A customer was looking for an end mil to try on plastics. Plastics come is a wide variety of compositions and hardness, therefore a lot depends on the type of plastic being machined. Here is our advice to get started:
All of our end mills are
designed primarily for metals, but many people use them on plastics, composites
and hardwoods as well. I would start with the basic four flute end mills. If
you have trouble with chip clearance/chip evacuation, you might have to look at
a 2 flute, however, you will get a better finish with the four flute. We have
some customers that have used the end mills for aluminum in harder plastics.
These tools for aluminum have a higher helix angle and more room between the
flutes for chip evacuation. Because the core does not have to be as large and
strong as for other metals, we can grind these deeper for better chip removal.
The aluminum cutting are a high-performance tool that cost a lot more than the
regular end mills though, so you have to take that into account.
Although you may see some
benefit from a coating, I don't think it would justify the expense, so I would
stick with the uncoated tools. Most people cutting plastic seem to be using
uncoated tools. I don't think you see much benefit from the coatings until you
reach higher temperatures, like 900-2200 degrees F.
So here are some links to
some basic ones to consider. Other variables are length, ball end and corner
radius, in addition to the regular length square end end mills that I have linked to
Just let me know if we
can be of any further assistance.
A customer was trying to decide whether to use a 2-flute or 4-flute carbide end mill for his job on aluminum. One important question before spending the extra money for a high-performance tool, is how many parts are you making?
I think one you
might look at is our part number 136475. This is 1/4" x 4" long with
a 1" length of cut. The number of flutes is a trade-off between better
finish and better chip evacuation. Sometimes with softer grades of aluminum the
flutes could get clogged up, but as long as that is not an issue for you a 4
flute will give you a better finish and do more work per rotation of the tool. I
think a lot of people are using this tool for doing a similar application. There
is also a popular one with the gunsmiths that is specifically for aluminum. The
part number is 150104 (150027 for uncoated). This is a high-performance tool
that is capable of doing long production runs and much high speeds & feeds
than the standard tool, but if you are not doing a large quantity it would
probably be more than you need. The high performance ones have 3 flutes, a
deeper clearance between the flutes for better chip evacuation and an optional
ZrN coating specifically for aluminum and other non-ferrous metals. The
high-performance also has a 45 degree helix instead of the standard 30 degree.
This provides a better finish due to a shearing action of the flutes and also helps
get the chips up and out. The main reason carbide end mills fail is when the
re-cut a chip from the previous machining, so the chip evacuation is important,
but if you are doing a smaller quantity you can try to use air of fluids to
keep the cutting area clear from chips.
We recently had a question about milling fine patterns in 92% copper, 8% nickel coin. The user would like to mill through to the other side of the coin and create a pattern with finely detailed edges.
Yes, this definitely can be done. You generally are able to mill at a
max of 1Xs the diameter of the tool. So it is a trade-off between the diameter
you will need for the finer details of your design and the number of passes you
will need to make to go through the material. The micro end mills are available
with lengths of cut that are 1.5Xs and 3Xs the diameter. The type of mill you
use would depend on the diameter you choose and what operation. The more flute
the better your finish will be and the more cutting action per rotation of the
tool you will get, however if the material is mostly copper, that may clog the
flutes and require a 2 flute for the roughing portion of the operation.
Ideally, if you can find a diameter that will allow you to do the whole pattern
without a tool change, that would be nice, however you may have better results
doing it in two steps. Maybe use a larger 2-flute tool to allow a complete cut-through
to the other side, and then rough out the bulk of the pattern. Then you could
follow-up with a smaller diameter 4 flute tool that will allow you to finish
the detail. If you do the whole thing with a very small tool, it may take
awhile. You want to keep the tool/flutes as short as possible to improve
rigidity, however you need some room for chip evacuation. As with everything in
the milling process, it is a trade-off between a few different variables.
As far as the speeds and feeds, we have all of that information
available at the links below. An easy way to do it is to plug the values from
the chart into the online calculator. One variable you won't know is the
limitations of the spindle speed of the machine you decide to purchase. Which
brings me to my next point.
We don't really have a recommendation for a particular machine, but I
know there is a huge range of options out there. I believe you will want to run
these smaller tools run at higher RPMs, so that might be a factor. If you plug the
variables from the speed and feed chart into the calculator, that will fill in
a spindle speed you could use as a reference. One of the brands that has been
around for awhile for smaller work like this is Sherline. http://www.sherline.com/
Please see the point-by-point answers per your list below. Also, here is
the link to the speed and feed chart and calculator. Just let me know how else
we can help you move forward with your project.
Thank you for
Speeds & Feeds: http://www.kodiakcuttingtools.com/CarbideEndMillSpeedsAndFeeds.asp
Online Milling Speed & Feed Calculator: