Feeds and speeds for 304 stainless

[bob1112]

We are doing a light face mill on 304 and it would seem there is a ton of variance of SF and chip loads in charts depending on coatings. Wondering if anyone has a good feed and speed chart with good haul ass numbers for stainless or for all materials for that matter?

Also, we have heard something about machining stainless dry, is this true? If not, what lube is prefered? We have flood coolant now but can coat with straight oil if needed.


Thanks guys

[davereagan]

Hello,
I have found there is a much bigger swing from hogging to finishing speeds with stainless than 1018 mild steel, particularly with endmills. When facing with an insert mill, I run without coolant whether cutting deep or finishing. I have gotten wonderful results with the Maximizer 45 degree type face mill that uses SEKN1203 or SEKN42 inserts. For heavy cutting, I run a 2" 4 flute facemill at 900-1000 rpm, .125" deep and .008-.011" feed per tooth. For finishing, I use a 2.5" 4 flute facemill using SPU424 inserts at 1200 rpm and .0025" feed per tooth for an excellent finish. The stepover is 2.25" and the depth is .002-.003" I use Tap Magic w/EP extra on the finish cut and it helps keep the finish from being gritty. Any grit still left, I can stone off with the fine side of a 6" bench stone. When I first heard that the Tialn coating ran better dry than wet, it was hard to believe. I rarely run enough parts to find out which is better, but I once had a job facing over a hundred 1" thick 316 plates with a nasty plasma cut edge. I was getting 5 parts per index with coolant. I turned the coolant off and got 9 parts per index with the same exact feeds, speeds, etc. It was amazing to see the tool life increase because the heat with that material was extreme. The thing to watch for with stainless is that it will work harden, particularly 316. If a tool is dull, don't push it. You'll take half the life out of the replacement tool just blowing through the edge you hardened with the dull one. Drills can melt down deep in a hole very quickly. The material is costly. Walk away from the machine only when the process is really stable. If you want part numbers for the face mills, email me at davereagan@hotmail.com

[KIMFAB]

When doing 304 I've had real good luck using one of these water based air jet coolants you get from Penn,Enco,Airgas ect for about $100 for the kit
you just mix it up and run it thru a supplied airjet nozzle. it keeps everything real cold, however it gives lots of mist in the air and needs to be cleaned up right away because it dries to a gooey film.