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Recommendations for milling A2

SeymourDumore

Diamond
Joined
Aug 2, 2005
Location
CT
Guys

I'm starting a relatively large production job on A2.
I have machined quite a bit of A2 before in small batches, one-two pieces, small amount of removal etc etc. I can cut it without issues so not afraid of it at all.
But!

Since this is a production run, I'd like to ask a couple general questions regarding the roughing only.
1: The obvious... speed and feed
2: Coolant or not
3: tooling: serrated rougher or std endmill
4: Stepover

Conditions:
The tool in question is:
1/2" EM.
Max DOC is .450
Very minimal amount of slotting
good access to features, good chip evacuation so no chip recutting
part is held in hard jaws .350 deep, so it's solid.
Stock size is 3"long x 2"wide x 7/8 thick

Currently running a serrated rougher @ 400SFM, .450 max DOC, 40% stepover, .003IPT
Machine is a 40 taper, 7500RPM and gearbox.
I have the ability to flood, minimum oil, airblast or all of the above at my disposal.

The only thing I need to worry about is that all features must finish +/-.001, and stay that way after unclamping.
I have made 20 pieces so far as a test and not overly happy about the tool life on the rougher.
Holding the tolerances were a piece of cake, but I am about to reprogram the part for the long run ( 750 pcs total )
Would an HSM toolpath be OK, or would it put too much stress into the part?
Ditto for dry machining.

Finish part will be hardened to RC60+ and then ground on ... well, on a whole bunch of surfaces as some of the features are .0004 total, so I'd like to do everything
I can to make it easy on the poor guy doing the grinding.

Any suggestions are welcome!

Thank You
 
What's the failure mode of your current rougher? Edge breakdown, coating failure, ?? What was your coolant, air or mist choice?

Going just with the info we've got, I'd say up your FPT to get a bigger bite per flute, .003/T sounds awfully light for a rougher. Be sure the coating is a good choice for your coolant or air blast strategy, maybe slow down SFM if you're getting wear failure. Is the machine itself good and stiff? Short toolholder?
 
Sidelock holder, Haas VF4, flood coolant.
The roughers appeared to have the tips of the serrations wearing and due to overloading, one broke right at the holder while the other lost one of the flutes which ate the others.

I once had a huge ass 4140 job, which I've machined dry, 50% DOC, 20% stepover, 800 SFM/.008IPT using 4FL variable flute standard endmills.
Insanely good tool life, BUT! Those parts were roughed near-net, heat treated, welded and then finish machined after HT @ 45RC.
This is not an option here.

And just to add to my original post, cycle time isn't as much of an issue for me as I'm planning to run 2 machines on the same job and it'll be fine.
It is reliability and least amount of babysitting that I'm concerned with.
 
Stub rougher or full length (~1.25)? I'd use a stub, and if you want to stay sidelock get a couple stub sidelock holders. I'd also try lowering the stepover (~25%), increasing FPT (a lot, maybe .012" to start) and use an air blast rather than coolant. Use a high-temp coating, then double check with the manufacturer for their initial SFM/FPT settings.

My thought is more bite, less wear (at risk of mechanical breakdown when you go too far), more heat to allow the coating to work, air blast ditto and to prevent thermal shock failure, as well as to prevent recutting chips - I hate recut when working with steels.
 
You don't need a serrated rougher, I would try a stubby variable helix end mill with a decent corner radius.
As for speeds and feeds for slotting, maybe start out at 220sfpm .002ipr
I always use flood coolant with A2 without any issues but that's just out of habit.
 
You don't need a serrated rougher, I would try a stubby variable helix end mill with a decent corner radius.
As for speeds and feeds for slotting, maybe start out at 220sfpm .002ipr
I always use flood coolant with A2 without any issues but that's just out of habit.

Mtndew, the .002ipr - is this correct? For full slotting, perhaps, but otherwise sounds far too light. ??
 
I would be using a TiAlN coated cutter and roughing dry. 500SFM and .006"/tooth at 15-20% stepover. HSM toolpaths are fine. Then coolant for everything else.
 
You will get the best tool life with minimal lubrication system. We have done alot of testing and it's no contest.
Coolant worst then dry then air blast them min lube. This is highspeed machining 500-600 sfm full flute depth and 8-10% step. If going that shallow have you checked time on high feed cutters? A2 is very stable in ht
 








 
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