[mechatoine]

Hi everyone, Well as the title says, I am trying to machine some 4130 cast steel parts that are mounted on a rotary fixture and not having much luck. (see all the pictures)
First of all we are having to grind the really hard scale on the outside because it's literally like trying to machine 10 grit sandpaper.....
I have tried every maching technique I can think of, from Roughing with a cobalt roughing mill, to our standard Hanita solid carbide endmills, to indexable tools and even took a shot with high speed machining techniques.
We only use high quality tools and the machine is a brand new, extremely rigid AWEA SP3016 with 8000RPM, 30HP motor, CAT50 spindle.
Every time, same result: The cutting edge of the tool is dull and full of micro-cracks as you can see in the pictures.

So here are all the questions I am asking myself:
- Is my fixture the problem?
- Maybe feed and speeds problems?
- Material problems?

Any suggestion, idea or personnal experience machining 4130 cast steel is greatly appreciated

Link for the pictures >>> 4130 Machining Problems - Album on Imgur

[slowlearner]

Have you tried having the castings annealed?

[mechatoine]

Have you tried having the castings annealed?

We had a talk about it with management and it may end up being our solution if we cannot machine it whatsoever. But the extra cost throws us right into a wall. We aren't a job shop, but an OEM for sawmill equipment and cannot raise our prices that easily. Now, how does the annealing process work and how does it affect machinability?

[MaCon]

What oil are you using? Mobilmet 766 comes to mind.

or, If you must use coolant: Hansterfer's S-1001 at about 7.5
Rustlick WS 50-50 at about 9 (Refract. Brix scale readings)

The End Mill holder looks like it needs to be about 10 feet shorter! (uh, sorry, some few INCHES shorter : - )
Are your clearance issues so bad you need all that extension? Vibration is Nearly guaranteed, at that length.
It looks like your tool guy (or you) designed the fixture to help reduce the extension length.

Any chance of throwing the Rotary out in the Parking lot and go direct to the Table? (Or on a Riser, if your Z is limited.)
Any chance of shoring up underneath and beef up the clamps? (they look anemic, to me)
Maybe the swing/snap clamps could wait out in the Parking lot with the Rotary contraption? : - )
If keeping the rotary, maybe add Jack screws up from table, with clamps, to stop some of the resonance (near center of span ).

I'm guessing Hanita Cobalts around 60SFM & .0015"perFlute, under good quality cutting oil (flood), in best rigidity.
Finish cut probably needs Cobalt as well. 70SFM & .0011"perFlute, under good quality cutting oil (flood), in best rigidity.
(Lack of Rigidity usually kills carbide.)

IMHO this all related to Rigidity and Oil!
Rigidity is mandatory! (See your micro cracking on cutting edge.)

Oil &/or coolant quality = Tool Life!
Skimping on same = Why bother with the mess!

Best of Luck.
Later.