manytoys wrote:

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