[busted bit]

most of my experience has been with machining aluminum which obviously has a very big window for acceptible feeds and speeds. i just got a job to machine some steel plate, .25 and .5 thick. i will be doing this on my haas vf-2 vmc. i have an additional coolant pump which flows like a garden hose too. i will have to machine out some 2-3" dia circles and do some profiling. my question is what would be a good end mill to use out of the msc catalog, i usually use 3/8 or 1/2 diameter. i have used carbide in the past but as soon as it cuts a chip it chips the tool so i was thinking of using cobalt (coated?)even if i have to go through a few. the important thing is that i make it through this job and im not concerned about macining fast just accurate with a decent finish.
with the selected tool what would be a good axial depth of cut, ipm feed ,rpm and plunge feed.should i ruff and finish or just use 1 tool to do it? i really need the experienced help here guys, im a metal fabricator with a cnc and have done pretty well but the steel has gave me fits in the past

[DSL PWR]

Well start with a decent carbide endmill. I'd go for a Hanita vari flute. I run my 1/2" at 600sfm (4500 rpm) and about 37ipm (.002/tooth). I slot at .1 deep, and side mill at .2 deep (50% engagement) The tool will do a clean up pass at 1.0 deep and not sing. This is all done on a TM-1, so you should be able to go with a deeper cut and higher chip load on a vf-2. I've never had any issues chipping the mill if I recut a chip.

Good Luck.

[Geof]

Forget the coolant. Go with a TiAlN coated mill and use an airblast for cooling and chip removal. You can run the sfm DSL PWR suggests but if you use a 5/8" 5 flute cutter you can up the feed and take your full 0.5" thickness in one cut.

You mention circles, do you mean holes? How are you programming this CAM or hand?

[Caprirs]

Forget the coolant. Go with a TiAlN coated mill and use an airblast for cooling and chip removal. You can run the sfm DSL PWR suggests but if you use a 5/8" 5 flute cutter you can up the feed and take your full 0.5" thickness in one cut.

You mention circles, do you mean holes? How are you programming this CAM or hand?

Someone is itchin' to show off his newly acquired knowledge.

[Geof]

Someone is itchin' to show off his newly acquired knowledge.

Is this a dig because you know I have mastercam in the company now?

Actually I was going to suggest the Haas G13 circular pocket routine.

[Caprirs]

Is this a dig because you know I have mastercam in the company now?

Actually I was going to suggest the Haas G13 circular pocket routine.

Not the Mastercam. The GeofCAM. You are one of the converted now per your thread .

I just wish my mills were rigid enough to do that sort of cutting.

[davereagan]

If I ran a 5/8" 5 flute slotting in 1/2" material it would sing and probably break unless it was a V carb. A variable helix TiALN coated endmil is definitely the tool for the job. I get great tool life at 400 SFM (3000 rpm for 1/2" endmill). DRY DRY DRY. Turn the coolant on, cut your tool life in half. No CAM system needed. Just a starter hole and then G3 two passes. With the starter hole already done, you can cut a 3" hole in 1/2" thick 1018 in 30 seconds. 3000 rpm, .0025" feed per tooth for the rough pass, then 4000 rpm, .002" fpt for the finish pass. This requires a stub length holder. I would not run a holder with a projection length any longer than 1.75 I prefer the new ones with 1.375" length. A lot of guys on here don't get the difference and try to get the same results with 2.5" or even 4" length holders.

[davereagan]

I dare you to turn the coolant off. Double the tool life. No one is a believer until they are.

[busted blade]

im not scared. i swear . but i am not set up with an air blast. i beleive you. hanita didnt seem to frown upon it (sell more bits, right?). the job is not a long run fortunatley. does it have to do with thermal issues?

[Geof]

.... does it have to do with thermal issues?

Yes, carbide doesn't like to get hot and then quenched; you can get thermal fractures in the cutting edge which lead to premature failure. Another issue with coolant rather than air is that sometimes you cannot clear the chips as effectively so you get re-cutting which can result in chipping the tool.

Having said that I will mention that sometimes if you are really flooding the coolant you can get very good tool life which I attribute to keeping the tool cool all the time because it is running well submerged.

On the stuff I do personally, which is fixtures and prototypes I flip flop between using coolant and running at a modest rate and running dry and really ripping stuff off. My experience is that you have to get things correctly sorted out to run dry and if you don't things can go downhill quickly; running with coolant can be more forgiving.

[busted blade]

my auxilary coolant pump (which im using) is like a garden hose. no evidence of heat at all,like i said chips have a mirror finish on the sheared side and a sandblasted grey finish on the other and is .009+_ thk. almost looks like aluminum. im sure there has to be heat somewhere however small. we'll see

[davereagan]

Getting longer tool life from dry milling happens specifically with one coating: TiALN. A chemist could explain it better, but when you reach a critical temperature at the cutting edge, a layer of aluminum oxide is formed that protects the tool's cutting edge. If you flood cool, this oxidation layer is never formed, and you just get normal life. From what I've read, I don't think even half the guys on here have honestly tried this method.


http://www.mmsonline.com/articles/wh...kes-sense.aspx

http://www.ctemag.com/dynamic.articles.php?id=94

[busted blade]

im wondering if breaking the tool in dry would form the appropriate surface conditioning then go ahead and use the coolant for chip evacuation? if i had a big compressor i would do it dry. i did see the coating begin to degrade after a fairly short period. primarily in the flute where the chip is rubbing. probably at the cutting edge too just not as oblvious

[davereagan]

Excellent question. I don't know. What depth are you cutting? Slotting one diameter deep doesn't REQUIRE an air blast after the first couple of inches, it's just a good idea. I did once have a job that required about 200 slots in 1018 steel, 3/8" wide, 1" deep and 7" long. Chip recutting was a major problem with that job after the first 1/2" in depth. I tried clamping an airline near the cutter and I tried coolant. I think for the final depth I went with coolant, but for 3 diameters deep, it's just a tough job and I always heard some recutting in the last 1/4" of depth.

[busted blade]

yea i hate that sound of the chips gettin cut. my thickest part is .625 which im gonna cut here in an hour or so is a couple 3" holes. just gonna go ahead and clean the whole hole out (only 1 part).
are you ready for this? i talked to tech today at hanita to ask the question about breaking in the tool and he said it makes no difference in life between running it dry and coolant. might have been talking to the forklift driver? also said the coating rubbing off is normal

[davereagan]

I can't believe that guy said that. You're gonna make the whole 3" slug into chips? I'd drill a starter 3/8" hole at X1.3" then run this with a 3/8" varimill assuming a good rigid setup:

:G90
M6T1
G0G95 X1.313 Y0 Z.1 M3S4000 F.002 H1
G1 Z-.35
G3 X1.313 Y0 I0 J0
G1 Z-.8
G3 X1.313 Y0 I0 J0
G3 X1.313 Y0 I0 J0 F.0015
G0 Z1M2

When dropping a slug out, I have broken a lot of varimills when the piece could not fall completely out of the way (ex: only a 1/2" clearance below part in vise, etc) If it dances around, the cutter is in grave danger. Plus, you get a puck you might someday use for something and a whole lot less tool wear.

[davereagan]

I forgot to ask you what length tool holder you are using. I recently picked up some GS holders with a 1.38" gage length. This makes a huge difference compared to a 2.5" gage length holder, especially with a 1/2" or 3/4" endmill.