Speeds & Feeds

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Ok, I do not get it.  How the heck do you calculate how fast to cut, turn
feed, etc.  I've been trying tables and formulas and basically just
destroying stuff before tackling each project.

I've read a dozen pages on-line and read some of the responses here in the
archives and I think there is a fundamental concept or group of constants
that every person who knows how to do it assumes everybody else already
knows when they explain it.

How do you calculate how fast to feed for a particular end mill?

Example, (CNC MILL)
Material = aluminum
Mill = .0625 (2 teeth carbide / could use tin coated or hss if it would work
Radial depth of cut = ????
Axial Depth of cut = ????
Spindle Speed = ????
Feed Rate = ????

Limitations of the mill.
Max RPM = 10,000 (Five speeds.  More if I do not mind hanging the pulleys
part way off the shaft)
Max Plunge Rate = 10 (Z) ((Axis hangs if you try to go any faster)
Max Feed Rate = 20 (X,Y) (Could probably go 30 as long as load was minimal)
Holding Force of Stepper Motors = 280 ozs.

The idea is to find the fastest way to cut a pocket  or du carving without
breaking end mills, dulling them before the job is done, or having the
machine bog down against axial forces.  How can I plug in data like that to
figure out what is going to work best.  I'm tired of ruining work pieces and
breaking mills to find out.

Then how do I plug in that data to calculate the same for a smaller or
larger end mill?

With coolant?

Without coolant?


Re: Speeds & Feeds

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I *think* bottlebob mentioned something like 3% max of diameter per edge iirc.

I googled.

Down in the link, search on 3% you will see bob indicate 1-3% of diameter as
infeed per
flute.  I'd go with that.  Bob removed metal for a living.  He knows his stuff
and forwards.  


Re: Speeds & Feeds


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Basically it is called experience :-)

But seriously, perhaps you should redesign the parts or consider a
different method of making the item.

It sounds as though you are carving something out of a giant block of
stuff - sort of cutting the boulder down until you have removed all
the parts that aren't a horse, as the sculptor said when asked how to
carve a horse... Perhaps that is not the best method.

For example: If one were milling a recess in an aluminum block one
might drill out much of the area with a twist drill before putting the
part in the machine; then the milling would consist of simply
machining to the final dimension.

Probably the major problems in shop work are concerned with either
"how am I going to hold this" or "how can I do this within the
capacity of my machine", rather then how to drive the machine.



Re: Speeds & Feeds

Have you checked the feeds & speeds section of Machinery's Handbook?

If that is hard for you to understand, you might want something like ME
Consultant Pro:


It calculate the speed and feed for various types of cutting tools and
materials plus a bunch of other useful info.


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Re: Speeds & Feeds

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With an end mill that small you absolutely have to have some liquid to
wash away the chips! Any coolant will keep the chips from welding to
the cutting edge ofthe end mill. I am sure this is your problem! Your
end mills are probably not getting dull, just welded over with


Re: Speeds & Feeds

On Sat, 16 Jan 2010 10:43:26 -0800 (PST), " snipped-for-privacy@coinet.com"

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Comeon guys...google is your friend

Total search time for me was 11 seconds..which included typing in the
words "milling speeds and feeds"

Geeze...there are another 50,000 hits ......


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