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Hi just got a bridgeport turret mill, cut a key slot today in a 1 1/4" S/S bar, dont know how fast to expaect it to cut though, i was using a 8mm (3/8ths") carbide 4 flute end mill,920 rpm, 2"/min travel and cut 1mm (1/25th") per pass i want to know if im being hesitant or reckless on what i done today? for using say 3/8ths, 1/2" 1nd 3/4" endmills what should my cut depth, pass rate. and rpm be, prob in 316 Stainless Steel and what differance would machining mils make? just need some guide ,lines, milling is sooo tiresome compared to turning with things spinnin fast and swarf flying in your face,

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With solid carbide, you want to run dry with an air nozzle clearing chips and cooling the cutter constantly. I'd run a bit faster with carbide, maybe 1500rpm. With a mill like that you need to watch out for deflection. Usually cut a little narrower and then finish the two sides. Depth often depends on the length of the cutter, stubbies can run pretty deep, but never more than the diameter of the cutter deep in one pass when plowing. Chips should come off blue, but no more.

Oops, just saw "stainless". Stay with the rpm you have.

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Depends. With milling there are some guidelines, but nothing is set in stone. Factors to consider are material, cutter condition/material/diameter, rigidity of setup, horsepower of machine, tightness of machine, etc. I pretty much use carbide exclusively where I work now. The Acra mill is a Bridgeport copy with a step pulley, and a 2 speed motor. It stays on the second from the top pulley groove for the most part, and I switch between high, and low speed depending on the cutter size.

My old shop teacher told us run it as fast as you can, and as deep as you can till the machine lugs, then back off a little.

With some materials you need to take a deep cut to get a good finish, otherwise it just seems to scrape the metal off. Others prefer climb milling as opposed to standard milling.

So what does all of this mean? Experiment some with different feeds, and speeds to see what works best. The general rule of thumb for carbide is blue chips,and no color change for HSS cutters.

I use cutting oil in certain circumstances to reduce the possibility of chips galling to the workpiece. Smokes like mad when using carbide due to the heat generated, but leaves a nice finish.

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  • 2 weeks later...

I would say a little heavier cut wouldn't any thing. We've got an ancient little vertical mill at work and I can comfortably cut a 5/8" keyway full depth in one pass. Couldn't tell you my speeds and feeds, they're based on how fast the handles are spinning and how many times the one remaining drive lugs hits my thumb in 10 seconds.

As for coolant, I'm with Grant, either flood it or f*ck it. If you can't keep a heavy constant flow going that's guaranteed not to stop don't bother.

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