I have to mill a profile out of 1/8" sheet brass, exact composition
unknown. It isn't very hard, though. This will be entirely edge
milling i.e. milling with the side of the end mill. I very rarely
mill brass and I'm unfamiliar with its machining properties. For
side milling of brass sheet stock should I just use any 4-flute
end mill, or is some special topology highly desirable?
Just use a sharp one. You do know about brass being 'hungry'? If you
have no size restriction, like for inside corner radii, use somehting
fom .187 to .312 diameter. I like standard 3 flute for something like
this, but a 2 or 4 will be fine. Standard helix, and a light spray of
water soluble coolant, though most will say run it dry. The spray will
blow chips away, helps with visuals.
I have always heard that brass likes to be drilled with a drill bit
with no rake on the leading edge. If the bit has rake, the bit wants
to screw itself into the brass. I have always ground the leading edge
off my drill bits (the leading rake angle is parallel to the length of
the drill) when drilling brass, with remarkably better results than
the factory points.
Sooo...With this in mind, I would grind the leading edge of the
milling cutter to a zero rake, i.e. parallel to a line through the
center of rotation. This should keep the cutter from grabbing and
trying to feed itself into the work, resulting in a more accurate cut.
I have never milled a piece of brass this thin, and would be
interested in what you discover in the process.
Brass mills easily, just use a real sharp cutter.
Your problem here will be clamping. 1/8 stock will want to pull up and
chatter. I'd suggest you make a brass sandwich. Sacrificial material above
and below, clamp it all to the table.
I also make a sacrificial sandwich for this type of work, out of plywood.
With planning, screws can be used to hold the sheet in place in certain
areas of your pattern. If the shape is irregular, and doesn't have to be oh
so precise, I draw the design onto the plywood and mill away at the
"sandwich". I have a 4" wide bar stock that has been milled to a "T" shape
of end profile, tapped through vith various sized holes, that I clamp into
the mill vise for this type of flat work. Bolts, or a toolmakers clamp or
two will allow you to turn the work as necessary to whittle away at it. It's
one of the handiest milling accessories that I use.
I'm making a special-purpose workholding jig just to do this profile
milling on the rotary table. There are two holes in the part and I'm
planning to use them to hold the part down with. Unfortunately I'm going
to have to use #10 SHCS to do the holding, but it's only 1/8" brass and
I'll take it easy on the milling. I have to make several of these parts
and this seems to be the only way. The work will be supported on steel
bushings below (just smaller than the profile) and clamping washers
above (also just smaller than the profile) so it's already sort of a
It's my first attempt at making a jewelry-type item, we'll see how it goes.
I machine a lot of brass. Sheet, round, hex, and square bar etc.. Your
sheet may be half hard brass or it may be soft. Half hard machines
best. The soft brass will be gummy. And making a conventional cut will
show this rapidly as the chips tend to stick to the cutter and get
pressed back onto the work. Use either a two or four flute cutter. If
your set up allows climb cutting is best. Use a non sulfurised cutting
oil. The sulfur stains the brass. Water soluble oils without chlorine
work great. Use 300 to 350 sfpm with HSS tools. The brass can be
routed easily. So, if the contour tolerance allows you might want to
consider making a template and routing it. Drilling half hard brass
with a regular drill risks having the material pull the drill into it.
Especially if you are enlarging a hole or drilling after center
drilling. Stoning a drill like one made for drilling plastic helps to
avoid this. Brass cuts so easily you will love it. If you have a
choice when buying the brass get the half hard. If you will be milling
pockets, even one that's quite shallow (.010) the half hard sheet will
warp. Just milling a contour on the oustide will not cause this major
warping though. If you use a 1/2" dia. cutter you can stack the sheets
up 8 at a time and cut them all at once. Clamping well of course. If
you can, make your setup so it is possible to add clamps and remove
others so the part can be milled all around in one clamping. The half
hard brass will make sharp chips that are like needles so watch out.
Eric R Snow,
E T Precision Machine
All of the information you have received is good, but the less helix
with either the drill or the endmill, the better.... Soft brass is
very gummy and will tend to chip weld... a very light cutting oil may
be in order if this is the case. Chip welding will destroy any
surface finish you were hoping to get.
I do edge mill sheet brass.
If thick enough to not bend you can use spiral flute mills.
If there is a chance that it will bend use straight flute mills or in an
emergency use a reamer as a mill.
Watch for buildup of chips that clog the flutes.