cutting advice for thick steel

[kirby]

Hi guys,

just wondering if i could get some adivice on a profile milling job i have going on..

Material....2 1/4 inch thick 44W
Part size....25 inches in X by 10 inches in Y at its higest point
cutter....sandvick r290 3 flute carbide ...880 cutting speed with .005" chip load recomended

2nd cutter..2 flute r290 extended length

Problem lies in the fact the cutter i have only can cut up to 1 " deep. I have the parts doweled to flip so i can cut the bottom half. But i also have a longer cutter that i can get through the whole part if needed. But i am worried about deflection.

This is one of those jobs that the cutter gets burnt up or melted if i don't do this right. I don't feel comfortable just setting the speeds and feeds to the max and letting it go.

Any advice would be appriciated. I will answer all questions anyone might have 'cause i know i left something out somewhere.

[kirby]

here is a rough sketch of the part...

Also it is a .75 dia. cutter..

[tyty43086]

If you decide to flip just make sure your part is located pretty close so that the top and bottom profiles match up. If I were you I would rough out the shape within .02 of the final profile with the shorter endmill, then go in with your long endmill and finish, not worrying about deflection with such a light cut.

[big_mak]

I'd Z-axis plunge the profile with the longer cutter, and semi finish with a roughing endmill to take off the cusps, then Finish.

[kirby]

well first thing Sat. morning i melted my new cutter. Then i was left with the longer length cutter. I need to get used to this high speed machining because there is no time to react. I cut the feed and speed down but i left the depth to deep and the cutter failed.(1700 rpm....20 ipm.. .350 depth) I should have cut the depth down to .2-.25 ???

now i am just taking lighter cuts with the long endmill .075 @1600 rpm @13.5imp. I mounted an air line on machine to keep chips clear and i just walk away and let it run. It takes about 2 1/2 hours to cut the part. Not as fast as i wopuld like but i need to get the job done asap because the customer is in a bind and i can't risk losing this cutter. But still it is 50 inches of 2.25 thick steel being cut.

How does one really learn speeds and feeds vrs depth of cut....is it just experience. 15 years of manual machining..went more by feel than theory. That doesn't seem to hold as true with cnc..

[big_mak]

.350 is pretty deep for a 3/4" endmill with inserts.

You have to get used to the dynamics of the machine, and the tool assembly.

Don't be affraid to use roughing cutters either. They are rather efficient tools, and are fairly free cutting.

[kirby]

also the cutters are indexable carbide inserts....not solid carbide...sorry for any confusion,,,