Finishing 303 Stainless

Kroll

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Guys I know there is so many variables when it comes to a question like this but maybe an answer will help. I am running the lathe at 250 then tried 400 rpms but just didn't help any.After each pass the finish looks like a pinwheel finish.I am hand feeding at a slow rate and very small cut maybe .002 you know just enough to clean up.My cutting tool is made for SS but wondering about rpms if that is where my problem is.Guy when I cut these these disk which is 1.5dia I am getting a better finish when cutting on the bandsaw.Thanks for any guidance IMG_0506.jpgIMG_0507.jpg
 
I think a little more info would be helpful. What kind/size lathe are you using? Is this a new problem or have you had it since you've been using the lathe? 250 - 400 sounds slow to me, but I defer to the more experienced experts on that one.

Regards,
Terry
 
Kroll, that looks like a CCMT insert. What is the nose radius on it?

The issue is that the tool is deflecting and not cutting. These inserts have to take enough of a bite in order to cut and a 0.002" depth of cut just ain't getting it. I suggest you take a depth of cut at least the nose radius plus 0.003 - 0.005" and speed the lathe up to about 1400 rpm or so.
 
It's a 14"SB,this is first time I ever tried 303,and really only have maybe 4hrs of experience on this lathe.Mike I don't know the radius but its not the one for finish.So like ya'll saying its for removing a bigger cut,I check see if I have one with a smaller radius.I just was trying to take a finish cut to get a smooth finish.Would taking a finish cut with HSS be better? I have some blanks but never grind before
 
Guys ya'll got me looking into the way I have my part mounted which is on an arbor.Which is a 1/2-20 threaded bolt with a nut then a washer which I screw on my part.So guessing its not supported enough to keep it from deflecting,dang Mike I crank up my rpms which is for the first time at 1400 rpm.
So my new game plan is chuck up a piece of 1.5 dia stock the drill tap a hole for a piece of threaded stud so that I can screw the disk on then face it off.
 
303 is a stainless made for ease of machining.
It turns, drills and taps easier then 304 but costs a bit more and gives up some attributes that one would specify SS for in the first place, also it chips far better then 304/316

It is not possible for anyone to make a cutting speed suggestion without knowing the diameter of the part, RPM settings mean nothing without this data.
Being a hobbyist I am going to guess that the part is less then 6" in diameter and that the operation is facing.
Using the tool pictured which appears to be right handed are you facing from the inside out or the outside in?

If you hold the tool that way and face from the outside in you are dragging this tool backwards through the part, this will cause problems.

A conservative cutting speed for such a tool in 303 would be 400 SFM, at 3" diameter the spindle rpm would be around 500 RPM's, I would not run such an operation at less then .005" DOC and .005" IPR feed. Trying to dust off a part with a tool with that large of a nose radius will often prove itself difficult, try a sharper tool.
 
Good questions I wish I would have put that info in my first post,kinda shows I'm new.Its 1.5 dia and I am facing from the inside out.Not using the power feed just doing it by hand so maybe thats also part of my problem.Yes it is facing, I drill and tap the hole 1/2-20 few days ago then today I just wanted to face it just to get good finish which means just removing enough to clean it up better than what band saw cut leaves.The 1.5 dia disk which is 3/8 thick I was screwing it on a threaded bolt then chuck up the bolt and put the disk up against the jaws then face it off just tad
 
Would taking a finish cut with HSS be better?

Stainless likes to work harden so I prefer to use a sharp HSS tool that cuts readily and gets the chips out fast. Stainless tends to hang on to heat so coolant is a good idea, too.

One option is to try a CCGT insert instead of the CCMT. Unlike the CCMT insert, the CCGT has a sharp ground edge that might work better for you. Look up the speed from your insert maker and try it.
 
Good questions I wish I would have put that info in my first post,kinda shows I'm new.Its 1.5 dia and I am facing from the inside out.Not using the power feed just doing it by hand so maybe thats also part of my problem.Yes it is facing, I drill and tap the hole 1/2-20 few days ago then today I just wanted to face it just to get good finish which means just removing enough to clean it up better than what band saw cut leaves.The 1.5 dia disk which is 3/8 thick I was screwing it on a threaded bolt then chuck up the bolt and put the disk up against the jaws then face it off just tad

Chatter, holding a 1 1/2" Dia. part for a facing operation on a 1/4" threaded fastener is sure to end in tears.
Doing this with the tool insert you are using will likely never result in the finish that you want regardless of speed, feed and DOC.

This is unstable work holding at its best.

That is a large nose radius tool, your results would be greatly improved using the same holder with an insert having the smallest nose radius that is available. If a small number of parts are required a HSS steel tool is an option.
 
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