For class I'm turning an aluminum flywheel. 3" diameter. The steps
a face the sides, drill & ream the center, press onto a mandrel, turn
the outside and sides. Anyway, after pressing it onto the mandrel (yes,
I cleaned out the cutting oil) I've found that I have to go very slowly
or the cutting tool will grab the wheel and spin it on the mandrel.
What are some good ways to deal with this problem? I already crammed
it as far onto the mandrel as I'm comfortable with. I'm tempted to just
loctite the damn thing.

--
B.B. --I am not a goat! thegoat4 at airmail dot net
http://web2.airmail.net/thegoat4/

"B.B." u wrote in message
news
For class I'm turning an aluminum flywheel. 3" diameter. The steps
a face the sides, drill & ream the center, press onto a mandrel, turn
the outside and sides. Anyway, after pressing it onto the mandrel (yes,
I cleaned out the cutting oil) I've found that I have to go very slowly
or the cutting tool will grab the wheel and spin it on the mandrel.
What are some good ways to deal with this problem? I already crammed
it as far onto the mandrel as I'm comfortable with. I'm tempted to just
loctite the damn thing.



Wow!

Without seeing it, it's hard to second guess the problem. Can I assume the
mandrel is ½?" Pressed with an arbor press? Tapped in with a hammer? Cast
aluminum, or bar stock?

That's not much to drive a large diameter cut. A couple things can help.
Make certain that your cutting tool is sharp, with a slight radius (1/64"
max) stoned on the tip so it cuts smoothly, but not too large, so you
increase surface area in contact with the cut. That can lead to chatter, and
increases cutting pressure, often overwhelming the friction fit of the
mandrel. A little positive rake will lower cutting resistance, but too
much will encourage hogging or chatter, so you have to walk a delicate line.
Take a lighter cut and finer feed. Do what it takes to lower cutting
pressure, but don't allow chatter to start. Once you get it, it can be
difficult to eliminate. Higher speeds encourage chatter, but improve
machining.

Harold

"B.B." u wrote in message
news
For class I'm turning an aluminum flywheel. 3" diameter. The steps
a face the sides, drill & ream the center, press onto a mandrel, turn
the outside and sides. Anyway, after pressing it onto the mandrel (yes,
I cleaned out the cutting oil) I've found that I have to go very slowly
or the cutting tool will grab the wheel and spin it on the mandrel.
What are some good ways to deal with this problem? I already crammed
it as far onto the mandrel as I'm comfortable with. I'm tempted to just
loctite the damn thing.


Heat it, then quickly press it on--to remove, heat it up again.......~350
degrees F. should do the trick....remember, aluminum expands at a greater
rate than steel....

Oh, and take lighter cuts, use a sharp tool, etc....cause if it heats
up........

--

SVL

On Wed, 02 Mar 2005 22:25:40 -0600, "B.B."
u wrote:

For class I'm turning an aluminum flywheel. 3" diameter. The steps
a face the sides, drill & ream the center, press onto a mandrel, turn
the outside and sides. Anyway, after pressing it onto the mandrel (yes,
I cleaned out the cutting oil) I've found that I have to go very slowly
or the cutting tool will grab the wheel and spin it on the mandrel.
What are some good ways to deal with this problem? I already crammed
it as far onto the mandrel as I'm comfortable with. I'm tempted to just
loctite the damn thing.

Superglue works quite well as long as you dont have any tool chatter.
So does regular fingernail polish.

I make my own mandrels by turning a rod to diameter, drilling and
tapping the end, then slitting with a hacksaw or slitting saw. Slip
over the workpiece, then installing a socket head cap screw in the
tapped hole to expand as needed.

Best if done in a collet of course. but works fine in a three jaw if
you dont remove it during any of the process.

Cheap and easy to make, grabs well.

Gunner


Lathe Dementia. Recognized as one of the major sub-strains of the
all-consuming virus, Packratitis. Usual symptoms easily recognized
and normally is contracted for life. Can be very contagious.
michael

"Gunner" wrote in message
news
On Wed, 02 Mar 2005 22:25:40 -0600, "B.B."
u wrote:

For class I'm turning an aluminum flywheel. 3" diameter. The steps
a face the sides, drill & ream the center, press onto a mandrel, turn
the outside and sides. Anyway, after pressing it onto the mandrel (yes,
I cleaned out the cutting oil) I've found that I have to go very slowly
or the cutting tool will grab the wheel and spin it on the mandrel.
What are some good ways to deal with this problem? I already crammed
it as far onto the mandrel as I'm comfortable with. I'm tempted to just
loctite the damn thing.

Superglue works quite well as long as you dont have any tool chatter.
So does regular fingernail polish.

I make my own mandrels by turning a rod to diameter, drilling and
tapping the end, then slitting with a hacksaw or slitting saw. Slip
over the workpiece, then installing a socket head cap screw in the
tapped hole to expand as needed.

Best if done in a collet of course. but works fine in a three jaw if
you dont remove it during any of the process.

Cheap and easy to make, grabs well.

Gunner

Works real well with a pipe plug, too. It's a good idea to try to make
your cuts at 90°, so when you expand the mandrel it does so uniformly and
retains concentricity. Rough turn, drill, tap, split, deburr the threads
with your pipe tap, then finish turn with the pipe plug tightened ever so
slightly. You can do surprisingly precise work with a mandrel so made.

Harold

"Harold and Susan Vordos" wrote in message
...

"Gunner" wrote in message
news
On Wed, 02 Mar 2005 22:25:40 -0600, "B.B."
u wrote:

For class I'm turning an aluminum flywheel. 3" diameter. The steps
a face the sides, drill & ream the center, press onto a mandrel,
turn
the outside and sides. Anyway, after pressing it onto the mandrel
(yes,
I cleaned out the cutting oil) I've found that I have to go very slowly
or the cutting tool will grab the wheel and spin it on the mandrel.
What are some good ways to deal with this problem? I already
crammed
it as far onto the mandrel as I'm comfortable with. I'm tempted to
just
loctite the damn thing.

Superglue works quite well as long as you dont have any tool chatter.
So does regular fingernail polish.

I make my own mandrels by turning a rod to diameter, drilling and
tapping the end, then slitting with a hacksaw or slitting saw. Slip
over the workpiece, then installing a socket head cap screw in the
tapped hole to expand as needed.

Best if done in a collet of course. but works fine in a three jaw if
you dont remove it during any of the process.

Cheap and easy to make, grabs well.

Gunner

Works real well with a pipe plug, too. It's a good idea to try to make
your cuts at 90°, so when you expand the mandrel it does so uniformly and
retains concentricity. Rough turn, drill, tap, split, deburr the threads
with your pipe tap, then finish turn with the pipe plug tightened ever so
slightly. You can do surprisingly precise work with a mandrel so made.


The "splitting" part is what becomes the problem here--it's best done in
this case with just a plain ole hacksaw....with the mandrel still firmly
chucked in the lathe....

From start to finish, once you chuck your mandrel blank you should forget
that you even *own* a chuck key--throw the darned thing out the bay door and
retrieve it later......cause if you unchuck the work and have to re-set it
then all bets are off....

===

Never forget that turning or milling, makes no differance--your primary axis
is always gonna defined by your spindle bearings, and all other planes are
defined from that referance.

--

SVL

In article ,
"PrecisionMachinisT" wrote:

The "splitting" part is what becomes the problem here--it's best done in
this case with just a plain ole hacksaw....with the mandrel still firmly
chucked in the lathe....

From start to finish, once you chuck your mandrel blank you should forget
that you even *own* a chuck key--throw the darned thing out the bay door and
retrieve it later......cause if you unchuck the work and have to re-set it
then all bets are off....

Nothing says the chuck has to remain on the lathe, just the mandrel
stays in the chuck.

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/

"Nick Hull" wrote in message
...
In article ,
"PrecisionMachinisT" wrote:

The "splitting" part is what becomes the problem here--it's best done
in
this case with just a plain ole hacksaw....with the mandrel still firmly
chucked in the lathe....

From start to finish, once you chuck your mandrel blank you should
forget
that you even *own* a chuck key--throw the darned thing out the bay door
and
retrieve it later......cause if you unchuck the work and have to re-set
it
then all bets are off....

Nothing says the chuck has to remain on the lathe, just the mandrel
stays in the chuck.


While most mounts are pretty darned accurate, I wouldnt bet on it without
having some familarity with the actual lathe thats being used.

--

SVL

On Thu, 3 Mar 2005 00:56:06 -0800, "Harold and Susan Vordos"
wrote:


"Gunner" wrote in message
news
On Wed, 02 Mar 2005 22:25:40 -0600, "B.B."
u wrote:

For class I'm turning an aluminum flywheel. 3" diameter. The steps
a face the sides, drill & ream the center, press onto a mandrel, turn
the outside and sides. Anyway, after pressing it onto the mandrel (yes,
I cleaned out the cutting oil) I've found that I have to go very slowly
or the cutting tool will grab the wheel and spin it on the mandrel.
What are some good ways to deal with this problem? I already crammed
it as far onto the mandrel as I'm comfortable with. I'm tempted to just
loctite the damn thing.

Superglue works quite well as long as you dont have any tool chatter.
So does regular fingernail polish.

I make my own mandrels by turning a rod to diameter, drilling and
tapping the end, then slitting with a hacksaw or slitting saw. Slip
over the workpiece, then installing a socket head cap screw in the
tapped hole to expand as needed.

Best if done in a collet of course. but works fine in a three jaw if
you dont remove it during any of the process.

Cheap and easy to make, grabs well.

Gunner

Works real well with a pipe plug, too. It's a good idea to try to make
your cuts at 90°, so when you expand the mandrel it does so uniformly and
retains concentricity. Rough turn, drill, tap, split, deburr the threads
with your pipe tap, then finish turn with the pipe plug tightened ever so
slightly. You can do surprisingly precise work with a mandrel so made.

Harold

Ayup. Mine are threaded for 1/8" pipe plugs..but most folks dont have
em, so suggested the standard bolt. The threaded and Tapered pipe
thread is the best way to go.

I slit mine on the Mastermill with slitting saws and the mandrels held
in a 5C indexer.

Sometimes I have to think hard on how to do things when the other guy
may not have Stuff.

Gunner


Lathe Dementia. Recognized as one of the major sub-strains of the
all-consuming virus, Packratitis. Usual symptoms easily recognized
and normally is contracted for life. Can be very contagious.
michael

In article , B.B.
says...

For class I'm turning an aluminum flywheel. 3" diameter. The steps
a face the sides, drill & ream the center, press onto a mandrel, turn
the outside and sides. Anyway, after pressing it onto the mandrel (yes,
I cleaned out the cutting oil) I've found that I have to go very slowly
or the cutting tool will grab the wheel and spin it on the mandrel.

Change the order in which you perform the operations.

1) clamp via the OD on the rough blank, and turn one side and the
part of the OD that is extending out from the chuck jaws, but leave
20 thou or so for cleanup later on the OD.

2) in the same setup, rough drill the bore.

3) Flip it around in the chuck, so that the jaws are now grabbing
on the finished OD from the previous step. Profile the second side
and the OD again to a 20 over size. Finish bore and ream the
ID dimension. (when you seat the part for this step, be sure
it is bottomed in the jaws and that there are no chips under
it)

4) use a stub mandrel in the headstock, with the stub turned
in place - at a diameter one thou under the bore size.
Also put a pusher block in the tailstock, a live center makes
this run easily.

Then your flywheel goes over the stub on the mandrel (which picks
up the finished bore) and the pusher block forces the part up against
the face of the mandrel, which now drives the part for taking the
final OD cut on the part.

You can glue some sandpaper on the mandrel face (which should be
only slightly smaller then the part's diameter) to assist with
driving it.

The benefit of this approach is:

The OD of the part is dead concentric with the bore, which is
the most important issue.

The OD is turned with the part held rigidly between two large
driver blocks - so there is much less chance for ringing or
chatter.

You can take as big a cut on the OD as you want because it
*will* drive.

How do I know all this? Because I spent a few years making
crane sheaves out of nylon. This is the way it was done, and
the OD cuts were often done with form tools, which require
large cutting forces and are very prone to chatter becaue of
the amount of tool engaged in the workpiece.

Make a stub mandrel and a pusher block, you could turn 20 flywheels
from blanks in a half hour.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

hold the mandrel short so the flywheel is touching the jaws and center
drill a piece of 1 x 1 x 4 in the center of the length and use the
tailstock to press the flywheel up against the jaws .......

or

just turn it backwards and turn your tool upside down, so the nut will
tend to tighten instead of loosen

In article
,
"B.B." u wrote:

For class I'm turning an aluminum flywheel. 3" diameter. The steps
a face the sides, drill & ream the center, press onto a mandrel, turn
the outside and sides. Anyway, after pressing it onto the mandrel (yes,
I cleaned out the cutting oil) I've found that I have to go very slowly
or the cutting tool will grab the wheel and spin it on the mandrel.
What are some good ways to deal with this problem? I already crammed
it as far onto the mandrel as I'm comfortable with. I'm tempted to just
loctite the damn thing.

Replying to all:

I like the method jim described since it's sturdy, but I can't use it
since I've already done just about all of it except for turning the
grooves in the sides. Of course, if I ruin it.... However, I believe
we're doing this part mostly for the sake of turning something between
centers as part of the class. I'm nearly done with the assigned project
and have a half a semester to go for whatever, so I can probably try
this at some point.
Harold, When you wrote "Can I assume the mandrel is ½?" that last
character came out as Pi on my screen, and I have no idea what you meant
by it. But, bar stock, pressed the mandrel in with an arbor press.
We're using general-purpose indexable carbide tools on all of the
lathes, but I have a fresh bit of tool steel and I'll see about making
my own tool to play with. I did find (counter-intuitively) that running
on the high side of the cutting speeds helped.
I'll likely settle on the heat & press method suggested by
PrecisionMachinist. Class is on monday--I'll let you know how it goes.

--
B.B. --I am not a goat! thegoat4 at airmail dot net
http://web2.airmail.net/thegoat4/

In article ,
B.B. u wrote:

[ ... ]

Harold, When you wrote "Can I assume the mandrel is ½?" that last
character came out as Pi on my screen, and I have no idea what you meant
by it.

It comes out as "1/2" on some screens, but since it is a part of
the extended ASCII character set, there are no promises that it will
show up the same on all. This is a primary reason for sticking to only
the characters which show on the tops of your keyboard keys. Anything
which requires fancy keyboard tricks to generate (e.g. Compose-1-2 on my
Sun keyboard) will not mean the same to everybody in this newsgroup with
mixed systems in mixed locations around the world. (And it even chances
on some of them when you change the characterset used by the program.

But, bar stock, pressed the mandrel in with an arbor press.

Hmm ... bar stock? Not turned to have a very slight taper?
That could be part of the problem. I think that the typical taper on an
arbor for turning between centers is 0.001 inch/foot, but I'm sure that
Harold will correct me if I am wrong.

We're using general-purpose indexable carbide tools on all of the
lathes, but I have a fresh bit of tool steel and I'll see about making
my own tool to play with.

That could help, as typically a carbide insert is not as sharp
as a frechly ground and honed HSS bit.

Note that I have some very nice sharp solid carbide inserts
(1/4" IC 55 degree diamond *without* TiN coating or the like, which I
use when I want a sharp tool but am too lazy to grind my own. :-)

I did find (counter-intuitively) that running
on the high side of the cutting speeds helped.
I'll likely settle on the heat & press method suggested by
PrecisionMachinist. Class is on monday--I'll let you know how it goes.

If your arbors *do* have a taper, it should get it that much
tighter. (Also note that the heat generated by turning could expand the
aluminum and loosen the grip on the steel arbor, which would make the
typical carbide insert the poorer choice here.)

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 ---

"DoN. Nichols" wrote in message
...
In article ,
B.B. u wrote:

[ ... ]

Harold, When you wrote "Can I assume the mandrel is ½?" that last
character came out as Pi on my screen, and I have no idea what you meant
by it.

It comes out as "1/2" on some screens, but since it is a part of
the extended ASCII character set, there are no promises that it will
show up the same on all. This is a primary reason for sticking to only
the characters which show on the tops of your keyboard keys. Anything
which requires fancy keyboard tricks to generate (e.g. Compose-1-2 on my
Sun keyboard) will not mean the same to everybody in this newsgroup with
mixed systems in mixed locations around the world. (And it even chances
on some of them when you change the characterset used by the program.

That's one thing I need to try to keep in mind. I'm fairly comfortable with
a half dozen characters so generated and use them routinely. Probably not a
good idea when posting! Thanks, DoN.

But, bar stock, pressed the mandrel in with an arbor press.

Hmm ... bar stock? Not turned to have a very slight taper?

His answer is likely no, and it shouldn't have. Arbors have a gentle taper
and will hold an item squarely, assuming the mandrel is pressed properly and
the item held isn't very narrow.

That could be part of the problem. I think that the typical taper on an
arbor for turning between centers is 0.001 inch/foot, but I'm sure that
Harold will correct me if I am wrong.

Close, but no cigar. Standard taper is .0005"/inch. A tiny taper like
you propose would necessitate a huge array of mandrels to be useful for
run-of-the-mill parts, unless a very tight tolerance was imposed. They
would also have the ability to swage holes effortlessly, which could be a
bad idea depending on circumstances at hand. Mandrels are often used on
grinding machines, where one is grinding the likes of bushings that must be
dead concentric. Hone first for size and finish, then grind. I've ground
literally thousands of bushings in that fashion.

We're using general-purpose indexable carbide tools on all of the
lathes, but I have a fresh bit of tool steel and I'll see about making
my own tool to play with.

That could help, as typically a carbide insert is not as sharp
as a frechly ground and honed HSS bit.

Yep! Rarely do you find inserts that rival honed HSS tools, but they do
exist. I use RB inserts that are diamond ground. Very nice inserts, and
sharp, so long as you don't buy them coated. Even the coated ones are
fairly sharp, however.


If your arbors *do* have a taper, it should get it that much
tighter. (Also note that the heat generated by turning could expand the
aluminum and loosen the grip on the steel arbor, which would make the
typical carbide insert the poorer choice here.)

Yeah, all a part of that delicate balance one must achieve. In practice,
one might never use a mandrel. They are slow, cumbersome devices that
limit the ability to machine anything. Soft jaws are often used instead,
or any of a myriad of setup variations, anything to improve driving
capability and cutting ability. Still, they're a very important part of
learning to run machines, exposing the newbie to precise ways to achieve
certain functions. Learn any and all of these procedures, and learn them
well. Later on, when you have better processes at your disposal, you'll
incorporate them when appropriate. Right now you're learning the basics,
and that's the best way to progress.

Harold

In article ,
(DoN. Nichols) wrote:

In article ,
B.B. u wrote:

[ ... ]

Harold, When you wrote "Can I assume the mandrel is ½?" that last
character came out as Pi on my screen, and I have no idea what you meant
by it.

It comes out as "1/2" on some screens, but since it is a part of
the extended ASCII character set, there are no promises that it will
show up the same on all. This is a primary reason for sticking to only
the characters which show on the tops of your keyboard keys. Anything
which requires fancy keyboard tricks to generate (e.g. Compose-1-2 on my
Sun keyboard) will not mean the same to everybody in this newsgroup with
mixed systems in mixed locations around the world. (And it even chances
on some of them when you change the characterset used by the program.

But, bar stock, pressed the mandrel in with an arbor press.

Hmm ... bar stock? Not turned to have a very slight taper?
That could be part of the problem. I think that the typical taper on an
arbor for turning between centers is 0.001 inch/foot, but I'm sure that
Harold will correct me if I am wrong.

Oh, the mandrel itself is tapered--it's a pre-made mandrel out of a
box. I thought Harold was asking if I was turning my part from either
cast or bar stock. I'm turning from bar stock, and the part is pressed
onto a mandrel. Hope that clears it up.

We're using general-purpose indexable carbide tools on all of the
lathes, but I have a fresh bit of tool steel and I'll see about making
my own tool to play with.

That could help, as typically a carbide insert is not as sharp
as a frechly ground and honed HSS bit.

Note that I have some very nice sharp solid carbide inserts
(1/4" IC 55 degree diamond *without* TiN coating or the like, which I
use when I want a sharp tool but am too lazy to grind my own. :-)

I did find (counter-intuitively) that running
on the high side of the cutting speeds helped.
I'll likely settle on the heat & press method suggested by
PrecisionMachinist. Class is on monday--I'll let you know how it goes.

If your arbors *do* have a taper, it should get it that much
tighter. (Also note that the heat generated by turning could expand the
aluminum and loosen the grip on the steel arbor, which would make the
typical carbide insert the poorer choice here.)

Yeah, maybe I'll just turn it until it starts slipping and then run
it over to the press while still hot.

--
B.B. --I am not a goat! thegoat4 at airmail dot net
http://web2.airmail.net/thegoat4/

"B.B." u wrote in message
news snip---
Harold, When you wrote "Can I assume the mandrel is ½?" that last
character came out as Pi on my screen, and I have no idea what you meant
by it.

Ooops!! Sorry about that----I hit the keys in the wrong sequence, and
didn't notice. It was intended to be ½" ?----asking the size of your
mandrel. My concern is that the more slender is the mandrel, the more
likely you would experience chatter.

But, bar stock, pressed the mandrel in with an arbor press.
We're using general-purpose indexable carbide tools on all of the
lathes, but I have a fresh bit of tool steel and I'll see about making
my own tool to play with.

If you understand rake and clearances, you'd be far better off, especially
if you're using negative rake inserts. If you're using positive rake and
they're sharp with a minimal corner radius, it may not make a big
difference. Regardless of what you have, I'd strongly encourage you to
learn to hand grind toolbits while you have someone looking over your
shoulder (assuming you do have, and they understand the concept themselves),
for it will serve you well for ever. It really is nice to not have to buy
each and every special type tool that you need when it may get used only
once.

Now that we understand you're using inserts, make sure you're not running a
C5 or C6 grade, especially if the insert has looked at steel first. It's
the wrong choice for non-ferrous materials to begin with, lacking the proper
edge hardness to withstand cuts. It really does make a huge difference.


I did find (counter-intuitively) that running
on the high side of the cutting speeds helped.

All metals have what you might call a "sweet spot", where they machine
better than at other speeds. Aluminum really responds well to high speeds,
and rarely is a problem as a result, assuming you use the right tools.
Armed with that knowledge, try to run as fast as possible, which generally
yields far better finishes and improved chip flow. You risk chatter, so
you must achieve a balance for conditions at hand. You can't always use the
speed you might desire. Run as fast as possible for conditions. The
larger the area of contact your part has with the tool, the more likely
you'll have chatter. Broad tools make for difficult operations unless you
have *very* rigid machines. If you were to compare the likes of a 17"
Axelson, for example, with a 10" Southbend (not a fair comparison, but it
really proves the point) it would jump right out at you. When you run a
lathe, try to keep everything choked up as close as possible. Material short
in the chuck, tailstock quill extended only as far as absolutely needed, and
cutting tools held as short as possible. When you keep everything close, you
can usually run faster, which yields better results and shortens machining
time. That can be real critical if you're making lots of the same thing.

I'll likely settle on the heat & press method suggested by
PrecisionMachinist. Class is on monday--I'll let you know how it goes.

Good luck! Hope you can give us a good report.

Harold

In article ,
"Harold and Susan Vordos" wrote:

"B.B." u wrote in message
news snip---
Harold, When you wrote "Can I assume the mandrel is ½?" that last
character came out as Pi on my screen, and I have no idea what you meant
by it.

Ooops!! Sorry about that----I hit the keys in the wrong sequence, and
didn't notice. It was intended to be ½" ?----asking the size of your
mandrel. My concern is that the more slender is the mandrel, the more
likely you would experience chatter.

It's a skinny little 3/8 mandrel and 6" long while my part was only
3/4" long. I had a chatter problem at first (I did kinda like the funky
looking finish, though) but it went away as soon as I limited myself to
passes of .010 or less. Not a problem since I'm only making one wheel
and only needed to shave off about .070 anyway.

But, bar stock, pressed the mandrel in with an arbor press.
We're using general-purpose indexable carbide tools on all of the
lathes, but I have a fresh bit of tool steel and I'll see about making
my own tool to play with.

If you understand rake and clearances, you'd be far better off, especially
if you're using negative rake inserts. If you're using positive rake and
they're sharp with a minimal corner radius, it may not make a big
difference. Regardless of what you have, I'd strongly encourage you to
learn to hand grind toolbits while you have someone looking over your
shoulder (assuming you do have, and they understand the concept themselves),
for it will serve you well for ever. It really is nice to not have to buy
each and every special type tool that you need when it may get used only
once.

Now that we understand you're using inserts, make sure you're not running a
C5 or C6 grade, especially if the insert has looked at steel first. It's
the wrong choice for non-ferrous materials to begin with, lacking the proper
edge hardness to withstand cuts. It really does make a huge difference.

How would I check a carbide for its grade? Would it be embossed on
the inset itself, or would I simply have to check the package it came
out of?

I did find (counter-intuitively) that running
on the high side of the cutting speeds helped.

All metals have what you might call a "sweet spot", where they machine
better than at other speeds. Aluminum really responds well to high speeds,
and rarely is a problem as a result, assuming you use the right tools.
Armed with that knowledge, try to run as fast as possible, which generally
yields far better finishes and improved chip flow. You risk chatter, so
you must achieve a balance for conditions at hand. You can't always use the
speed you might desire. Run as fast as possible for conditions. The
larger the area of contact your part has with the tool, the more likely
you'll have chatter. Broad tools make for difficult operations unless you
have *very* rigid machines. If you were to compare the likes of a 17"
Axelson, for example, with a 10" Southbend (not a fair comparison, but it
really proves the point) it would jump right out at you. When you run a
lathe, try to keep everything choked up as close as possible. Material short
in the chuck, tailstock quill extended only as far as absolutely needed, and
cutting tools held as short as possible. When you keep everything close, you
can usually run faster, which yields better results and shortens machining
time. That can be real critical if you're making lots of the same thing.

I'll likely settle on the heat & press method suggested by
PrecisionMachinist. Class is on monday--I'll let you know how it goes.

Good luck! Hope you can give us a good report.

Harold

--
B.B. --I am not a goat! thegoat4 at airmail dot net
http://web2.airmail.net/thegoat4/

"B.B." u wrote in message
news
In article ,
"Harold and Susan Vordos" wrote:
snip------

It's a skinny little 3/8 mandrel and 6" long while my part was only
3/4" long. I had a chatter problem at first (I did kinda like the funky
looking finish, though) but it went away as soon as I limited myself to
passes of .010 or less. Not a problem since I'm only making one wheel
and only needed to shave off about .070 anyway.


That's even worse than I had expected. While I realize that the number of
passes you may have to take isn't of importance at this point, I think you
can understand that if you were engaged in doing this for gain, you'd be out
of business before you got started. Again, you're in a learning phase
right now, so it's important to experience these things so you understand
them.

Holding by other means, you'd have roughed the flywheel within .03"/side,
then taken appropriate finish cuts of equal sizes for consistent tool load.
One to determine size, the balance (2 passes) splitting the remaining
material, half for each pass. That way you can better control diameter when
it's critical. Certainly, the outside of a flywheel isn't, but it's a good
method to learn for when your project demands precision.


How would I check a carbide for its grade? Would it be embossed on
the inset itself, or would I simply have to check the package it came
out of?

Depends on the maker. Some carbide is identified on each piece, but you
can't rely on that. The C2 designation might appear as something else, so
you have to understand carbide markings for it to make sense. For
example, if you're using Carboloy, their C2 grade would be marked 883, and
C5 would most likely be marked 370. Understand that any carbide will cut
any material, but how they hold up is determined by the grade. C2 has
excellent edge hardness, but is brittle and chips easily. Not a problem when
machining aluminum, but when you machine steel, unless you're taking very
light cuts, it tends to chip the edges around the point of contact, the
result of chips acting against the carbide. The point may very well stay
intact and still cut fine, but if you use the tool for a deeper pass than
the previous one, it often breaks because the tool has lost proper
configuration because of edge erosion.

In the old days, (carbide) makers talked about a triangle. If your choice
gave problems, you moved around the triangle. As you gain one feature, you
give up two others. There's usually a balance of the three features that
will provide good tool service and life. I'm not sure they even talk
about that today, it's been years since I last had to worry about carbide
grades. If you can find some old Kennametal data, they used to include
the triangle, and it would help you understand how it works. It's been too
long for me to recall it correctly.

What's important here is that your insert hasn't been machining steel before
using it on aluminum, even if it's the right grade. The keen edge will be
gone, and without that you're likely to have problems. Finish often speaks
volumes about the condition of the cutting edge, even when you think
everything is OK. If you're machining 6061-T6, you should expect the
surface to show feed marks, but otherwise cut quite cleanly, with no
fuzziness on the surface, assuming you're using a lubricant. If you get the
slightest signs of fuzziness, the edge is likely experiencing some chip
welding, maybe at the microscopic level. That makes for poor machining and
increased cutting pressure. That works against you when using a mandrel,
especially when you're driving with such a small diameter. Knowing the
size you're using, I'd suggest what you're experiencing is more or less
normal. That's why you try to avoid using mandrels. I also avoid turning
between centers as much as I can. Same problem. Too much chatter and the
cuts demanded can't be accomplished. Soft jaws answer the vast majority of
the problems. It's a little too early for you to worry about them at this
point. Besides, the chuck you're using may not accommodate them. Not all
chucks do.

Harold

In article ,
"Harold and Susan Vordos" wrote:

"B.B." u wrote in message
news
In article ,
"Harold and Susan Vordos" wrote:
snip------

It's a skinny little 3/8 mandrel and 6" long while my part was only
3/4" long. I had a chatter problem at first (I did kinda like the funky
looking finish, though) but it went away as soon as I limited myself to
passes of .010 or less. Not a problem since I'm only making one wheel
and only needed to shave off about .070 anyway.


That's even worse than I had expected. While I realize that the number of
passes you may have to take isn't of importance at this point, I think you
can understand that if you were engaged in doing this for gain, you'd be out
of business before you got started. Again, you're in a learning phase
right now, so it's important to experience these things so you understand
them.

Holding by other means, you'd have roughed the flywheel within .03"/side,
then taken appropriate finish cuts of equal sizes for consistent tool load.
One to determine size, the balance (2 passes) splitting the remaining
material, half for each pass. That way you can better control diameter when
it's critical. Certainly, the outside of a flywheel isn't, but it's a good
method to learn for when your project demands precision.

We lose 10 points each time we restart a part, but I'm taking the
class to learn--not necessarily to fluff my GPA. I may very well do
another wheel simply for the hell of it.
Either that or when I get to make my own project up after finishing
this one I'll do something with a wheel on it.

How would I check a carbide for its grade? Would it be embossed on
the inset itself, or would I simply have to check the package it came
out of?

Depends on the maker. Some carbide is identified on each piece, but you
can't rely on that. The C2 designation might appear as something else, so
you have to understand carbide markings for it to make sense. For
example, if you're using Carboloy, their C2 grade would be marked 883, and
C5 would most likely be marked 370. Understand that any carbide will cut
any material, but how they hold up is determined by the grade. C2 has
excellent edge hardness, but is brittle and chips easily. Not a problem when
machining aluminum, but when you machine steel, unless you're taking very
light cuts, it tends to chip the edges around the point of contact, the
result of chips acting against the carbide. The point may very well stay
intact and still cut fine, but if you use the tool for a deeper pass than
the previous one, it often breaks because the tool has lost proper
configuration because of edge erosion.

So what does the C2/C5 rating refer to? Grain size? Carbide vs.
"other" content? Is there some sort of system to choose which grade
where, or is it just down to C2 for some stuff, C5 for others, all other
grades not made anymore?
Searching on google got me a whole lot of marketing, but not much
else.

In the old days, (carbide) makers talked about a triangle. If your choice
gave problems, you moved around the triangle. As you gain one feature, you
give up two others. There's usually a balance of the three features that
will provide good tool service and life. I'm not sure they even talk
about that today, it's been years since I last had to worry about carbide
grades. If you can find some old Kennametal data, they used to include
the triangle, and it would help you understand how it works. It's been too
long for me to recall it correctly.

Sounds like bicycle parts: cheap, durable, light--pick two.

What's important here is that your insert hasn't been machining steel before
using it on aluminum, even if it's the right grade. The keen edge will be
gone, and without that you're likely to have problems. Finish often speaks
volumes about the condition of the cutting edge, even when you think
everything is OK. If you're machining 6061-T6, you should expect the
surface to show feed marks, but otherwise cut quite cleanly, with no
fuzziness on the surface, assuming you're using a lubricant. If you get the
slightest signs of fuzziness, the edge is likely experiencing some chip
welding, maybe at the microscopic level. That makes for poor machining and
increased cutting pressure. That works against you when using a mandrel,
especially when you're driving with such a small diameter. Knowing the
size you're using, I'd suggest what you're experiencing is more or less
normal. That's why you try to avoid using mandrels. I also avoid turning
between centers as much as I can. Same problem. Too much chatter and the
cuts demanded can't be accomplished. Soft jaws answer the vast majority of
the problems. It's a little too early for you to worry about them at this
point. Besides, the chuck you're using may not accommodate them. Not all
chucks do.

These inserts get used on any damn thing that finds its way onto the
lathes. Poor things probably had to cut stone at some point. In fact,
I had to put a steel center into the chuck and take a light cut off of
it so the mandrel would run true immediately before I machined the
wheel. So, yeah, it got "steeled" first.
Would the steel or aluminum--not both rule also apply to HSS bits, or
are they OK with it since they can be sharpened?
I wound up leaving the outside of my flywheel .003" oversize (we have
a tolerance of .005" over/under) so I could file/sand off the uglyness.
Alas, there is no lubricant. I did try painting my wheel with a film
of oil for one cut, but it didn't appear to help any, so I didn't mess
with it any more. Got a bit stinky anyhow.
My lathe actually had two carbides sitting at it. One was undamaged,
but the other had an impressive little heap of metal welded firmly to
the cutting edge.
But that's really nothing compared to the guy who took a .050" pass
using a carbide insert cutter in the mill, but ran it backwards and way
too fast. It took off .050, but as a smear instead of as chips. Ah,
school.

--
B.B. --I am not a goat! thegoat4 at airmail dot net
http://web2.airmail.net/thegoat4/