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I understand that cutting speeds published in the books are generally used for large machines, and that they are totally inappropriate for our 'toys'. (I have a 7x12). We should go by what feels right.

I am looking for a little guidance here. Say I machine 3/8" or 1/2" 1018 steel. Where should I be approximately? I have an inexpensive indexable toolset from LMS. The surfaces I get are nothing to write home about... Can anyone with some experience steer me in the right direction? Should I always apply cutting oil? How much to remove in a pass? What speed? I am on the low range. What dial setting appr.? It seems easier to take a heftier cut than a small cut... something seems wrong ;-) Is there something like a lower limit for a lathe cut?

I get by, because I don't need a good finish on these simple bushings I make, but I sure would like to do it better eventually.

Thanks for any pointers!

--
Regards,
Rich
========================================
Richard Kleinhenz
mailto:woodnpen@...


========================================

Rich,
I'm getting good results on mild steel like 1018 using HSS tools with no
coolant. What type of inserts are you using? I haven't gotten as good
results with coated carbide inserts no matter what I seem to try. Carbide
generally likes higher speeds and deeper cuts.

The HSS inserts from LMS in indexable tool holders have worked well for me,
as have ground HSS bits.
I'm getting a good finish with relatively light cuts anywhere from .001" up
to about.020". For 1/2" diameter, I'd have the dial on my machine about
halfway on the low range. Assuming that's about 600 rpm, I think we're
talking about 75 feet per minute surface speed, which is well under the
recommended max for turning mild steel.

I'm also getting better results with steel now that I have completed the JWE
compound mods and have a good size QCTP (series 100). It's more massive and
more rigid than the stock mini lathe toolposts. You also have to make sure
you have the gibs on the cross slide and compound snug.
Also, if you're turning a workpiece longer than about 2 or 3x the diameter,
you probably need to have the tailstock end supported by a center.
Otherwise it will deflect and give you a bad finish.

I'm sure other people may use different setups, but that's what has worked
best for me.
B Flint

Rich, I wouldn't say that the speeds are totaly inappropriate for the
7x's, but I would use them as a general guide. For most steels, I
generally run at a lower speed, typically between 9:00 and 11:00 on
the dial (in low range), and with aluminium, I run at higher speeds,
typically 10:00 to 1:00 on the dial. The finish is more of a
function of how deep you're cutting and the type of toolbit you're
using. I use predominatly carbide (brazed/cemented & inserts) and
get a pretty decent finish. On the roughing cuts, I'll go anywhere
from about .015 to .020 on steel, as much as .050 on Al. I let the
machine tell me when I'm a little too aggressive, usually groans or
chatters if I'm taking too much (or stalls when it hogs in)... For
my finishing cuts, I generally only go .001 - .002 deep and speed up
the machine (around 11:00 to 01:00 for steel, 01:00 to 05:00 for Al)
and manually advance the carriage. I always use some form of lube,
usually "tapmagic", applied with a small brush to the rotating piece
and I'm usually pretty happy with the result. I keep some strips of
400 grit wet/dry close by to polish a little while rotating also (be
careful it doesn't pull you in). The finish is generally better also
if you use a more blunt or rounded radius on the toolbit with light
cuts rather than a sharp pointed one, in my experience.

Ed

--- In 7x12minilathe@..., Richard Kleinhenz
<woodnpen@o...> wrote:

I understand that cutting speeds published in the books are

generally used for large machines, and that they are totally
inappropriate for our 'toys'. (I have a 7x12). We should go by what
feels right.

I am looking for a little guidance here. Say I machine 3/8" or

1/2" 1018 steel. Where should I be approximately? I have an
inexpensive indexable toolset from LMS. The surfaces I get are
nothing to write home about... Can anyone with some experience steer
me in the right direction? Should I always apply cutting oil? How
much to remove in a pass? What speed? I am on the low range. What
dial setting appr.? It seems easier to take a heftier cut than a
small cut... something seems wrong ;-) Is there something like a
lower limit for a lathe cut?

I get by, because I don't need a good finish on these simple

bushings I make, but I sure would like to do it better eventually.

Thanks for any pointers!

--
Regards,
Rich
========================================
Richard Kleinhenz
mailto:woodnpen@o...


========================================

Relative newbie chiming in here. I've had a bunch of experience with
this lately, turning some 1 inch Al down to 0.5 inch in the center of
a shaft. I'm finding that these 7x12s can hog out up to 0.020 inch
with either a HSS or a cemented carbide bit, but the finish is not
very good. I use this for a roughing cut to remove a lot of material
quickly. The speed is about at the 9:30+- position in the LOW range
using a slow and even hand feed on the carraige.

Then, back off the bit and skin off 0.001 or 0.002 on each pass with
the speed dial about 12:00-1:00 until I arrive at my final diameter.
I find I can get a good finish with the carbide bits, a better finish
with a sharpened HSS. Patience is the key. Dry or lubed with TapMagic
seems to make no difference on the Al. Finish it off with emory cloth
(s). Another Yahoo group recommended using polish while the piece is
still on the lathe, but I haven't gotten that far yet.

In general, I'm not too pleased with the commercial carbide bits, but
I think they are cheapy Enco bits. If I buy carbides in the future,
I'm going to buy some top quality ones and see how they do.

Larry
New Orleans

--- In 7x12minilathe@..., "Ed Paradis" <eparadis@a...>
wrote:

Rich, I wouldn't say that the speeds are totaly inappropriate for

the

7x's, but I would use them as a general guide. For most steels, I
generally run at a lower speed, typically between 9:00 and 11:00 on
the dial (in low range), and with aluminium, I run at higher

speeds,

typically 10:00 to 1:00 on the dial. The finish is more of a
function of how deep you're cutting and the type of toolbit you're
using. I use predominatly carbide (brazed/cemented & inserts) and
get a pretty decent finish. On the roughing cuts, I'll go anywhere
from about .015 to .020 on steel, as much as .050 on Al. I let the
machine tell me when I'm a little too aggressive, usually groans or
chatters if I'm taking too much (or stalls when it hogs in)... For
my finishing cuts, I generally only go .001 - .002 deep and speed

up

the machine (around 11:00 to 01:00 for steel, 01:00 to 05:00 for

Al)

and manually advance the carriage. I always use some form of lube,
usually "tapmagic", applied with a small brush to the rotating

piece

and I'm usually pretty happy with the result. I keep some strips

of

400 grit wet/dry close by to polish a little while rotating also

(be

careful it doesn't pull you in). The finish is generally better

also

if you use a more blunt or rounded radius on the toolbit with light
cuts rather than a sharp pointed one, in my experience.

Ed

--- In 7x12minilathe@..., Richard Kleinhenz
<woodnpen@o...> wrote:

I understand that cutting speeds published in the books are

generally used for large machines, and that they are totally
inappropriate for our 'toys'. (I have a 7x12). We should go by

what

feels right.

I am looking for a little guidance here. Say I machine 3/8" or

1/2" 1018 steel. Where should I be approximately? I have an
inexpensive indexable toolset from LMS. The surfaces I get are
nothing to write home about... Can anyone with some experience

steer

me in the right direction? Should I always apply cutting oil? How
much to remove in a pass? What speed? I am on the low range.

What

dial setting appr.? It seems easier to take a heftier cut than a
small cut... something seems wrong ;-) Is there something like a
lower limit for a lathe cut?

I get by, because I don't need a good finish on these simple

bushings I make, but I sure would like to do it better eventually.

Thanks for any pointers!

--
Regards,
Rich
========================================
Richard Kleinhenz
mailto:woodnpen@o...


========================================

Richard,
Definitely try HSS, as an experiment for your own education under your own shop circumstances if nothing else. HSS just seems more forgiving to me, and I get better results since I haven't seemed to crack the "carbide code" yet. HSS will wear faster, but for me, that's a small price to pay for better, more consistent results.

B Flint

Thank you both, looks like I am in the ballpark, in general. Maybe I need to try HSS rather than carbide inserts.
m
--
Regards,
Rich
========================================
Richard Kleinhenz
mailto:woodnpen@...


========================================