[DMF_TomB]

I've trashed 4 x 1/4" and 1 x 1/2" endmills on the same workpiece.
My most recent attempt was:
1/4" endmill, 3850 RPM (252 SFM), 10.78 in/min xy feed (0.0007 in/tooth), 7.7 in/min z feed (0.0005 in/tooth). Step over is 20% of tool diameter (0.0500"), plunge depth is 0.0250".
I've also tried around 1000 RPM, around 4 xy feed, 1 z feed, the tool actually died much faster this way. The material is 304 stainless steel, the cutters are TiALN coated carbide from MariTool.

My mill is an old interact 1 mk 2, 9.5 HP, workpiece is clamped hard to the table with a waste plate of Al underneath so I can mill through into that. I get a lot of chatter at slightly lower RPMs (around 3000-3300), almost no chatter around 1000 RPM, and pretty much no chatter up at 3850 RPM.

1/4" dia carbide end mill
2 flute ?
length and amount sticking out of collet?
coolant ??
suggested parameters
for 3/4" long / sticking out of collet 2 flute carbide end mill on 304 SS
by the way 304 can be bought annealed or still hard from rolling, shearing, etc...... this of course makes the metal 2-3 times harder to machine.
assuming hard 304
120 sfpm
flood coolant
1800 rpm
feed 8 ipm max
max depth of cut 0.045" full width (slotting at shallow depths)
no coolant and chip stick to flutes and take chunks of carbide out of cutting edge assuming chips do not just clog flutes
.... this will take about 0.3hp and create about 84 lbs of cutting force. if metal is thin and vibrating this can damage end mill too.
..... i have seen fully hard tool steel at 65 rockwell C end milled relatively easily and for hours at 300 sfpm and 0.020" depth of cut and flood coolant. In general the harder the metal the lower the depth of cut. I would watch for chips sticking to the flutes when end milling 304 SS. in deep slots if no coolant and a high depth of cut and low feed the heat has no where to go. i find sometimes a light depth of cut and higher feed and even sometimes higher sfpm with coolant works. how this came about is end milling too close and cutting into hard vise jaws. if depth of cut was <0.020" with flood coolant sometimes it does not even make unusual noise and program finishes run cutting into hard vise jaws.

[mflux_gamblej]

1/4" dia carbide end mill
2 flute ?
length and amount sticking out of collet?
coolant ??
suggested parameters
for 3/4" long / sticking out of collet 2 flute carbide end mill on 304 SS
by the way 304 can be bought annealed or still hard from rolling, shearing, etc...... this of course makes the metal 2-3 times harder to machine.
assuming hard 304
120 sfpm
flood coolant
1800 rpm
feed 8 ipm max
max depth of cut 0.045" full width (slotting at shallow depths)
no coolant and chip stick to flutes and take chunks of carbide out of cutting edge assuming chips do not just clog flutes
.... this will take about 0.3hp and create about 84 lbs of cutting force. if metal is thin and vibrating this can damage end mill too.
..... i have seen fully hard tool steel at 65 rockwell C end milled relatively easily and for hours at 300 sfpm and 0.020" depth of cut and flood coolant. In general the harder the metal the lower the depth of cut. I would watch for chips sticking to the flutes when end milling 304 SS. in deep slots if no coolant and a high depth of cut and low feed the heat has no where to go. i find sometimes a light depth of cut and higher feed and even sometimes higher sfpm with coolant works. how this came about is end milling too close and cutting into hard vise jaws. if depth of cut was <0.020" with flood coolant sometimes it does not even make unusual noise and program finishes run cutting into hard vise jaws.

Much appreciated.

My conditions are around .75" down from collet, flood coolant, 0.035" depth of cut. Ive been talking with a guy that has beem running 304 all his life and he says my speeds were way too high too. He says he will run only 500 rpm on a half inch endmill and cut through 304 at reasonable feeds all day.

My other friend who wrote up his settings uses a new haas with high pressure coolant.

I also believe that the tools are being ruined on the first cut after a plunge. I need to find a way to slow the feed down during those cuts.