# Re: End Milling Strategies

BottleBob wrote:

There is an interesting article in Modern Machine Shop titled "Steering
Clear Of Corner Concerns".

http://www.mmsonline.com/articles/020604.html

To ALL:

The new minimal "TEA" toolpaths from Surfcam seem like they'd be quite
useful.
It's unfortunate that the article seems to have had a couple of
boo-boos in the RPM of cutting 4140 (12,000 RPM), and the feedrate
(1,000 IPM).

Here's another article titled "CAD/CAM Considerations For Micromilling"
in what I believe to be the same issue of MMS that also seems to have a
couple of numerical mistakes.

==========================================================
http://www.mmsonline.com/articles/020603.html

For example, to maintain a cutting feed of 100 meters per minute with a
10-mm cutter, the spindle should rotate at approximately 3,200 rpm. For
a 0.1-mm cutter, the spindle would have to rotate at 320,000 rpm. Such a
high spindle speed currently isn't available. The maximum cutting feed
possible with a 0.1 mm cutter is approximately 15 meters per minute?far
from being considered HSM.
==========================================================

I don't think fluently in metric, so let me roughly translate the
numbers to their English/Imperial equivalents:

100 meters per minute = ~ 3,900 inches per minute.
10 mm dia. = ~ .394" dia.
..1 mm dia. = ~ .004" dia.
15 meters per minute = ~ 585" inches per minute

So what they seem to be saying is that a .394 dia. cutter is being spun
at 3,200 RPM and fed at 3,900 IPM. Assuming a 4 flute cutter I figure
that would be like a chipload of about .305 per tooth. Quite the
healthy chip load there, wouldn't you say? LOL

Also for a .004 dia. cutter and roughly assuming a 30,000 RPM speeder
head, feeding @ 585 IPM would work out to a chipload of something like
..0049" which is larger than the cutter dia! Even a 60,000 RPM speeder
head would give a chipload of something like .0024 which is over half
the cutter dia. A chipload of 15% (which is on the large side), of
cutter dia. for a 4 flute .004" end mill would probably be something in
the (.0006) range.

I like Modern Machine Shop, I don't subscribe, I just come across them
from time to time, and I know they must be under some extreme pressure
and time constraints to get their articles published. However, I think
it might be in their best interests to have a machinist proof read their
articles before they are sent out for printing.

--
BottleBob
.

## Relevant Pages

• Re: End Milling Strategies
... boo-boos in the RPM of cutting 4140, and the feedrate ... 10-mm cutter, the spindle should rotate at approximately 3,200 rpm. ... .0049" which is larger than the cutter dia! ...
(alt.machines.cnc)
• Re: Form tapping blind holes, what coolant?
... RPM, but wanted to keep the chip load the same as it was, I would have ... Using IPR, if I make an RPM change, I don't have to do anything else. ... My feeds stay exactly the same as they were. ... 4-flute cutter, is .002" Per Revolution of said cutter, i.e. the ...
(alt.machines.cnc)
• Re: Better luck machining aluminum
... This time I am using 1200 RPM and 1 IPM, and in addition I use WD-40. ... 4-flute cutter I'd feed at ... I think that part of my problem is that I use a ball endmill. ... one side, and even then, you have to program speeds and feeds carefully ...
(rec.crafts.metalworking)
• Re: Better luck machining aluminum
... This time I am using 1200 RPM and 1 IPM, and in addition I use WD-40. ... 4-flute cutter I'd feed at ... I think that part of my problem is that I use a ball endmill. ... one side, and even then, you have to program speeds and feeds carefully ...
(rec.crafts.metalworking)
• Re: Better luck machining aluminum
... This time I am using 1200 RPM and 1 IPM, and in addition I use WD-40. ... much better to take lighter cuts and keep the cutter ... I think that part of my problem is that I use a ball endmill. ... As for speeds, you can't run an ordinary mill at surface speeds in aluminum ...
(rec.crafts.metalworking)