If you are facing a 5" diameter work in a lathe do you increase the RPMs as
you near the center?

--
Michael Koblic,
Campbell River, BC

"Michael Koblic" wrote in message
...
If you are facing a 5" diameter work in a lathe do you increase the RPMs
as you near the center?

--
Michael Koblic,
Campbell River, BC
Yes....

Ed

"Michael Koblic" wrote:

If you are facing a 5" diameter work in a lathe do you increase the RPMs as
you near the center?

Surface feet per minute decreases as you move toward center.

I don't think too many people stop and change speeds as they face though. Start out at
the right speed and accept that you will be slow at center.

My Clausing has a varidrive so I actually could give the speed control a turn as I head in
if I was in a hurry

CNC lathes have a constant surface speed mode that ramps the spindle up as you approach
center. Also have a G code to say do not go about a certain rpm.

Wes

Yes, increasing the speed would be the preferred method.

On a machine with a fixed spindle speed, if the speed was selected for the
smaller portion of the diameter, I expect that there are few lathes that
won't demonstrate some chatter at some point on a 5" diameter facing cut if
the spindle speed remains constant.

As the cutting tool approaches the center, the surface speed (SFM)
decreases, reaching zero at dead center.

This same effect is taking place at the center of a twist drill. The SFM is
essentially zero at the center of the drill point.
The cutting edge SFM increases toward the outer edges of the cutting edges.

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


"Michael Koblic" wrote in message
...
If you are facing a 5" diameter work in a lathe do you increase the RPMs
as you near the center?

--
Michael Koblic,
Campbell River, BC

On Thu, 11 Sep 2008 16:44:48 -0700, "Michael Koblic"
wrote:

If you are facing a 5" diameter work in a lathe do you increase the RPMs as
you near the center?


Yes.

Most CNC lathes have a feature that does this for you when you program
the appropriate command

You also have to do the same when using a cut off tool

However...in most HSM applications, you really dont need to do so.


Gunner

On Sep 11, 7:44*pm, "Michael Koblic" wrote:
If you are facing a 5" diameter work in a lathe do you increase the RPMs as
you near the center?

--
Michael Koblic,
Campbell River, BC

I've never seen a problem when cutting at low speed with HSS.

"Jim Wilkins" wrote in message
...
On Sep 11, 7:44 pm, "Michael Koblic" wrote:
If you are facing a 5" diameter work in a lathe do you increase the RPMs
as
you near the center?

--
Michael Koblic,
Campbell River, BC

I've never seen a problem when cutting at low speed with HSS.

Well, surface finish can go to pot when speeds are too low, and the
variation in speeds across a large face is one of the classic problems in
machining. When CNC came in, a very big deal was made of the fact that you
could program for constant surface speed to overcome the problem.

In some old textbooks you'll see different comments upon it, one of which
was a suggestion to preferentially cut from the center out, adjusting speed
for the minimum that would give you a clean cut near the center and counting
on the heat tolerance of HSS to carry you through to the outside diameter.
This is iffy, of course, but it's the way it frequently was done in
production, back in the days of HSS tools and manual machines in high-volume
manufacturing.

I don't think there's any really good solution with a machine that can't
change speeds during a cut. It's been a while since I read the old articles
and books that talked about it but I don't remember any clear answers. I've
run into the problem myself, which was one of the first things that
motivated me to try using brazed, carbide-tipped inserts on my old South
Bend. They handled it pretty well, especially in cast iron, which was giving
me fits.

--
Ed Huntress

"Ed Huntress" wrote in message
...

"Jim Wilkins" wrote in message
...
On Sep 11, 7:44 pm, "Michael Koblic" wrote:
If you are facing a 5" diameter work in a lathe do you increase the RPMs
as
you near the center?

--
Michael Koblic,
Campbell River, BC

I've never seen a problem when cutting at low speed with HSS.

Well, surface finish can go to pot when speeds are too low, and the
variation in speeds across a large face is one of the classic problems in
machining. When CNC came in, a very big deal was made of the fact that you
could program for constant surface speed to overcome the problem.

In some old textbooks you'll see different comments upon it, one of which
was a suggestion to preferentially cut from the center out, adjusting
speed for the minimum that would give you a clean cut near the center and
counting on the heat tolerance of HSS to carry you through to the outside
diameter. This is iffy, of course, but it's the way it frequently was done
in production, back in the days of HSS tools and manual machines in
high-volume manufacturing.

I don't think there's any really good solution with a machine that can't
change speeds during a cut. It's been a while since I read the old
articles and books that talked about it but I don't remember any clear
answers. I've run into the problem myself, which was one of the first
things that motivated me to try using brazed, carbide-tipped inserts on my
old South Bend. They handled it pretty well, especially in cast iron,
which was giving me fits.

--
Ed Huntress

some times its the metal...

I got some metal that welds real good, but turning/milling no good, as the
engineer at the steel place, where I bought it, "that stuff don't machine
very well, but welding is good"

So, its kept separate from the other metal.

xman

"robert" wrote:

I got some metal that welds real good, but turning/milling no good, as the
engineer at the steel place, where I bought it, "that stuff don't machine
very well, but welding is good"

The other side of the coin is 12L14

Wes

As everyone has said ... YES

On my old import lathe it was a bitch because of fixed speeds. It was a lot
better when I outfited that machine with a DC motor.

On my Clausing 5914 with its varidrie and power crossfeed it's no problem,
kick in the crossfeed drive and twist up the RPM as it cuts in :-)))

This is a MAJOR reason to get a VFD for your lathe...

--.- Dave

"Michael Koblic" wrote in message
...
If you are facing a 5" diameter work in a lathe do you increase the RPMs
as you near the center?

--
Michael Koblic,
Campbell River, BC

On Fri, 12 Sep 2008 15:04:32 -0700 (PDT), Jim Wilkins
wrote:

On Sep 11, 7:44*pm, "Michael Koblic" wrote:
If you are facing a 5" diameter work in a lathe do you increase the RPMs as
you near the center?

--
Michael Koblic,
Campbell River, BC

I've never seen a problem when cutting at low speed with HSS.


The specific problem tends to be that, if you are using carbide or HSS at high
speed, you can get a beautiful finish on the outside. Swarf coming off yellow
or blue (for carbide). At some point towards the centre the speed will fall
into the region where the Built Up Edge phenomenon occurs. The surface finish
will go to hell during this range. As the tool gets closer to the centre the
finish will still be bad, because there is a rough gob of steel welded to the
tip of the tool.

Running HSS below the BUE region all the way will avoid the problem, but can
still benefit form changing the speed as the cut progresses if possible e.g.
from maybe 50rpm at 5" to 250 at 1". This is easy if you have a variable
speed drive. It's a waste of time if you need to do belt changes.

Running carbide above the BUE region can get a bit scary towards the centre of
the part :-)

PS. The best way to get a nice finish is to slap the part on the surface
grinder after facing BEG

Mark Rand
RTFM

You might want to explain the type of surface fininsh you need, which may or
may not be the same results as the type you might be anticipating (depending
upon numerous variables).

Variables.. type of metal, overall size of the workpiece, the type and
condition of the machine(s) being used/available, cutting tool (typically
referred to as bit) geometry and material, operator's skills, and also
speeds and feeds.
Also, using a cutting lubricant, which is nearly always a preference.

With the correct application of variables, the built-up-edge (and
cracking/chipping of the cutting edge) conditions should be completely
avoidable.

The usual rotary table designs are very slow, and unless it's motorized (and
built solidly enough to be used for feeding material while it's being
machined), turning it by hand will result in variations in speed of the
workpiece which will result in changes in the machined finish.

If the application demands that the finish of the surface has to be
precisely flat and exceptionally smooth, then cutting it with a cutting edge
might not be the correct application.
Precision grinding will produce much better finishes, so second or third
operations might be required to attain the required results.

Whether your available equipment can produce the fit and finish that you
actually require can't be anticipated by others without more information
from you.

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


"Michael Koblic" wrote in message
...
Just so I understand: There is a definite BUE range of speeds, you are OK
above or below it (as far as the BUE phenomenon)?
Would an alternative solution be to run a fly cutter over it on a rotary
table?
Thanks,

Michael Koblic,
Campbell River, BC

"Mark Rand" wrote in message
...

The specific problem tends to be that, if you are using carbide or HSS at
high
speed, you can get a beautiful finish on the outside. Swarf coming off
yellow
or blue (for carbide). At some point towards the centre the speed will
fall
into the region where the Built Up Edge phenomenon occurs. The surface
finish
will go to hell during this range. As the tool gets closer to the centre
the
finish will still be bad, because there is a rough gob of steel welded to
the
tip of the tool.

Running HSS below the BUE region all the way will avoid the problem, but
can
still benefit form changing the speed as the cut progresses if possible
e.g.
from maybe 50rpm at 5" to 250 at 1". This is easy if you have a variable
speed drive. It's a waste of time if you need to do belt changes.

Running carbide above the BUE region can get a bit scary towards the
centre of
the part :-)

PS. The best way to get a nice finish is to slap the part on the surface
grinder after facing BEG

Mark Rand
RTFM

On Sep 13, 7:37*pm, Mark Rand wrote:
On Fri, 12 Sep 2008 15:04:32 -0700 (PDT), Jim Wilkins
wrote:

I've never seen a problem when cutting at low speed with HSS.

The specific problem tends to be that, if you are using carbide or HSS at high
speed, you can get a beautiful finish on the outside. Swarf coming off yellow
or blue (for carbide). At some point towards the centre the speed will fall
into the region where the Built Up Edge phenomenon occurs. The surface finish
will go to hell during this range. As the tool gets closer to the centre the
finish will still be bad, because there is a rough gob of steel welded to the
tip of the tool.

Running HSS below the BUE region all the way will avoid the problem, but can
still benefit form changing the speed as the cut progresses if possible e..g.
from maybe 50rpm at 5" to *250 at 1". This is easy if you have a variable
speed drive. It's a waste of time if you need to do belt changes.

That's what I've seen, too, but I'm not sure enough of the details to
post them for posterity. I try to keep the speed below yellow chips
with HSS and up in the blue chips with carbide. If you stop to change
belt speed the bit will leave a ring on the work. Good HSS will take
the heat. A lot of my bits are Medium Speed Steel from Enco, which at
least are easy to grind.

With practice I've learned how to recognize and mostly avoid built-up
edges and their rough finish. In general I think it's from following
the bit grinding and honing instructions in old lathe manuals and
water-annealing bad steel.

For some reason facing out seems to leave a better finish. Maybe it
has to do with wear and play on my 1965 lathe, or because it's a shear
cut.

PS. The best way to get a nice finish is to slap the part on the surface
grinder after facing BEG
Mark Rand

Before I bought one I filed and sanded out the tool marks with a
single-cut pillar file and fine SiC paper on a steel block. The amount
of work involved is -why- I bought the $100 worn-out surface grinder,
which has been very useful for finishing and for sharpening tools.

Wes wrote:
"robert" wrote:

I got some metal that welds real good, but turning/milling no good,
as the engineer at the steel place, where I bought it, "that stuff
don't machine very well, but welding is good"

The other side of the coin is 12L14

Wes

I have read here and other places that leaded steels don't weld well . How
do they braze ? Though it's not likely I will be using any , since my main
source doesn't carry it . Inquiring minds and all that ...
--
Snag
'90 Ultra "Strider"
'39 WLDD "Popcycle"
Buncha cars and a truck

"Wild_Bill" wrote in message
...
You might want to explain the type of surface fininsh you need, which may
or may not be the same results as the type you might be anticipating
(depending upon numerous variables).
big snip

Mild steel disc - 5-8" diameter, 1/8" -1/4" thick.
The desired surface finish is:
a) Flat
b) Even
c) Equivalent to 300 - 600 grit
d) The reverse side finish is less stringent - 200 grit would do.

At this point there is *no* machine available for this. I am trying to
design one to construct from used matchsticks and double-sided sticky tape
(you have to be British to get that reference :-). I am sorting out in my
mind what is the best way of going about it.

So far all I have come up with is an old gramophone player - 33-1/2 to 78
rpm would be just right :-)

--
Michael Koblic,
Campbell River, BC

On Sep 14, 3:37*pm, "Michael Koblic" wrote:

Mild steel disc - 5-8" diameter, 1/8" -1/4" thick.
The desired surface finish is:
a) Flat
b) Even
c) Equivalent to 300 - 600 grit
d) The reverse side finish is less stringent - 200 grit would do.

At this point there is *no* machine available for this. ...

So far all I have come up with is an old gramophone player - 33-1/2 to 78
rpm would be just right :-)
Michael Koblic,

There is, it's called a Blanchard grinder. A wood lathe with a large
faceplate might work, but don't sand or grind on a metal lathe unless
it's too worn for anything else.

The machines used to polish samples in metallurgical labs are
approximately what you need. They look like record turntables but are
much more solidly built since you press the sample against them to
polish it.

No go on the potters' or motorcycle wheel and a pad sander, like we
suggested?

"Terry Coombs" wrote:

I have read here and other places that leaded steels don't weld well . How
do they braze ? Though it's not likely I will be using any , since my main
source doesn't carry it . Inquiring minds and all that ...

Brazes fine. I tend to use high silver content braze but I'm pretty sure copper based
braze works fine.

Wes
--
Reply to:
Whiskey Echo Sierra Sierra AT Alpha Charlie Echo Golf Romeo Oscar Paul dot Charlie Charlie
Lycos address is a spam trap.

"Jim Wilkins" wrote in message
...
On Sep 14, 3:37 pm, "Michael Koblic" wrote:

Mild steel disc - 5-8" diameter, 1/8" -1/4" thick.
The desired surface finish is:
a) Flat
b) Even
c) Equivalent to 300 - 600 grit
d) The reverse side finish is less stringent - 200 grit would do.

At this point there is *no* machine available for this. ...

So far all I have come up with is an old gramophone player - 33-1/2 to 78
rpm would be just right :-)
Michael Koblic,

There is, it's called a Blanchard grinder. A wood lathe with a large
faceplate might work, but don't sand or grind on a metal lathe unless
it's too worn for anything else.

The machines used to polish samples in metallurgical labs are
approximately what you need. They look like record turntables but are
much more solidly built since you press the sample against them to
polish it.

No go on the potters' or motorcycle wheel and a pad sander, like we
suggested?

***********Haven't seen any potter's wheels about at all. As to the bike
wheel I have not tried hard enough yet. I still have a couple of dials to
finish (actually one got finished just yesterday) and then I want to have a
closer look at the 12V motor with gear box I mentioned. If I can get that
one work my prayers may be answered.

On the 24th there is a big tool auction coming up here. I had a look what
they had so far and there *is* a lathe. Looks ancient with bits hanging off
it. It is quite big and space would be an issue. Also could not find anyone
to tell me the details.

A chap near here had a lathe on Craig's list for $600. The info was sparse
to say the least: It turned to be something like a 7X10 Pratt&Whitney bu
that is about it. No pictures ("camera batteries low") and unable to
demonstrate that it actually turns. I gave it up as a bad job.

Local Canadian Tire has a wood-lathe with the lowest speed 500 rpm. Two
reviews gave it 1/5, the thing fell apart on them.

I have also got a 1/3 HP induction motor (I think) sitting on the top shelf.
I have been looking into various modes of transmission (a subject I am even
more ignorant about than others) with a view of pressing it into service.

Yours and others comments about using wood for at least some of the
construction sent me thinking along different pathways.

It's nothing that has to be sorted by tomorrow...

--
Michael Koblic,
Campbell River, BC

On Sun, 14 Sep 2008 12:37:27 -0700, "Michael Koblic"
wrote:


"Wild_Bill" wrote in message
...
You might want to explain the type of surface fininsh you need, which may
or may not be the same results as the type you might be anticipating
(depending upon numerous variables).
big snip

Mild steel disc - 5-8" diameter, 1/8" -1/4" thick.
The desired surface finish is:
a) Flat
b) Even
c) Equivalent to 300 - 600 grit
d) The reverse side finish is less stringent - 200 grit would do.

At this point there is *no* machine available for this. I am trying to
design one to construct from used matchsticks and double-sided sticky tape
(you have to be British to get that reference :-). I am sorting out in my
mind what is the best way of going about it.

So far all I have come up with is an old gramophone player - 33-1/2 to 78
rpm would be just right :-)


Double disk sander


"The American people will never knowingly adopt socialism, but under the
name of liberalism they will adopt every fragment of the socialist program
until one day America will be a socialist nation without ever knowing how it
happened." -- Norman Thomas, American socialist

On Sun, 14 Sep 2008 17:06:02 -0700, "Michael Koblic"
wrote:

A chap near here had a lathe on Craig's list for $600. The info was sparse
to say the least: It turned to be something like a 7X10 Pratt&Whitney bu
that is about it. No pictures ("camera batteries low") and unable to
demonstrate that it actually turns. I gave it up as a bad job.

http://www.lathes.co.uk/pratt%26whitney/index.html

Might want to follow up on it.....



"The American people will never knowingly adopt socialism, but under the
name of liberalism they will adopt every fragment of the socialist program
until one day America will be a socialist nation without ever knowing how it
happened." -- Norman Thomas, American socialist