacerbating the sharpness.
I knew this, but I was lazy.

As you increase rake, the tool will tend to peel the metal instead of push
it off. That lowers cutting pressure and often results in a cooler
cut----although with the reduced mass at the point of cut, the result of the
angle of rake, the tool may heat just as quickly as it did previously.
Pressure will be lower, however, and that's a good thing.

* Heat. Coolant would be a real pain, but I can try flooding it
with lubricant, and going slow.

Cooling is important, but not nearly as important as lubrication. It's
virtually impossible to part dry---although a few metals will cooperate.
Leaded steels and brass tend to part dry fairly well, as does 2024 aluminum,
but you're never sorry for adding lubrication. If it doesn't do anything
else, it helps chip evacuation, although there's far more involved. You
limit or eliminate chip welding, and cut cutting pressure in ways that are
hard to believe. You need not flood the cut----an acid brush (don't use a
paint brush---it doesn't hold a supply of oil the way an acid brush does)
held in the groove while cutting will make a remarkable improvement, plus
the reduced friction will yield less heat. Overall, you'll see an
improvement you can't believe. Give it a go. You'll be pleasantly
surprised. If you don't have any of the 1,1,1, trichloroethane, try sulfur
based cutting oil. It stinks, but it does a decent job.

One more consideration. The material you're using can make a huge
difference. If you're using mild steel (C1018 up through any of the 1020
materials, hot or cold rolled), you can expect grief. You might consider
making the cylinder out of Stressproof (1144). It machines beautifully,
especially with HSS. It also has great properties.

There may be other problems, but when next I get the chance I'll go
remake the tool and give it a try.

Be certain to have relief properly ground.

It would have been interesting to hear about the lathe you're using. Did
you make mention and I missed it?

Small machines are not the best scenario for parting, although with a narrow
tool you should achieve excellent results. If you find you're having
trouble, use a narrower tool, plunge the centerline of each groove, then,
using a long travel indicator, step over and face each side. With a sharp
tool you should be able to do so without problems, assuming the fins are
reasonably thick.

How about a report on the project when you're finished? I'd be interested
in hearing the outcome. Sounds like a good one to pursue.

Harold

On Sat, 27 Dec 2008 08:55:14 +0000, Harold and Susan Vordos wrote:

"Tim Wescott" wrote in message
...
On Sat, 27 Dec 2008 05:04:29 +0000, Harold and Susan Vordos wrote:
snip---

Having read all the posts, I suspect that my problems are, in order:

* I let the tool get dull -- it worked for some cuts, then
got worse and worse and ...

That is likely a function of surface speed. The tool should have held up
for the amount of cutting involved. Try slowing down ever so slightly.
If the chips came off anything but a pale yellow or silver metal color,
you ran too fast.

* Not enough positive rake, possibly exacerbating the sharpness.
I knew this, but I was lazy.

As you increase rake, the tool will tend to peel the metal instead of
push it off. That lowers cutting pressure and often results in a cooler
cut----although with the reduced mass at the point of cut, the result of
the angle of rake, the tool may heat just as quickly as it did
previously. Pressure will be lower, however, and that's a good thing.

* Heat. Coolant would be a real pain, but I can try flooding it
with lubricant, and going slow.

Cooling is important, but not nearly as important as lubrication. It's
virtually impossible to part dry---although a few metals will cooperate.
Leaded steels and brass tend to part dry fairly well, as does 2024
aluminum, but you're never sorry for adding lubrication. If it doesn't
do anything else, it helps chip evacuation, although there's far more
involved. You limit or eliminate chip welding, and cut cutting pressure
in ways that are hard to believe. You need not flood the cut----an
acid brush (don't use a paint brush---it doesn't hold a supply of oil
the way an acid brush does) held in the groove while cutting will make a
remarkable improvement, plus the reduced friction will yield less heat.
Overall, you'll see an improvement you can't believe. Give it a go.
You'll be pleasantly surprised. If you don't have any of the 1,1,1,
trichloroethane, try sulfur based cutting oil. It stinks, but it does a
decent job.

One more consideration. The material you're using can make a huge
difference. If you're using mild steel (C1018 up through any of the 1020
materials, hot or cold rolled), you can expect grief. You might
consider making the cylinder out of Stressproof (1144). It machines
beautifully, especially with HSS. It also has great properties.

There may be other problems, but when next I get the chance I'll go
remake the tool and give it a try.

Be certain to have relief properly ground.

It would have been interesting to hear about the lathe you're using.
Did you make mention and I missed it?

Small machines are not the best scenario for parting, although with a
narrow tool you should achieve excellent results. If you find you're
having trouble, use a narrower tool, plunge the centerline of each
groove, then, using a long travel indicator, step over and face each
side. With a sharp tool you should be able to do so without problems,
assuming the fins are reasonably thick.

How about a report on the project when you're finished? I'd be
interested in hearing the outcome. Sounds like a good one to pursue.

Harold

Sorry -- it's a Smithy "3" in one (actually 2 + excuse in one, but the
excuse is the milling section; the lathe seems to be pretty good). Other
than the compound, which seems to have some taper in the dovetail, I can
get good control of the rigidity by snugging down the jib screws.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

Tim, you can check the rigidity of the compound/top slide to see if it is
firmly supporting a cutoff/parting/grooving tool with overhang, particularly
since the compound is located near the edge of the cross slide on a Smithy.

By placing a length of stock or a bar-shaped tool about 12 inches long in
the toolholder (or turret), and applying light to moderate vertical finger
pressure at the end of the bar, any movement that is seen in the compound
would be an indication that the cutting tool has vertical movement onder the
load of cutting.
Besides the cutting tool being able to dip down while cutting, any sideways
twist will very likely break a small cutting tool of that size.

If you're compound is set parallel to the spindle axis, you may want to try
resetting it to be perpendicular to the spindle axis, or somewhere
in-between.

I realize that supporting such a short/small part with the tailstock center
on a Smithy is probably not possible. Attempting to use the extension for
the tailstock ram will probably not be worthwhile, as the overhang is too
great for the area of the base of the tailstock.

I agree with the suggestions of placing the cylinder on an expanding arbor,
this would be a great improvement over trying to chuck a hollow part.

If you have a big endmill holder (and a drawbar) that fits the spindle taper
MT4, it should be a good substitute for using a chuck.
By turning a snug-fitting stem to put in the big endmill holder, a stub (the
diameter that would hold your cylinder) could be turned for it to mount on.
If you wanted to go further, you could drill the stub, tap for a 1/8" pipe
plug or set screw, then slit the stub so it would expand inside your
cylindrical part.
Otherwise an end screw and a washer would probably suffice (with the motor
running in the forward direction).

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Tim Wescott" wrote in message
...
On Sat, 27 Dec 2008 08:55:14 +0000, Harold and Susan Vordos wrote:

That is likely a function of surface speed. The tool should have held up
for the amount of cutting involved. Try slowing down ever so slightly.
If the chips came off anything but a pale yellow or silver metal color,
you ran too fast.

As you increase rake, the tool will tend to peel the metal instead of
push it off. That lowers cutting pressure and often results in a cooler
cut----although with the reduced mass at the point of cut, the result of
the angle of rake, the tool may heat just as quickly as it did
previously. Pressure will be lower, however, and that's a good thing.

Cooling is important, but not nearly as important as lubrication. It's
virtually impossible to part dry---although a few metals will cooperate.
Leaded steels and brass tend to part dry fairly well, as does 2024
aluminum, but you're never sorry for adding lubrication. If it doesn't
do anything else, it helps chip evacuation, although there's far more
involved. You limit or eliminate chip welding, and cut cutting pressure
in ways that are hard to believe. You need not flood the cut----an
acid brush (don't use a paint brush---it doesn't hold a supply of oil
the way an acid brush does) held in the groove while cutting will make a
remarkable improvement, plus the reduced friction will yield less heat.
Overall, you'll see an improvement you can't believe. Give it a go.
You'll be pleasantly surprised. If you don't have any of the 1,1,1,
trichloroethane, try sulfur based cutting oil. It stinks, but it does a
decent job.

One more consideration. The material you're using can make a huge
difference. If you're using mild steel (C1018 up through any of the 1020
materials, hot or cold rolled), you can expect grief. You might
consider making the cylinder out of Stressproof (1144). It machines
beautifully, especially with HSS. It also has great properties.

Be certain to have relief properly ground.

It would have been interesting to hear about the lathe you're using.
Did you make mention and I missed it?

Small machines are not the best scenario for parting, although with a
narrow tool you should achieve excellent results. If you find you're
having trouble, use a narrower tool, plunge the centerline of each
groove, then, using a long travel indicator, step over and face each
side. With a sharp tool you should be able to do so without problems,
assuming the fins are reasonably thick.

How about a report on the project when you're finished? I'd be
interested in hearing the outcome. Sounds like a good one to pursue.

Harold

Sorry -- it's a Smithy "3" in one (actually 2 + excuse in one, but the
excuse is the milling section; the lathe seems to be pretty good). Other
than the compound, which seems to have some taper in the dovetail, I can
get good control of the rigidity by snugging down the jib screws.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

I agree with all of your recommendations, Jim. And it's reasonable that if
"I do this" works well, then that's definitely the way to go.
Some of the other folks with different machines will need to adopt their own
"I do this" procedures for whatever works best for them.

The parting tool I've been using is 1/8" wide x 1/2" high HSS, the tapered
cross section type. The tool holder I use also holds the blade at an
(upward) angle, but I haven't measured it. I was concerned that a chip
breaker ground into the tip would be too much top/back relief, but it works
well.
The chip breaker might not be the ideal tool profile for power cross feed,
but it's definitely been beneficial for manual cross feed.
The chip breaker tip has worked well for all of my mild steel and aluminum
parting operations up to about 1.5" diameter, and smaller diameters of
stainless steel (just haven't had any need to part/cutoff larger SS yet).
The very slight front relief made a dramatic improvement, completely
eliminating any digging/grabbing in the workpiece. Of course variable
spindle speed makes it easy to find a good relationship between spindle
speed and manual cross feed rate.

For larger diameters, I use the band saw to cut sections, since the cutoff
blade would be extended too far to complete larger diameters, unless the
larger diameter would have an axial hole, then the parting/cutoff blade
would probably work well.
The problem with large diameter stock is that for parting, the tailstock
center should never be use to complete the parting, so the section of large
round stock would need to be short so that the parting groove would be near
the lathe chuck.

Nearly any parting operation will go smoother if the workpiece is to have an
axial hole in it, and the hole is drilled before the parting/cutoff
operation.

The tapered type parting/cutoff blades provide good side clearances, but
it's important to mount the blade as perfectly vertical as it can be. Some
blade holders aren't machined properly to set the blade in the vertical
position, so the operator needs to be aware of this.

I haven't used the T-shaped parting blades, but I've read good comments
about their performance.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Jim Wilkins" wrote in message
...
On Dec 26, 4:48 pm, "Wild_Bill" wrote:
Grooving and parting off require a rigid setup, which you may already
know,
Tim.
Snug everything down except the cross feed, and even the cross feed if
there
is much backlash in the feed threads.

Including the carriage lock.

My Multifix parting holder and Enco bit work pretty well most of the
time. I don't claim to understand exactly why but I'll describe it for
you. If anyone knows better, listen to them instead. I'm almost
totally self-taught and some of this may be simply adapting to the
quirks of my lathe. "I do this..." is my code for YMMV.

The holder slopes the bit 4 degrees for top rake. The front rake is
presently 16 degrees on the bit, or 12 WRT the work. That may be
excessive. I think the minimum is 5.

I hollow-grind the end so a hand-held stone touches only the cutting
edge and the lower heel. With heel contact to guide it, the stone
doesn't rock vertically when I clean up the edge every few minutes in
SS, or weekly in Al. It rounds the end laterally but that doesn't seem
to matter.

The bit protrudes about 9/16" to cut off up to 1" rod in 5C collets.
It definitely works better at half that.

I grind square across, so the bit leaves a tit on the cut-off part.
Grinding the end at a small angle is said to cure this, but with 9/16"
of protrusion the 0.062" x 1/2" bit flexes too much from the side
thrust.

I use a needle oil bottle to slowly feed oil into the slot. The tip
usually rides along the bottom. This is tedious and boring but if I
stop or try brushing the bit often jams within a minute. The belt is
loose enough that I only have to push the cone pulley backwards to
free the bit, back out, then feed very slowly until the ticking stops.

For a repetitive job I soon get the feed figured out and use the auto
crossfeed.

I tighten the toolpost bolt with the cutoff holder pressed against the
end of the spindle or the collet adapter.

Home Depot pipe threading oil works for me on SS, drill rod and
aluminum.

See/hear chatter, slow down a step. I've only used the backgear when
parting 3" steel, a job I had to complete with the bandsaw.

I make delicate things on the end of solid rod stock held in a collet
and often with tailstock support as well.
How deep are the slots?

Jim Wilkins




"Tim Wescott" wrote in message
news
Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound up,
wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can finesse
the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid thing,
and see if the laws of physics have changed since November? I _did_ make
sure that things were as rigid as possible, with the exception that I
probably had the cylinder sticking too far out of the chuck, out of
paranoia about hitting the jaws with the tool holder.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Tim Wescott wrote:
Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound up,
wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.


I would guess that you ground the parting tool from 1/4 square? If so
your asking a lot for the tool to plunge .3" deep even if ground very well.

For a one off groove I'll use the compound set parallel to the ways and
feed 1x to 1.5x the tool width then pull out, move the compound over and
plunge again, etc.

Obviously, the tool must be ground narrower than the finished groove for
you to do it this way.

Most folks part with the tool on or slightly below center with somewhere
between "0" up to half the usual rake used for a given material. Side
clearance is crucial for deep plunging, but less so for "pecking".

You've got lots of time, the part is precious.

Matt

On Sat, 27 Dec 2008 09:16:24 -0600, matthew maguire wrote:

Tim Wescott wrote:
Problem: A Cox 15 replacement cylinder, than needs fins.

I machined an itty bitty cutoff tool, about 50 mils wide and 300 mils
deep. It chattered. I gritted my teeth and kept feeding. It bound
up, wrenched the cylinder out of the chuck, and broke.

Fortunately the part looks to be recoverable, assuming that I can
finesse the spot where the chunks of tool dug into the steel.

But I still need to turn in those damn grooves between the fins.

Any pointers, or should I just make a new tool, do the same stupid
thing, and see if the laws of physics have changed since November? I
_did_ make sure that things were as rigid as possible, with the
exception that I probably had the cylinder sticking too far out of the
chuck, out of paranoia about hitting the jaws with the tool holder.


I would guess that you ground the parting tool from 1/4 square? If so
your asking a lot for the tool to plunge .3" deep even if ground very
well.

For a one off groove I'll use the compound set parallel to the ways and
feed 1x to 1.5x the tool width then pull out, move the compound over and
plunge again, etc.

Obviously, the tool must be ground narrower than the finished groove for
you to do it this way.

Most folks part with the tool on or slightly below center with somewhere
between "0" up to half the usual rake used for a given material. Side
clearance is crucial for deep plunging, but less so for "pecking".

You've got lots of time,

Yes.

the part is precious.

Well...

Actually, at this point the part has been through the wars. It's still
clinging to "finish it and try it out but don't let anyone see it" -- any
more stuff-ups and it'll attain the status of "the one I screwed up on so
I could get the next one right".

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

On Sat, 27 Dec 2008 12:27:44 -0600, Tim Wescott wrote:


Actually, at this point the part has been through the wars. It's still
clinging to "finish it and try it out but don't let anyone see it" -- any
more stuff-ups and it'll attain the status of "the one I screwed up on so
I could get the next one right".

Unless you are doing it for money, there's nothing particularly wrong with
having to make the odd, difficult, part a few times as a "learning"
experience.

At least, that's what I tell myself :-)


Mark Rand
RTFM

On Sun, 28 Dec 2008 00:08:01 +0000, Mark Rand wrote:

On Sat, 27 Dec 2008 12:27:44 -0600, Tim Wescott
wrote:


Actually, at this point the part has been through the wars. It's still
clinging to "finish it and try it out but don't let anyone see it" --
any more stuff-ups and it'll attain the status of "the one I screwed up
on so I could get the next one right".

Unless you are doing it for money, there's nothing particularly wrong
with having to make the odd, difficult, part a few times as a "learning"
experience.

At least, that's what I tell myself :-)

Well, yes. But I take that to mean that I should continue trying to make
the part until it is _completely_ hopeless before I start over again.

After all, if everything I did looked really good, people would think I'm
a competent machinist. I don't want them to be deceived...

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html