Machining A2 steel

[g30u0w0]

Ok, hello all. Ive been a member for all of five minutes so be patient.
I have a question I need help with-machining A2. I am not accustomed to machining anything quite this hard(60-70 rockwell). Can someone help with speeds and feeds.
I am using a Daewoo Puma 2000sy. Running 1 1/8" stock. Flood coolant (about 8%)
Lathe work-
Using adequate inserts/geometry (manufacturer suggested).
Running about 2000 rpms at .008/rev. at a depth of .05" (.015" nose radius on insert).
Not sure if this ok for long term work/tool life.
Please any suggestions.
Surface footage?
Max/Min depth of cut? (ball park)
Getting good heat transfer into chip, but better to see blue chips? black?
Generally, any info will be helpful.
TY,
G30

[DareBee]

Must of my hard work is re-faces, which are usually 1-offs (read - I don't need to make high cycle speeds for the job).

I am happy with CBN tipped insert cutting DRY.
Around 300SFM and 5 at 5 (5 thou dp 5 thou feed).

[g30u0w0]

TY for the info. I appreciate it.

[neilw20]

Blue, Black, sometimes on fire. Keep the energy in the swarf.
Coolant quite often heat treats the swarf and th HP can go UP.
Try it dry.
To much fire? Reduce the speed.
Don't try to take less than 5 thou. DOC.
2 to 5 thou per rev feed, sort of whistling noise quite normal.
Can be spectacular on 6 foot diameter rock crusher cones! Heh Heh.
If you have problems keeping inserts in one piece you need ceramic inserts.
Round ones are are good. The have lots of faces!
Hope (for your sake) it is not an intermittent cut.

[g30u0w0]

Originally Posted by neilw20 Blue, Black, sometimes on fire. Keep the energy in the swarf. Coolant quite often heat treats the swarf and th HP can go UP. Try it dry. To much fire? Reduce the speed. Don't try to take less than 5 thou. DOC. 2 to 5 thou per rev feed, sort of whistling noise quite normal. Can be spectacular on 6 foot diameter rock crusher cones! Heh Heh. If you have problems keeping inserts in one piece you need ceramic inserts. Round ones are are good. The have lots of faces! Hope (for your sake) it is not an intermittent cut.

TY Neil,
I will try it dry. You think a depth of .05 is deep enough or should I take a bigger bite?
What would you say is an approx SF you would stay within. Whistling is not the sound I'm getting so I will have to experiment. I get more like a grinding wheel against steel kind of sound. Appreciate the input. Ty again.
G30

[neilw20]

If it is a grinding sound, is the tool surviving.
Sounds like it has lost it's edge.
This is all done by ear mostly!
You might be too slow. How are the chips.
Breaking int small pieces (lucky) , or stringy? (unlucky unless they burn)
If it is an unmachined surface initilally, you may get more of a grinding sound as the crust is often harder. Try more or less DOC.
Hot chips, cool work sort of hot tool.

[g30u0w0]

Originally Posted by neilw20 If it is a grinding sound, is the tool surviving. Sounds like it has lost it's edge. This is all done by ear mostly! You might be too slow. How are the chips. Breaking int small pieces (lucky) , or stringy? (unlucky unless they burn) If it is an unmachined surface initilally, you may get more of a grinding sound as the crust is often harder. Try more or less DOC. Hot chips, cool work sort of hot tool.

Neil,
You are right, I am only really getting the grinding sound on the first layer. Tool is surviving, but has blackish marks on the yellow insert tip and surrounded, as if it was spray painted exactly on the cutting edge and the paint ran a little. Chips are better-very good blue and kind of the oil slick on the driveway look. I will keep messing with it. Is the color normal insert wear for steel? I have a few inserts to mess with and they were not too expensive. They are from Rouse Arno as I do a good deal of brass and aluminum and just changed out my inserts for ones geared toward tough steel. So not too much of an investment yet.
TY,
Chris

[neilw20]

Chris.

The harder you push it the better it gets.
You will soon find the limits.
If much over hang on work that will limit you because of stiffness.
Looks like you will have spectacular results to show people.
Arrange your sequence and depth of cut for each pass of similar DOC.
Make sure finish cut is heavy.
You can hold size quite well with a bit of practice.
Measure TWICE, cut ONCE for the finish cut.
Believe your micrometer, and calculate DOC for finish.
Everything flexes so on a CNC you sometimes even arrange a curved/tapered finish cut to end up with a parallel result!
Program a parallel path first, then measure every 1/2" or so and try a curved path.
Much bending, and compensating, fine tuning.
I've done heaps of horrible hard things.
When it is all working you can get a verry good surface finish.
Try a few different inserts out of your junk box.
It is surpising what some of them can do.
Just a slightly odd chip breaker or different rake can make a world of difference.

Good Luck
Experiment, Document then Success improves. Its ALL fine tuning.

[AMCjeepCJ]

I have a HUGE write up on milling not turning D2 at 61 rockwell here

http://cnczone.com/forums/showthread.php?t=38898

It has a BUNCH of pictures too, I know it's not exactly the same but A2 and D2 cut just about identical in my experience, A2 might be a little easier... It wouldn't hurt to read it, there are a few good tips in there!!

later~

[AMCjeepCJ]

I apologize if this was already discussed I'm in a hurry to get somewhere so someone else may have mentioned this already but negative rake cutters will work the best on your application... If you read my thread you'll learn about the curie point of metal and how that affects machining prehard materials...

Good luck!

[g30u0w0]

that was a great post, regarding D2. Learned alot. The curie thread was really cool too. Thanks for the help.

[AMCjeepCJ]

Anytime!! Glad you learned some stuff... I had such a hard time finding info on this topic I decided it would be worth documenting it for people who ran up against a similar problem... Glad I stumbled across your thread...

If you learn anything worth sharing, please post it on here!!