Re: Any "Best Practice" Recommendations for clearing chips and feed/speed when cutting Aluminum??

Howdy, yethdear here again;

Welcome to the wonderful world of machining metal. EWWWWWW! Don't use
WD40, yes this flammable and you are risking a lot using it for
machining. Here are some suggestions for you.

Purchase a small air compressor and tank for about $100. Then plumb
up an air cooling system using 1/8" copper tubing. Make an air blast
nozzle that is attached to you machine so that it supplies a constant
flow of air to your cutter at all times. This will cool your cutter
and blast away the chips too.

Go to www.use-enco.com, they have a variety of spray mist systems
that you can buy. These work good but they are messy and pose health
problems if you use them in a confined area. Enco also has a variety
of cutting fluids and oils that you can buy in small quantities. Some
of these can be mixed with water or used full strength. I usually
pour some in a spray bottle and then apply a squirt now and then as
you need it when machining. They also have a variety of cutting
fluids and tapping fluids that come in a squirt bottle.

I sometimes use old motor oil. It works good as far as lubricating
but can smoke quite a bit. I just apply it with a brush. No matter
what, you are going to have some mess. This is not a hobby or career
for a neat freak. I'll usually try to keep the chips out of the path
of the cutter as much as possible. Then I usually wait till I'm done
with a project and do a thorough job of cleaning up. One advantage to
cutting fluids and oils, it keeps the rust away from your machine.
You'll just have to live with mess. ALSO…..ALWAYS WEAR YOUR SAFETY
GLASSES!!!!

A friend of mine says he uses Windex as a coolant for aluminum. I
don't know about the ammonia though.

As for speeds and feeds. This is not an exact science. The numbers
you'll find are "ballpark" at best. RPM is based on the type of
cutter you are using and the type of material you are cutting. For
high speed steel cutters on aluminum, a published "cutting speed"
value is around 400sfm. For steel, it is 100sfm. Now here is a
formula for determining RPM;

(CS X 3.8) / cutter diameter

Here is how this works using aluminum and your 1/8" endmill

(400sfm X 3.8) / .125 = 12,160RPM

I take it that this is probably too fast for your machine. That's
okay, it's telling you to run this cutter as fast as you can.

Now for feed, this is based on the recommended chip load per flute
for your size of cutter. By experience, for an 1/8" endmill, I would
figure .0003-.0005 per flute. This is the amount of material that
each flute of your cutter removes for each revolution. Here is how
this works.

FEED = Chip load per flute X RPM X number of flutes

Using what I'm guessing is your top RPM on your machine

FEED = .0005 X 3500 X 2 flutes = 3.5ipm

Now, where to get all these recommended values. The best place is a
book called "The Machinery's Handbook" This is also available through
www.use-enco.com. I know I sound like I work for Enco…I don't it's
just a great place to get all this stuff. The handbook is the bible
for machining. It has ALL the information you need if you're serious
about machining. The book is about $65 but is well worth it. You can
also find it at your local book stores in the technical section. Just
look in the index for speeds and feeds.

You can also find published values on the web. Search for "speeds and
feeds" for aluminum" or whatever material or cutter type you are
using.

Another good place for info, my web page. I am currently working on a
database program that calculates speeds and feeds for various cutters
and materials. Once I finish it, I will make it available from my web
page at http://www.geocities.com/yethdear0/
There will also be more useful information posted there as time goes
by. Excuse the ongoing construction on it.

REMEMBER…speeds and feeds are not exact. Most of the time you will
have to adjust them as you are machining. RULE OF THUMB..if your
cutter is screaming and chattering, you are not feeding enough.
Increase your feed rate or slow down the RPM. Make your cutter CUT
more. Not too much though, or you will take too big of a bite and
snap your cutter. You can also break cutters by not keeping enough
cutting fluid on it and it heats up and the aluminum will weld to
your cutter. You can also break cutters by not feeding enough. If it
is screaming and chattering, the cutter will beat itself to death and
knock the sharp edge off of the flutes. Now you have a dull cutter.

Another RULE OF THUMB… the smaller the cutter the faster your RPM.
BUT the smaller your chip load will be. (Fast speed….light cut)

It all comes with experience, don't give up and be patient and have
fun playing with your set up.

Let me know what your results are.

yethdear

--- In CAD_CAM_EDM_DRO@y..., glee@i... wrote:
>
> Well, tonight I switched from cutting wood to machining 6061
aluminum with
> my Sherline Mill using a 1/8" end Mill to Mill a part 1" x 1.6"
by .25"
>
> It was an education to say the least. In the process of documenting
the
> results, I arrived at some questions:
>
> When I was practicing on plastic and wood, I ran the ShopVac with
the
> intake nozzle next to the cutter. This way, it was a superbly clean
> process.
>
> When cutting aluminum, I used WD40 From time to time to lubricate
the
> cutter. I noticed that the WD40 label says "Highly Flammable -
propane." I
> decided that I would not use the ShopVac and the WD40 at the same
time for
> fear of starting a fire inside my ShopVac and making my ShopVac a
flame
> throwing jet engine. (Am I correct in this concern)
>
> Since I was no longer using the ShopVac I now had a micro chip
problem.
> This was further complicated by the WD40 (used in moderation) and
resulted
> in an aluminum "Slurry" surrounding the cutter and resting on top
of the
> part.
>
> No problem, I thought. I used an acid brush to brush away the
debris -
> still wishing I could run my ShopVac.
>
> Well, combine the above with the lessons I learned about climb vs
> conventional milling as well as and feed/speed rates, I have
probably
> broken many rules tonight not to mention possibly destroying my
cutter. At
> least I am learning and having fun while making chips.
>
> So, now that I have shared the gory details, I will ask for
> feedback/correction:
>
> 1. Any ideas on the removal of chips
>
> 2. Any ideas on the lubrication of the cutter (It's an 1/8" end
mill)
>
> 3. I experimented with feed rates and speeds as I was encouraged to
do. I
> came up with 2500 rpm, 5-10" ipm on XY and 1 ipm on Z seemed to
work. I
> would welcome some recommended rates for my sample part
>
> Spindle Speed?
> Feed Rate XY?
> Feed Rate Z?
>
> This is a learning adventure for me. I'm open to all kinds of
feedback so
> fire away :-)
>
> Thanks. I cant wait to check my email in the AM to see what kind of
> responses I get....
>
>
> Eric Mack
> glee@i...
>
>
> P.S. I am documenting my adventure to try and write a tutorial to
help some
> future lost soul do this. For now, I return to wood and plastic for
> practice until I master the speed/feed stuff.