# Got a nice finish on 303 stainless



## spaceman_spiff (Nov 12, 2014)

*material
**rpm**diameter**feedrate**radial doc**sfm**lube**direction**chips**tool**notes*303SS5811.175.005 auto.005 to .010179WD40spindlebreakerTPG322?barely feel finish with nail303SS8601.175.005 auto.005 to .010264WD40spindlebreaker
TPG322?
barely feel finish with nail

Machine: Atlas 10F from 1940's 
Stock held in 4 jaw chuck, center drilled and supported with live center in tailstock. 
Stickout about 3" from chuck.
Insert: I think its a TPG322

thought i'd share..getting a good finish on steel is a small battle and I think this one I had a victory!

the good finish is in the middle..please ignore all the other, uh..."attempts"

the carbide is an insert, with a fairly large radius, i'd say probably 1/32". The one visible in the picture with the sharp corners is the chip breaker installed on top of it, which doesnt actually cut the finish.


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## Wreck™Wreck (Nov 12, 2014)

If the last picture is a chipbreaker atop a tp insert it is way in the wrong place, I am surprised that you didn't scag a bunch inserts beforehand.


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## Holescreek (Nov 12, 2014)

It appears that the insert you're using is too small for the tool holder. It's certainly not in the correct position, you're cutting on the back relief in the photo.


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## spaceman_spiff (Nov 12, 2014)

Wreck™Wreck said:


> If the last picture is a chipbreaker atop a tp insert it is way in the wrong place, I am surprised that you didn't scag a bunch inserts beforehand.



thanks for noticing, yes it is, I have no idea how to use it. how is the chip breaker supposed to be installed?


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## spaceman_spiff (Nov 12, 2014)

Holescreek said:


> It appears that the insert you're using is too small for the tool holder. It's certainly not in the correct position, you're cutting on the back relief in the photo.



the insert thats visible is the chip breaker which is not doing the cutting..I have no idea how its supposed to be installed so I just put it kind of off to the side


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## spaceman_spiff (Nov 12, 2014)

heres a pic of the insert and its chipbreaker..I think the insert is a TPG322


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## Wreck™Wreck (Nov 12, 2014)

One of the most annoying traits of stainless is how soft it is, it often makes large birds nests of chips which wrap around the tool and work causing a poor finish and tool breakage.

A clamp-on chip breaker forces the chip to curl tightly and break (if you are lucky).
Like so.



Increasing the feed rate and/or DOC creates a thicker chip that is more likely to break.

Flood coolant helps a great deal as it cools the chips and makes them easier to break. Negative rake inserts with molded chip breakers are the way to go but are probably not a good match for your machine.

Also skip the WD40 on steel, use a lightweight tapping/cutting compound, biodegradable of course.

TPG 322 insert means
 Triangle Positive Ground, 3/8" IC, 2 X 1/16 thick, 2 X 1/64 nose radius. A TPG 321 insert would make you much happier with a 1 X 1/64 nose radius.


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## Karl_T (Nov 12, 2014)

here's what mine looks like


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## spaceman_spiff (Nov 12, 2014)

ahh thanks guys..so the chipbreaker increases the angle that makes sense..I was thinking somehow it cut the chip duh

These TPG inserts and the holder were basically free so I had to try them out.

I also have a bunch of CCMT and CCGT inserts, so I just bought a holder for them. Those are positive rake although they have a very fine radius..I think I have the "0" versions which are supposed to have no radius. Oh well at least they were free.


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## Wreck™Wreck (Nov 13, 2014)

spaceman_spiff said:


> I also have a bunch of CCMT and CCGT inserts, so I just bought a holder for them. Those are positive rake although they have a very fine radius..I think I have the "0" versions which are supposed to have no radius. Oh well at least they were free.



All tools have some nose radius otherwise they would fail almost immediately. Coated inserts have a small radius on the cutting itself due to the coating process, many negative rake inserts for steel have a visible radius on the cutting edge, this requires a rigid machine to work effectively.


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## Holescreek (Nov 13, 2014)

Just out of curiosity, did you set the cutting edge to the center of the bar before you made those passes?  Place a 6" steel scale between the cutter and the bar and feed the cutter in enough to hold the scale in place. If the scale is standing straight up and down the cutter is on center. If it's leaning back toward you it's below center, if leaning away it's to high.


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## spaceman_spiff (Nov 13, 2014)

Holescreek said:


> Just out of curiosity, did you set the cutting edge to the center of the bar before you made those passes?  Place a 6" steel scale between the cutter and the bar and feed the cutter in enough to hold the scale in place. If the scale is standing straight up and down the cutter is on center. If it's leaning back toward you it's below center, if leaning away it's to high.



The big aluminum block that holds the tool holder I made just for that holder, and it was measured to put the tip of the cutter exactly at spindle centerline, so it should be centered. I dont have that piece chucked up anymore otherwise I'd try the test and see, next time for sure


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## Holescreek (Nov 13, 2014)

You can test it on any piece of round stock, center is the same regardless of diameter.


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## spaceman_spiff (Nov 13, 2014)

Holescreek said:


> You can test it on any piece of round stock, center is the same regardless of diameter.



id have to turn it true first though...so next time I'm working on something I'll check


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## Wreck™Wreck (Nov 13, 2014)

Holescreek said:


> Just out of curiosity, did you set the cutting edge to the center of the bar before you made those passes?  Place a 6" steel scale between the cutter and the bar and feed the cutter in enough to hold the scale in place. If the scale is standing straight up and down the cutter is on center. If it's leaning back toward you it's below center, if leaning away it's to high.



This is a perfectly good way to bugger a nice scale and ruin some inserts. 
Measure from the ways to the tool edge with a scale, write this dimension on the front of the machine, say 8 11/16" for example, then set all tool heights there, it will be more then close enough. All of the lathes in our shop have this dimension written on them with a permanent marker. As a hobbyist you will be chasing tenths anyway and taking multiple passes to reach your finished dimension so adjust accordingly.

That is how I do it and I do this for a living.


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## Karl_T (Nov 13, 2014)

Wreck™Wreck said:


> This is a perfectly good way to bugger a nice scale and ruin some inserts.
> Measure from the ways to the tool edge with a scale, write this dimension on the front of the machine, say 8 11/16" for example, then set all tool heights there, it will be more then close enough. All of the lathes in our shop have this dimension written on them with a permanent marker. As a hobbyist you will be chasing tenths anyway and taking multiple passes to reach your finished dimension so adjust accordingly.
> 
> That is how I do it and I do this for a living.



I've been doing the scale thing 35 years now...

You've got a better way. Not often an old dog learns a new trick.

Karl


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## spaceman_spiff (Nov 13, 2014)

Wreck™Wreck said:


> This is a perfectly good way to bugger a nice scale and ruin some inserts.
> Measure from the ways to the tool edge with a scale, write this dimension on the front of the machine, say 8 11/16" for example, then set all tool heights there, it will be more then close enough. All of the lathes in our shop have this dimension written on them with a permanent marker. As a hobbyist you will be chasing tenths anyway and taking multiple passes to reach your finished dimension so adjust accordingly.
> 
> That is how I do it and I do this for a living.



my main problem is that I have no way to adjust that toolpost I made. well..I can shim the holder up or down a few thou, but thats it. If I open the slot up more I can shim it alot more than that..that might work out. 

But I think I need to make it a "rev 2", where I can install 3/8" tools because I have a ton of those, along with the 5/8" insert holder I have on the way...and then be able to adjust the whole thing up or down say 1/2"...

That little ridge on the cross slide where its reliefed for the toolpost would appear to be machined/ground..maybe I can use it as a reference and make it so my tool post can be rotated and hold 2 or more tools with precision repeatability?

Or should I just dump all of it and get a QCTP? The nice thing about the one I made is how rigid and cheap it was.


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## John Hasler (Nov 13, 2014)

Holescreek said:


> You can test it on any piece of round stock, center is the same regardless of diameter.



Or test it against the point of a dead center.  As Karl says, you need only do it once.  Then you can make a gage (which I've not gotten around to doing).


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## Holescreek (Nov 13, 2014)

Yeah, I've been doing it wrong for 33 years now. Even wronger since I've never ruined a scale or an insert! :roflmao:


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## Wreck™Wreck (Nov 13, 2014)

Holescreek said:


> Yeah, I've been doing it wrong for 33 years now. Even wronger since I've never ruined a scale or an insert! :roflmao:



No offense intended, I am wary of jogging a machine to a scale on the part, how do you do it?
I don't trust these CNC machines all that much. (-:
I did the rule thing years ago on manual lathes, it works a charm.


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## higgite (Nov 14, 2014)

My eyeballs don't seem to be good enough to use the scale trick to reliably get the tool on center. I chuck up a piece of scrap round stock and face it. If it leaves a nub, I know the tool isn't on center and adjust it accordingly. Like John, I'm going to make a height gauge when I get a round tuit.


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## SG51Buss (Nov 14, 2014)

I made a height gauge out of scrap, grub screw for adjustability.  Once the bit height was correct for that zero-nub face cut, set the height gauge to match the bit.  Slight tweaks over time, and keeping track of the overall length with a caliper, got it perfect.

Even though my lathe is a 6", the height gauge currently measures at 2.992".

Go figure...


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## Holescreek (Nov 14, 2014)

Wreck™Wreck said:


> No offense intended, I am wary of jogging a machine to a scale on the part, how do you do it?
> I don't trust these CNC machines all that much. (-:
> I did the rule thing years ago on manual lathes, it works a charm.



It's simple! I don't run a CNC lathe!  I don't get offended over machining stuff, working in a shop for any length of time breaks you of that quickly.  :allgood:


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## Karl_T (Nov 14, 2014)

Wreck™Wreck said:


> No offense intended, I am wary of jogging a machine to a scale on the part, how do you do it?
> I don't trust these CNC machines all that much. (-:
> I did the rule thing years ago on manual lathes, it works a charm.




I take it your lathe doesn't have an MPG (handwheel for fine jog) A CNC without this really hurts. Almost as bad as a manual machine without a DRO. Look into adding this to your lathe, you won't be sorry.

Karl


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## Wreck™Wreck (Nov 14, 2014)

Karl_T said:


> I take it your lathe doesn't have an MPG (handwheel for fine jog) A CNC without this really hurts. Almost as bad as a manual machine without a DRO. Look into adding this to your lathe, you won't be sorry.
> 
> Karl



I can jog 5 tenths at a time, just enough to chip a sharp insert on occasion )-:


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## Wreck™Wreck (Nov 14, 2014)

Speaking of DRO's, the X axis encoder on the manual lathe that I was running today porked the pooch so to speak, my finish OD was 9.5", the Z axis was fine.
I went back to the dial which no one has used in years and it took some work to free up.


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## Karl_T (Nov 14, 2014)

That's a pretty old DRO, Accurite has had membrane keypads for at least 20 years now.

Bet they will still fix it, if you need. Best customer service of any company I know.


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## Wreck™Wreck (Nov 14, 2014)

Karl_T said:


> That's a pretty old DRO, Accurite has had membrane keypads for at least 20 years now.
> 
> Bet they will still fix it, if you need. Best customer service of any company I know.



Thankfully it is the short axis, the Z scale is 100+ inches long on this machine.
It is a Trens lathe made in Eastern Europe, the dials are radius rather then diameter, that will bite me in the butt at some point I'm sure since I move between machines often.


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