I am new to metalworking, and am struggling with my new lathe (9x20?)to
achieve decent surface finishes on steel parts. Currently I am working
with bright mild steel, but have just ordered some EN8, EN19 and SS304
to do comparative tests.
I do not have the ability to flood cool the job, I am considering
adapting to flood coolant system for use with soluble oil. Is this
worthwhile?
I am cutting with a Korloy insert tool, 50 m/min speed and 0.1 mm/rev
feed, which is conservative.
Any suggestions ??
I use a little lathe a lot too. Sometimes the parts come out like chrome,
sometimes they look like they'd been sandblasted. The difference is usually the
steel. You are obviously using British terminology -- in the US we call BMS
"drill rod" and it actually makes quite a difference what kind of drill rod I
turn. To get a good finish, I mean.
I really doubt it's your coolant.
I have never heard of Korloy. I'm not going to bother converting your units to
make sense to me. I'm assuming you've looked up the right speeds and feeds. You
can try sharpening a HSS bit and using that. Do your roughing cuts first, and
when you've gotten down to where your machine can handle a rounder nose, use a
tool with its actual tip stoned to about 1/32" radius (that's 0.79375 mm radius)
and use a fine feed. Coolant IMO mostly has two functions: it lengthens the
amount of time a cutter stays sharp, and it lowers the friction path for chips
leaving the cut zone. Both of these can affect finish somewhat, but not nearly
as much as cutter topology and correct speeds and feeds.
One more thing. Are you positive you aren't getting chatter? The modern 9x20
lathes are very light machines, and it's got to be tough controlling chatter on
them. If you look very closely at the turned surface under a strong light, do
you see what look like facets on a gemstone? If so, your machine is chattering
and you can work on trying to control that.
GWE
I'm with Grant on this,
Is your tool post 'ROCK SOLID'.. If your cross slide has a compound on it
and you are not making threads.. get rid of it... make or buy a tool post
that mounts directly on the cross slide and is as big and massive as
possible.
I have an import 9x20 and the compound was a joke and was next to useless
for regular work, let alone cutting threads...
I replaced it with a pretty massive 4-way (about twice the size you'd expect
on a machine this small) and it works GREAT!
I can make better threads just plungeing in parallel on the cross slid than
I could with it.
--.- Dave
That is correct. Drill rod is *not* a mild steel by any stretch
of the imagination.
Probably the nicest machining steel is what is labeled 12L14
here in the US -- a lead alloy to improve free cutting, and low enough
carbon so it is not particularly tough (or hardenable) anyway. What it
is *not* good for is weldability, from what I understand.
What I *don't* remember is what the UK calls hot rolled steel.
(Could they call it the same as the US?)
Enjoy
DoN.
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Aint that HRS? Or is it to simple? :-)
What we have (better use commonly) here (Germany) for free cutting is:
9SMn28k and that would translate to 1.0715
The leaded equivalent would be:
9SMnPb28 (or 11SMnPB30) translates to 1.0718
But to my knowledge, you only get round stock in free machining.
What you call drill rod, is a bit better than what we call (in Germany)
"siver steel", the quality of the Brits silver steel is unknown to me,
but I guess it is either yours, ours, inbetween, or even worse:-)). The
code for the Kraut-silver-steel is 1.2210 (or 115CrV3). A tool steel for
_cold_ work.
The stuff you get here (easily, as always) as CRS*) is
1.0036/1.0037/1.0038 AKA S235JR/S235JRG1/S235JRG2.
Somehow, I _hate_ the naming system. But what I hate most, is that they
seem to change it every 10 years. This (S235JR etc. kind) is the third
system for me.
*)
I know, CRS (or HRS) has _very_ little to do with the quality, but it
has got a common meaning for a distinct alloy.
Nick
On 23 Aug 2005 16:01:34 -0400, snipped-for-privacy@d-and-d.com (DoN. Nichols) wrote:
Chiming in a bit late...
We call CRS BMS==Bright Mild Steel.
We call HRS BMS==Black Mild Steel.
It's simple and it avoids confusion <BG>
regards
Mark Rand
RTFM
I traid a quick conversion in my head to the units I am familar with
and think you, and I think you might do a lot better with a higher
cutting speed. 50 meters / minute is 164 sfm ( I pulled out my
calculator ) and at the low end of recommended speeds for carbide.
Dan
manytoys wrote:
The lesson that should have been learned here is carbide should have long
ago been abandoned in favor of HSS and proper tool geometry. Carbide is a
miserable failure on small machine tools--------the only success it
typically enjoys is the incredible ability to allow the operator to avoid
learning to properly sharpen cutting tools. I hardly think that's a good
thing.
A comment on surface finish. Mild steel, which appears to be the topic
of discussion, is amongst the worst of materials to machine in that it loves
to tear. Only when carbide is employed along with a high surface speed and
proper depth of cut and feed will it cut otherwise. The addition of
lead to steel makes it machine beautifully----so if you'd like some success
with surface finishes, try machining some of it. Your metals supply house
could provide you with proper designations.
304 stainless is ugly to machine, but tends to cut with a good surface,
assuming you have a sharp tool, and don't run it too fast. If you're
intent on using carbide, be certain you do *not* use a C5 or C6 grade. C2
is the proper grade, and it makes a serious difference in tool life and
success. Better yet, for a small lathe like you have, a properly ground HSS
tool with positive rake and a chip breaker is even better. If you'd like
to machine stainless that is fun to cut, buy 303 either S or Se, each of
which are free machining, unlike 304. It cuts with a clean surface,
although not quite as shiny as does 304. 416 is also a free machining
grade, and is capable of heat treatment, should you have need.
Good luck!
Harold
That would have been my suggestion as well. As for where -- it
depends on how much length you want. There are several on-line metal
vendors who will sell you short pieces at premium prices.
But -- if you are willing to purchase (and have the ability to
store) longer pieces, try to find a local steel vendor and buy it in 20
foot lengths (I think that is the standard length.)
EBay auctions offer small pieces of lots of interesting steels
and other metals, but the shipping can be a killer, as most metals and
alloys are quite heavy.
And -- if you are part of a local metalworking club, group
purchases are a possibility. Either with new prices for the long stock,
or with some eBay auctions which are lots just too large to be within
the reach of a single bidder.
We have one member of our local club who specializes in what he
calls "stolen chickens" -- which are often things being gotten rid of by
his previous employer (before he retired). He still supplies such
things, and they appear a the meetings, often with a feeding frenzy.
There was a lot of hex 12L14 on eBay a year or two ago for which
we got together a list of who would commit to buy how much, and once we
had enough subscriptions, the buy was made. Since he is retired, and
has both a pickup truck and a trailer, he was able to drive some
distance to pick up the metal, and brought it back to distribute it.
The size was just the maximum hex which would fit through my 12x24"
Clausing's spindle with the 5C collet drawbar removed, so it worked out
quite nicely for me.
Perhaps you can get together a similar club activity.
Enjoy,
DoN.
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The new(?) USPS Flat Rate box would be a great opportunity for an eBay
seller. For $7.70 he could ship the 11" x 8.5" x 5.5" Flat Rate box
full of steel anywhere in the U.S. Theoretically, that could be 145
lbs of steel. The USPS says "no weight limit", but I wonder. Oh,
wait, there's also an 11-7/8 x 3-3/8 x 13-5/8 Flat Rate box that's
somewhat bigger. Same $7.70. Bob
Depending on the type of steel and the vendor, you may as often find
that 12 feet is the standard bar length. At least it was for 1-1/4"
12L14 and 7/8" 1018 CRS when I bought a copple of pieces at American
Steel in South Portland, Maine a couple of months ago.
It was a nice surprise to find that they were again consumer-friendly,
even taking credit cards. A few years back, they wouldn't sell to me
and insisted I go down the street and order through a customer - he
phoned in the order, I paid hoim, and I picked it up - even though I
knew exactly what I wanted, a single bar of 1-1/2" 12L14, and had cash.
Only disappointment this time was finding I'd left a hacksaw and
measuring tape on the step bumper....
John Martin
Yes, I noticed they've been much more accommodating as
well. They've always been willing to sell to me as a
business, but getting them to make a small delivery down
here in Harpswell was like pulling teeth for a while. Last
time it was no problem - "We deliver down there twice a
week."
You might want to check out Yarde's Drop Zone as well. Very
good prices and delivery isn't too expensive for stock
coming out of CT, if you arrange it in advance. I use
Leighton's express (in Falmouth, I think). 300-400 pounds
of steel is usually around $40 for the freight. UPS isn't
too bad for aluminum.
http://www.yarde.com/cgi-bin/dropzone.pl
Ned Simmons
topic
loves
and
success
house
You've noticed that 12L14 has already been mentioned a few times. It's not
the only free machining mild steel, however. There are others, commonly
known as screw stock, or material for screw machines. 1213 and 1215 are
two more numbers to keep in mind. These two are resulphurized and
rephosphorised to improve their machining qualities, and contain no lead.
They are rated @ 136% for machinability, based on 1212 @ 100%. 1018 has a
machinability of only 78% as compared to 1212, so it's clear that these
materials are far superior for machining, although they may suffer in
mechanical areas. They are not recommended for parts subjected to severe
fatigue stresses.
In addition to 12L14, there is another leaded material, 11L17, which is a
high manganese alloy. It has good machining qualities and can be
carburized, in spite of the small amount of lead in its makeup. 1117,
without lead, isn't quite as good for machining (rated @ 91% based on 1212
as 100%), but is still far better than 1018.
If you require a tough material with excellent strength, but don't want to
heat treat, consider using Stressproof (1144 Hi Stress) or Fatigue -Proof.
These materials have excellent machining qualities, along with tensile
strength far superior to the other materials. Stressproof and Hi Stress
have a tensile strength of 100,000 PSI, and Fatigue-Proof is greater at
140,000 PSI. All of them are rated at approximately 80% machinability as
compared to 1212 @ 100%. These materials cut very well, without tearing,
and tend to cut better with HSS than carbide, at least from my personal
experience.
Where? Large supply houses have them. I used to buy from Jorgensen Steel,
now known as EMJ.
http://www.emjmetals.com/emjonline/index1024.htm
Harold
Great thread! Which of the free machining steels and SS varieties are the
best for welding? Sometimes these machined pieces need to be welded to
something. I know 12L14 isn't reputed to be great...
Peter
Sadly, none of the free machining steel or stainless grades are recommended
for welding. 1117 can be welded with mixed results according to Jorgensen's
stock list. You should consider their use only when no welding is required.
Harold
Thanks for all the good advice. I have some work to do sourcing
equivalents in South Africa, but our steel industry is fairly good. I
know stainless 303 is available on order. I will collate all the info
and the results of my experiments an post it when completed.
Seems I will have to learn to grind HSS, damnit....
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