# How Deep With A Face Mill?



## TC0853 (Mar 8, 2016)

Obviously, an indexable face mill is designed with milling a flat surface. So with that being said, even if you're just taking a cut of .010" you're still cutting down into the material. Not having done a whole lot of face milling, what kind of depths can be accomplished with one. No doubt there are a lot of mitigating factors, not the least of which, I'm sure, would the limitations posed by the type and size machine you're using. Any takers on this one anybody? Any info is appreciated!


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## Wreck™Wreck (Mar 8, 2016)

Until it stops working well, then try less.


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## JimDawson (Mar 8, 2016)

I have a 2.5 inch, 3 insert face mill that I have gone 0.150 deep in steel and 0.250 deep in aluminum at the full cutter width, on a 3500#, 3 HP machine.  Don't know it that's recommended, but it works for me.  Probably wasn't doing my spindle bearings any good.


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## Jason Annen (Mar 8, 2016)

I have stopped a 2hp machine before at .150" in steel.  Generally I stay between .050" to .100" on a Bridgeport style machine.

Jason


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## TC0853 (Mar 8, 2016)

That's good to know fellas, thanx! 2 out of 3 isn't too bad.


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## 4GSR (Mar 8, 2016)

For my 645 Index mill, I have two face mills to choose from.  Both cut about 2"to 2-1/2" wide cut.  I generally don't exceed .075" deep.  About all a 1 HP motor will handle cutting 4140HT.

Back in my earlier years, Machines we used to build to spiral drill collars, I would push a 8" face mill with 45 deg. lead, double negative square inserts, taking about 3/8" deep cut at 72" inches per minute on the feed.  50 HP motor never groan.  Boy! did it leave a floor full of chips!


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## TC0853 (Mar 9, 2016)

Well I'm using a Smithy 3 in 1, as they go it's a good one, but I certainly won't be making any cuts like that with 1 1/2 HP, but yeah, I'll bet it did make some chips LOL. I haven't done any plunge cuts with either of my face mills, the inserts are out on the edges, got a 40mm and a 2 1/2", but for example it seems like I can get that 40 to come in from the side at .065" DOC and move along OK. If I go much deeper than that it pretty much doesn't matter how much I slow it down, it's just a little bit more than its comfortable with. I would have dedicated stand alone machines but my shop is out of room.


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## T Bredehoft (Mar 9, 2016)

I remember taking 1/4" passes with a 9" (26 insert) face mill, but the Lucas had a 4" spindle, don't know the HP of the motor. That was really awesome, the inserts had 1/8" wipers and you could advance .050 per cutter per rev. and get a smooth finish in CI.  But you're talking about hobby mills, I guess.


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## Richard White (richardsrelics) (Mar 9, 2016)

Well, here is my input. I do this for a living as well as a hobby, so that means you get 2 answers. Don't worry I will only charge for one.  There are specifics for every tool and every machine, so it is a combination of what tool you use AND in which machine you use it in. 
At work, some would crap to know how heavy of a cut I take, but at work I am there to make money for the boss. So I push the machine to the max, and then add 10%. He smiles at what I can do, and IF by chance something breaks we both agree that it must have been too much, so I change the settings and move on.  At home the same does NOT apply. I do this, yes I really do this to relax at home, so I take nice easy passes, just enough to do it right but never so much to risk the machine.

It all boils down to a few things:
1. Rigidity of the machine.
          How snug are your gibs, are the ways sloppy, is your tool post mediocre at best or is it solid as the rock of Gibraltar?
2. How rigid is your work holding?
          When I was trained, the USN First Class Petty Officer Machinery Repairman had this to say about our setups,
          "If it ain't tight, it ain't right!"
3. Tooling,
           Properly sharpened and setup tooling is key to reducing stress on the machine.
All of these play a roll in how much of a cut you can take.
But ultimately YOU have to figure out what your setup can handle, start off small, .03 or so with a feed rate of .003 per revolution, and go from there.  If you hear no funny noises, grunts and or groans, you win, next time gradually increase your depth of cut. Your feed rate should be in the area of .002 - .005 per revolution, check the quick change gear box, if equipped to find this.

I hope this has helped you, as much as I have enjoyed typing it out.  THIS is the stuff that needs passed down the line from us "OLD" toolmakers.

Doubt you will find any of that in a book.

Take care and good luck

Richard


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## TC0853 (Mar 9, 2016)

No that's fine, the more input the better. Most of what you're saying is pretty much how I'm approaching it, the part about doing it in the home shop that is. I wouldn't even consider trying to push a hobby machine past its limits, whether it was mine or a friend's, if a guy has a half a brain he can tell when the machine is not happy. Oh, and thanx for giving me the bro deal on the advise.


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