On 12/8/2017 1:02 PM, Bob La Londe wrote:
I never thought I'd be doing this sort of work ever.Â* I am quite content
to high speed micro mill aluminum.Â* When I was first learning I asked a
lot of questions here and elsewhere.Â* Eventually I put together enough
information to where I can produce satisfactory results most of the time.

When I say micro milling I mean optimizing cut rates with modestly high
speed spindles (24K RPM) and pretty small cutters.Â* Almost no milling
job that I do gets by without a finish pass without atleast a .0625 ball
mill.Â* Quite often I have to use .03125 ball mills to finish some
details.Â* I even have to break out the .0156 stuff once in a while.
That's the range I am talking about when I say micro milling.

For all of that work I use uncoated square end and ball end mills with
6-8% SC520 and water with a constant flood.Â* Cutters last a very long
time and the results are good.Â* Jobs often last for hours.Â* Sometimes a
single tiny little cutter has to work for hours.

Well somebody offered me enough money to tempt me to do some similar
work in 4140HT.Â* I've milled some hardened steels and hard tool steels
before.Â* The numbers say 4140HT should be easier.Â* Its a sort of
compromise.Â* My past experience shows me that a low speed and feed with
an AlTin or TiAlN coated cutter works pretty good.Â* That's fine when you
are pushing a 1/2" 5 flute end mill, but I have to do some of that small
detail work to finish this job.Â* I need to push the envelope with ball
mills as small as .0156 for some of the finish work.Â* I can break it out
so I don't have to finish everything with it, but its still going to
more time than just a few hours.Â* HSM Adviser gives some numbers that
show days instead of weeks, but I wonder if there is anything I can do
to actually get those numbers.Â* With aluminum heat and thermal shock is
not really an issue.Â* With Altin in steal I don't run coolant, but I
admit I do throw a little cutting oil on the part.Â* I've just never done
small or micro milling in harder steel.Â* Well, I have engraved some
knife blades, but that's it.

I'm hoping I can cut down the learning curve, but I am prepared to break
some cutters and ruin some work pieces if I have to.Â* Chip clearance is
probably also going to be an issue.Â* Maybe an air blast to blow chips
clear and see what happens.Â* The thing is we are talking about steel.
Steel chips don't blow clear as easily as aluminum chips.

I am open to any suggestions.

Worst comes to worse I am prepared to tie up my machines for a few
weeks.Â* I certainly figure days even in the best case.


Well I just started breaking down stock for this job. I don't know how
its going to micro machines, but regular machining should go just fine
based on the way it saw cuts.