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Cutting tools for micro milling machines


#1

Thanks to all those who offered names of suppliers after my last
request. Unfortunately, I couldn’t find the type of cutting tool
that I require. Maybe they don’t exist commercially. The cutting
tools I see available are useless for most of the work I do. If the
width of cut is small, the depth of cut is also small. I need
cutting bits that have very long depth of cut compared to width of
cut. For example, for a witdth of cut of say 0 .4 mm. , I want a
depth of cut of say 5.0 or more. For a 1.0 mm width of cut, I want
a depth of cut of 15 mm. or more. I make these bits but they are
crude and it’s a pain in the butt to cut them. I’ve tried using
twist drills but they are not efficient cutters when run laterally
even in wax.

I make these cutters using a flex shaft machine to hold a H.S. burr
and mill it down to the desired diameter using another flex shaft
machine , sanding discs and cut-off discs. Once milled to the
desired diameter, I grind the shaft down to exactly half it’s
thickness for the cutting length I want and then grind a 45 degree
angle on the leading edge. These work very well although you have to
watch the speed of the machine or they will easily snap off. The
greatest problem with these cutters, other than the difficulty of
fabricating them by hand and eye, is that I find it impossible to
make them with a consistent width of cut. Each time i break one I
have to cut a test square and recalibrate them. If I use one to cut
the seat for a bezel set stone for example, and break the bit, I not
only have to make a new bit but also have to go back to my design
program and change everything to accomodate the new width of the
cutter.

I have a forth axis on my milling machine so I know I could use the
machine to grind the tools more accurately but this is not an option
I want to persue. I ruined my last machine this way. The grit from
the sanding discs got into everything.

So, my question is this. Are milling cutters with very tiny width of
cut and very long depth of cut commercially available? If so, from
where?

R. Hood


#2

R. Hood The length of the average cutter is based on the formula of
cut depth equals 3 times the diameter. The shear strength of a column
beyond that height becomes very easy to break. You can have cutters or
end mills made but they are very expensive. An example is a 1 mm end
mill I had made with a 7.5 mm cut length for $142.00 seven years ago.
You may find that it is easier to drill holes and add wires after,
or have the parts printed by a service bureau like M2 systems. David


#3

Mr Hood, The cutters you are looking for will not be found at the
usual engraving cutter suppliers. You need to step up to companies
such as Data Flutes and International Mini Cut. These guys have
specialised tooling for the Electrode industry and therefore cutting
into graphite, the extra lengths do not pose the problem of
resistance to these extended lengths as they would in metal. Using
these extended lengths, you will have to pay attention to your
machining strategies, because even in wax, a long tool can flex and
cause run out which will result in chatter along the profiled
surface. If you need help, give me a call. Best Regards. Neil George
954-572-5829


#4

Mr. Hood: I do not have a computerized milling machine, but I do use
an old Gorton 2 dimensional industrial engraving machine (1940’s
Model 3U) to engrave simple metal molds and other jobs that come up.
With the use of a small cutter grinder I produce very small single
lip cutters with varying cutter geometry depending upon the material
to be cut and the job to be done. I use carbide cutter blanks that
are pre-ground to their center line which are available from
Geisswein. I would imagine that these same cutters would work on
computerized machines.

I use a small handheld microscope with a measurement scale on it to
guide me in preparing the cutter width. The smallest cutting point I
work with is .005" across the point. I suppose smaller is possible
but not necessary for my work. These points can also be made in a
bullnose configuration for a rounded bottom cut. These points also
cut deeply and when ground properly not only cut across the face of
the point but also along the side of the cutter. Of course to use
fine cutting points the cutter has to taper down to the point. For
engraving with small cutting points like these I use the maximum
speed on my machine of about 20,000 rpm

These cutters are available custom made by companies listed in
engraving journals. I have a setup to make my own because they break
easily and sometimes I need a special point quickly.

So it sounds like what you are looking for is a cutter grinder for
single lip cutters or one of the suppliers listed in the engraving
journals. Gorton makes a good one that can be found used (search the
internet) or new and there are also Chinese knockoffs (don’t know
about quality). I have an old Preis (no longer made) cutter grinder
that is a scaled down version of the larger Gorton. Personally I
would rather have the larger grinder, but the small Preis does a fine
and accurate job.

With technology it is not always the cutting edge that changes, but
what drives it.

Ken Gastineau
Berea, Kentucky