How to cut
304 Stainless Steel
Machining 304 Stainless Steel: Feeds & Speeds WW167
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hi folks 304 stainless it's a material
that has a notorious reputation for
being difficult to machine or rather
easy to destroy end mills with let's
walk through some speeds and feeds for
both external features as well as some
internal pockets and drilling welcome to
our Wednesday widget
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in Wednesday widget 164 we covered
speeds and feeds for aluminum and
regular or mild steel both of those
materials they're relatively forgiving
they're relatively free machining
there's a wider range of speeds and
feeds that will work and they're not too
particular about what type of end Miller
tool that you use 304 stainless or many
of the same a series are the exact
opposite you've got a more narrow range
of speeds and fees the materials less
forgiving or it can work harden on you
and you've got to be much more conscious
of the tools that you use we're using in
fact a completely different end mill
when we're doing outside features versus
the tool that we use when we've got to
interpolate in to an inside pocket and a
shout-out to Tyson lamb Tyson's got a
great Instagram page where he makes a
lot of golf related accessories as well
as lamb crafted comm where he makes some
incredible putters and ball markers and
golf doughnuts and divot tool repairs
really cool stuff and Tyson has become
really good at machined stainless so he
was really helpful in some of the tips
and tricks and I want to show you guys
it's not that hard we can totally do
this we're using this five flute end
mill from lakeshore let's show the
speeds and feeds and the cuts and then
we'll come back afterwards and we'll
talk about the tools that we're using
why we're using them in some of the
additional details
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first we'll start with the outside
profile we'll do a 2d adaptive first 200
service feet per minute mm of an inch
feed per tooth that's about point zero
five millimeters 0.05 inch that spent
1.3 millimeters or 20% of the tools and
our optimal load we're leaving 20
thousands of an inch or about half a
millimeter as well one of the big
differences with this 2d adaptive plus
2d con to a recipe is in the 2d adaptive
I normally don't leave as much radial
stock to leave but I want to leave
enough here that the tool can dig
underneath the 304 skin which can often
work harden and is something where
you're just not going to be able to take
just like we talked about in Wednesday
widget 164 you can't take little one
foul on stainless it will devastate your
tools quite quickly and finally a 2d
contour same recipe on the cleanup 200
surface feet 2001 foul of the floor just
to avoid rubbing along that floor
switching over to internal pockets so
totally different strategy what's
interesting to me is we're going
actually against the recommendation of
even lakeshore here and I say that only
because that's one of the things when
you get into these materials is you have
to figure out what simply works for you
so I wanted to do two things I want to
give you guys a starting recipe just to
run with but also the kind of confidence
to start thinking about this on your own
so we're using a for flute regular
variable food EndNote so that's not
their stainless style and it's for
flutes instead of five boots again we'll
come back to more about that in a minute
225 Service feet only one thousandth of
an inch per tooth a reduced optimal load
in this case is only 10% of the tool
diameter or point zero to five max
roughing step down of 0.15 inches 15
valve radial stock to leave and max to
degree helix
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let's take a look under a microscope at
these chips we've got an aluminum chip a
mild steel chip and then the 304
stainless chip you take a look at the
aluminum chip you can see how the
material appears to be almost like it's
slightly torn it doesn't have that
really crisp it cut we look at the mild
steel it does have pretty clean shear
lines and then if we go to the stainless
chip it appears to have similarities
back to that aluminum where it's
slightly gummy there's a slight amount
of it just doesn't want to shear as
cleanly as that mild steel now let's
drill 304 stainless first off we need to
spot drill it 75 or so surface
feet-per-minute we're going 3,000 and
we're going down negative 30,000 this is
really important because this is going
to be what sort of breaks through that
hardened skin of the stainless steel and
presents a better non-work hardened
surface for our drill to do its job then
we're drilling 3/16 drill
it's cobalt we'll come back to that in a
second 45 surface feets per minute 3000
we're taking pretty big Peck depths
bigger than I would normally go in this
case just shy of 1 times diameter so
it's a point 1 875 drill about four
point seven millimeters and we're
pecking about that same amount worked
great which gets me really really
excited and I really can appreciate
Tyson he was spot-on and here was his
advice cobalt is the way to go for
drilling 304 it's great because it's
actually pretty darn inexpensive the
drill bit we just use is from McMaster
for 3 dollars and 67 cents that's a very
inexpensive for it for what the task is
at hand
45 service feet per minute 3000 we just
mentioned that full or big peck depth
that's what's really important here if
you take small pecks what you're
possibly doing is exposing the drill to
more of a work hardened surface here's
the other funny thing to walter COBOL
type drills from Lowe's or Home Depot
can work as well for example this guy
off Amazon 20 bucks but for a pack of 12
135-degree tip is what you want stay
away from the drills that have this sort
of branded thing they think they call it
pilot point you don't want to use those
so that's the good news you can probably
even find these drills locally we've
never bought a drill for another reason
I in this for the CNC shop at a home
depot or lowes however you are going to
need a spot drill to Center drill it
that has equal or bigger angle and I
actually didn't have one of those laying
around the shop so we went on to
McMaster and purchased this link in the
video description 140 degree carbide
spotting drill should last a pretty
darned a long time another important tip
is make sure your first Peck isn't a
shallow Peck what do I mean by that
take a look at a wireframe view we're
coming in and we're spot drilling down
to that depth and then we are doing our
Peck 0.16 inch deep but if you look at
my height stab the top height is a hole
top in the feed height I mean where do
we start drilling we don't start
drilling at the top of the hole we have
to start drilling or transitioning from
this yellow rapid move to a green drill
move in this case I set it at 20,000 the
top hole if we watch a simulation peck
peck peck peck peck back up so see that
first Peck was deep a bad example would
be if in our Heights tab we had done
something like change the top height to
have a point one inch offset we're gonna
Peck in point one six depths but we're
raising the top of our hole this way so
what can happen is that first Peck
doesn't go very deep or deep at all and
that can instantly fry a drill couple
final tips if you're going smaller than
1/8 of an inch
don't use cobalt but rather use carbide
the good news is the car by drills are
less expensive in those smaller
diameters and then just be careful with
really thin sheet stainless or sheet
because you've got a skin on both the
top and the bottom then stuff is more
skin relative to the overall thickness
so it's actually more difficult to drill
and so you may be better off
interpolating it quick recap we've got
two different quarter-inch end mills the
five flute four stainless we recommend
for outside profiling or cleaning up
don't ramp in with it here's the link
and here are the basic speeds and feeds
and we have the four flute quarter-inch
this even though it's not technically
meant for stainless we've had great luck
with it as has Tyson use it for internal
pockets or when you've got a ramp into
something and here are your starting
fees and speeds so let's talk a little
bit more about these two tools and
what's interesting so when I go to
lakeshore comm and I click on carbide
end mills
I've got variable for flute for tool
steel
I've got variable v flute for stainless
and mild so what's the difference
between these two well the most obvious
difference is this is for flutes and
this is five flutes but these tools are
actually very different and that the
biggest difference is this four flute
has a more of a honed edge so it has a
more blunt edge what that means it is a
stronger edge because it's actually
honed over but what that also means is
you generally need to increase your chip
load per tooth remember again back to
the speeds and feeds in widget 164 this
inch per tooth because it's a honed edge
or has less sharpness we need to
increase that inch per tooth so as it
engages that material that more honed
edge is still able to dig underneath and
not rub the variable v flute for
stainless has a much sharper edge which
is really good for stainless steel
because believe it or not stainless
steel is kind of like aluminum it's
actually a gummy material it doesn't
really like to be cut so you need to use
a sharper edge to shear it so we use
that v flute for these external features
we found this to be really reliable and
really great the problem with the v
flute is it doesn't like to ramp that's
the red helical lead into a blind pocket
and the biggest reason that doesn't like
to do that is only
one of those five flutes actually goes
all the way to the center of the face so
in some respects you're only cutting
with one flute as you're doing an
interpolation and there's very little
gash clearance which is ability on the
face of that tool to evacuate or cut the
chip so you could adjust the helical
ramp diameter to try to work around that
but the better answer and again shout
out to Tyson for the help years just use
the four flutes
yes it's technically in the title not
meant for stainless in the description
includes stainless steels and I'll admit
as a layman this sometimes is
frustrating but as you get into these
more exotic materials you've got to use
recipes that your tooling supplier or
people who have done this before work
and if it works awesome some other tips
and tricks when you do a helical ramp in
never use more than two degree Rankine
again we recommend and Tyson recommended
using the four flute instead of the five
flute don't go greater than up 3/16 inch
or about four point seven millimeter
depth of cut I reduced this one to 0.15
because it's a point three deep pocket
so just taking it half at a time you
absolutely need an air-blast to help
evacuate the chip the number one cause
of end mill failure and stainless is
recutting your chips
you also need coolant for the lubricity
to help avoid the chips sticking to the
end mill so that's why I like the fog
Buster here with the air pressure and
some of the quality chem mixed into it
flood coolant it would work as long as
it's high enough pressure to really
evacuate those chips start off with a
reduced optimal load here we're doing
10% you can increase that but start with
something that works and then start
increasing your way up and experimenting
again ramp with a four flute once you're
ramped in you can go ahead and finish
with a five flute because again once
you've done that helical interpolation
the fact that it's an inside pocket is
no different really than the outside
pocket tools that have a small corner
radius in this case it may only be ten
fifteen twenty thousand seven-inch can
really help increase your tool life
because the very tip of that flute is
the weakest part so by getting rid of
that weakest
by adding a radius you're really helping
extend your tool life and avoid shallow
pockets because stainless steel has a
work-hardened scale when you purchase it
if you try to take say a ten or fifteen
thousand in all work-hardened some
material so if you have to do that
you're better off decking it off first
and so long as you have good feeds and
speeds when you do that you shouldn't
rework harden that service at least
that's my understanding we're gonna do
some more experimenting because quite
frankly this is pretty fun and it's good
to push myself
we tried machining three or four years
back and we failed so quickly that I
gave up you know it's intimidating I
think it's something where I'm hoping
giving you guys the right recipe the
right speeds and feeds the right tooling
we can all be cut in three or four folks
hope you learn something hope you
enjoyed take care see you next Wednesday
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