ARGH what speeds and feeds for 304 SS slotting

ARGH!!!! I've just broke my fourth 3/16 carbide endmill. I'm trying to cut slots clear through some 304 stainless steel sheet that's .130 thick in one
pass. I'm using some scrap aluminum under the sheet and cutting about 0.140 deep so I'm going into the aluminum a little bit.
I'm calling it a night. What feeds and speeds would you use? Do I have to do the slot in two passes? Would it help to move up to 1/4" or larger endmills? FWIW, the endmills are all snapping off where the flutes end and the shank begins - no dulling no burning.
Karl
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the slot in two passes? Would it help to move up to 1/4" or larger endmills? FWIW, the endmills are all snapping off where the flutes end and the shank begins - no dulling no burning.

Reduce the feed rate increase the speed of the cutter and use flood coolant, 304 will work harden if you don't have enough coolant running into the cut, i like a sulfur based cutting oil for 304 ( Harvey's #5 ) works well for us.
Best Regards Tom.
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On Thu, 16 Oct 2003 01:39:54 GMT, "Karl Townsend"

It sounds as if your feed rate is a little too agressive.
-- you can contact me via http://aardvark.co.nz/contact /
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Bruce Simpson wrote:

Yes, what Bruce said is likely so. I did a lot of slotting in 17-4 ph with 1/8 th carbide cutters in 1/8 th plate) and I did find the feed rate to be agonizingly slow. But even more important (most) is to drive your cutter into the hilt! Do not allow it to run with a thou more extension then you can get away with. I also try to support my work in such a way that there was nothing below the slot, (to keep the load down and for chip clearance.) Be thankful that the slot goes all the way through because that allows you to do all the cutting almost hard against the holder at the top of the flute. (It is considerably harder when the cut needs to be only part way.)
Bill
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Bill Darby wrote:

I was going to mention the same thing as Bill regarding the open space under the slot. You mentioned going to a larger tool. If possible, absolutely. 304 is not on my list of favorite ways to have an enjoyable day. You simply must stay within the tried and true, acceptable parameters. The stuff will work harden very quickly, sheet, with it's skin on both sides, seems to be even a little less forgiving. That surface skin is a bit tougher, it seems. Keep your rpm down, and don't feed too slow. Full slotting cuts are sometimes blessed with more success using quality HSS & HSS-cobalt, 3 flutes being the ticket. Slotted a bunch of heat treated 17-4 clevisbars for F-16 canopy locks once. The full slotting rough cut was eating a few 2 flute half inch end mills. I recall the part was about 3/4 thick. Got low on 2 fluters and started using 3 flute. Major gain in tool life, I became a convert. Enjoy.
michael
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On Thu, 16 Oct 2003 01:03:39 -0700, michael
......and in reply I say!:
P...PMFJI.
Advice #1

Advice #2

I am but an egg here. My version of milling consists of using a die grinder bit to cut slots out of (mild) steel on a drill press......nudge nudge bind bind say no more....
I lurk to learn for future reference. The same principles apply.
But the above two pieces of advice seem to completely contradict each other. My instincts went with #1, and RAG (Rough As Guts) Engineering bears that out, although sometimes I have found that a slow speed and lots of pressure will do ajob better than the other..... But with "funny" materials, you never know. I want to learn.
You two guys care to thrash it out? ****************************************************************************************** Whenever you have to prove to yourself that you are not something, you probably are.
Nick White --- HEAD:Hertz Music Please remove ns from my header address to reply via email !! <") _/ ) ( ) _//- \__/
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Karl Townsend wrote:

Those 3 flute TiCN coated carbide endmills work well for this. But carbide doesn't like deep cuts so 2 or more passes with higher feed rates .
ff
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looked back to a program for a part I used to make from 17-4, which has

mills at

5/32
tools
17-4 than

FWIW, this is about where I started. Busted them endmills right off.
Karl
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Karl Townsend wrote:

You were using 2 flute end mills IIRC. 3 flute is the ticket for slotting cuts. Likely to get some differing opinions on that, but they worked very well for me. A 3 flute doesn't beat itself to death as there are always 2 of the flutes in the cut. Assuming your setup and machine are reasonably ridgid, I'm thinking the skin is perhaps being a big factor. Also maybe a batch of extra crappy material. I've had situations like yours, milling sheet, that was much more of a bitch to cut than other times, seemed to work harden more readily. Hss may be a better tool in this case, the flexability of the tool can be a big factor. let us know how things work out.
michael
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