I get to make a boatload of small accurate parts from 6061 Al, mostly 1/2"
stock. I sooo like Aluminum! I bought a bunch of different size stock bars
from McMaster, they deliver the SAME day, how cool is that! But, squaring
up my sawed pieces with very light cuts in the BP has me a bit confused as
to how I'm getting tiny amounts of swarf that are 'kinda welded on the cut
surface. It seems to scrape off easily. I'm using the side of a new 3/4"
HSS end mill without lube and clamping the pieces in the vise and cranking
the "Y" handle.

Years ago I bought a large amount of Al drops that were some kind of
high-strength aircraft alloy, I don't know what it is but it machines
beautifully and no swarfy-sticky issue. I NEVER though I'd be asking a
speed/feed/lube question but I'm curious as to how I can do this better. Is
the 6061 just softer/gummier? I have 54 more parts to make and as much as I
like doing the work I hate wasting time scraping the parts. I hate cleaning
lube off of them too. Actually, I think I'd much rather just draw the stuff
and have it magically appear on my desk.

On Sat, 25 Aug 2007 02:50:52 GMT, "Tom Gardner"
wrote:

I'm getting tiny amounts of swarf that are 'kinda welded on the cut
surface. It seems to scrape off easily. I'm using the side of a new 3/4"
HSS end mill without lube and clamping the pieces in the vise and cranking
the "Y" handle.

Climb cut the last couple thou, it'll knock the hairs off and leave a
nice finish. Don't spare the RPMs.

--
Ned Simmons

Tom Gardner wrote:
I get to make a boatload of small accurate parts from 6061 Al, mostly 1/2"
stock. I sooo like Aluminum! I bought a bunch of different size stock bars
from McMaster, they deliver the SAME day, how cool is that! But, squaring
up my sawed pieces with very light cuts in the BP has me a bit confused as
to how I'm getting tiny amounts of swarf that are 'kinda welded on the cut
surface. It seems to scrape off easily. I'm using the side of a new 3/4"
HSS end mill without lube and clamping the pieces in the vise and cranking
the "Y" handle.
I can tell you are "conventional milling" it, where the side of
the cutter is moving against the movement of the work. This
causes the cutter tooth to approach the just-cut surface and
skate along it until the pressure develops to the point that it
penetrates the surface and starts to cut. This sliding at the
beginning is indeed welding the chips back onto the just-cut
surface, and is called "chip rewelding" and a number of other
bad words.

The opposite direction is called "climb milling", where the
cutter tooth moves in the same direction as the work feed, and
so it first hits the uncut surface and immediately plunges in
and starts cutting. If a chip is still attached to the cutting
edge, the abrupt impact with the workpiece just knocks it off.

The downside to climb milling is it can pull the work and table
into the cutter by the amount of backlash in the machine. If
you have a lot of backlash (0.010" is enough to make real
problems) you can only climb mill on light cuts, or you have to
apply a lot of drag with the axis clamps. If you always make a
light finish cut (like .005") in the climb-mill direction, you
will get rid of the rough surface.

If your machine is tight, then you can climb-mill all the time,
and extend your tool life. That skating at the beginning wears
out cutting tools very early.

Jon

"Tom Gardner" wrote in message
. net...
snip---

I NEVER though I'd be asking a speed/feed/lube question but I'm curious
as to how I can do this better. Is the 6061 just softer/gummier? I have
54 more parts to make and as much as I like doing the work I hate wasting
time scraping the parts. I hate cleaning lube off of them too. Actually,
I think I'd much rather just draw the stuff and have it magically appear
on my desk.


What Ned said, and don't be afraid to moisten the cut with some kerosene.
What's happening is you're getting a slight amount of chip welding to the
cutter, which then streaks off on the part. A tiny amount of lubrication
will prevent that from happening, and improve the surface finish in ways you
won't believe. Something as simple as dragging a moistened acid brush on the
cutter will make a huge difference. You need not flood the material, and if
you have an aversion to kerosene, use some paint thinner. If you choose
paint thinner, it will even evaporate cleanly, so it's not very messy. Don't
machine aluminum dry if you want good performance. Use an air hose for
cleanup. Those of us that work(ed) in the industry do-----and none of us
are dead up to this point. Air hoses are an important part of a shop. .
Just don't blow chips towards the ways.

The nice material you spoke of is likely 7075------if not, it's likely 2024.
Both of them machine much nicer than 6061, which tends to be a little soft
by comparison, assuming they are artificially aged (T condition from T351
upwards). 7075 is high in zinc, and cuts very clean, with a shiny surface.
2024 cuts fairly cleanly, but never with a shiny surface.

Did you use the same end mill for machining steel previously? That's a
mistake. End mills that are ground for steel have less clearance, and lose
the keen edge, desirable for aluminum, fairly quickly---------resulting in a
poor finish when used on aluminum.

There are special grinds available expressly for aluminum----might be worth
the investment. They're marked aluminum on the shank.

Harold

By the way, less smelly kerosene is being sold for decorative lamps.

i

Tom Gardner wrote:
I get to make a boatload of small accurate parts from 6061 Al, mostly 1/2"
stock. I sooo like Aluminum! I bought a bunch of different size stock bars
from McMaster, they deliver the SAME day, how cool is that! But, squaring
up my sawed pieces with very light cuts in the BP has me a bit confused as
to how I'm getting tiny amounts of swarf that are 'kinda welded on the cut
surface. It seems to scrape off easily. I'm using the side of a new 3/4"
HSS end mill without lube and clamping the pieces in the vise and cranking
the "Y" handle.

Years ago I bought a large amount of Al drops that were some kind of
high-strength aircraft alloy, I don't know what it is but it machines
beautifully and no swarfy-sticky issue. I NEVER though I'd be asking a
speed/feed/lube question but I'm curious as to how I can do this better. Is
the 6061 just softer/gummier? I have 54 more parts to make and as much as I
like doing the work I hate wasting time scraping the parts. I hate cleaning
lube off of them too. Actually, I think I'd much rather just draw the stuff
and have it magically appear on my desk.



I use mineral spirits for cutting, and especially tapping, the gummy
aluminums. It evaporates off the parts fairly quickly. Yes, it is
somewhat flammable, I apply with an acid brush sparingly. Get the
'odorless' variety, while not totally odorless it's not too bad. I've
also applied it out of something like an Elmer's Glue bottle, just
letting it drip from the spout, not squirting it. If you have work
lights close at hand keep it out of them just to be safe.

Regards
Paul


--
-----------------------------------------
It's a Linux world....well, it oughta be.
-----------------------------------------

Jon Elson wrote:
... "climb milling", ...
The downside to climb milling is it can pull the work and table into the
cutter by the amount of backlash in the machine. ...

Disclaimer: I am a total greenhorn at milling, so take what I say with a
grain of salt, as they say. Also, I have a small horizontal mill, if
that makes a difference.

When I climb mill I take small cuts (.005 or less) AND I use hand
pressure on the table to take out the backlash. I.e., I push on the
table in the direction of travel. Works for me.

Bob

Bob Engelhardt wrote:


When I climb mill I take small cuts (.005 or less) AND I use hand
pressure on the table to take out the backlash. I.e., I push on the
table in the direction of travel. Works for me.

Bob



Does your mill have table locks? Just snug them up a little bit for some
resistance.

Oh...........


"in the direction of travel" ?? So the screw isn't advancing the table,
only keeping it from advancing?

Randy

Ignoramus2733 wrote:
By the way, less smelly kerosene is being sold for decorative lamps.

i

"Ultra-Pure Lamp and Candle Oil" ???
I use it for valve oil on my trumpet. I haven't tried it for cutting
fluid (I wonder why not). I got onto an argument with a guy on a trumpet
forum as to whether it is kerosene or not. He said yes, I said no.
Apparently it is a highly refined kerosene (shrug).
Randy

On Sat, 25 Aug 2007 02:50:52 GMT, "Tom Gardner"
wrote:

I get to make a boatload of small accurate parts from 6061 Al, mostly 1/2"
stock. I sooo like Aluminum! I bought a bunch of different size stock bars
from McMaster, they deliver the SAME day, how cool is that! But, squaring
up my sawed pieces with very light cuts in the BP has me a bit confused as
to how I'm getting tiny amounts of swarf that are 'kinda welded on the cut
surface. It seems to scrape off easily. I'm using the side of a new 3/4"
HSS end mill without lube and clamping the pieces in the vise and cranking
the "Y" handle.

Years ago I bought a large amount of Al drops that were some kind of
high-strength aircraft alloy, I don't know what it is but it machines
beautifully and no swarfy-sticky issue. I NEVER though I'd be asking a
speed/feed/lube question but I'm curious as to how I can do this better. Is
the 6061 just softer/gummier? I have 54 more parts to make and as much as I
like doing the work I hate wasting time scraping the parts. I hate cleaning
lube off of them too. Actually, I think I'd much rather just draw the stuff
and have it magically appear on my desk.

==========
Two items:

(1) In addition to the alloy specification there is a heat treat
condition designated by T as 6061-T6. This is a hardened
condition and machines much nicer. More than likely this was
your aircraft alloy.

(2) Try using WD-40 spray for the lube, if this is actually a
lube problem. If you need a larger coolant flow to mechanically
remove the chips because they are getting re-cut and welded to
the part a "mist lubricator" works wells [if you have compressed
air] but is messy. The air flow blows the chips out of the cut
zone in addition to the cool lubricant. Indeed you may try just
an air blast first.
see
http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMK3
http://www.use-enco.com/CGI/INLMK3?PMK0NO=841066

Should be available at most any good mill supply.

Unka' George [George McDuffee]
============
Merchants have no country.
The mere spot they stand on
does not constitute so strong an attachment
as that from which they draw their gains.

Thomas Jefferson (1743-1826),
U.S. president. Letter, 17 March 1814.

On Aug 24, 10:49 pm, "Harold and Susan Vordos" wrote:

The nice material you spoke of is likely 7075------if not, it's likely 2024.
Both of them machine much nicer than 6061, which tends to be a little soft
by comparison, assuming they are artificially aged (T condition from T351
upwards). 7075 is high in zinc, and cuts very clean, with a shiny surface.
2024 cuts fairly cleanly, but never with a shiny surface.

There's a freecutting aluminum: 2011T3. Not really common, but
I used a lot of it years ago to make intricate fittings for air brake
valves. It cuts really nicely, with the short chips familiar to some
in the leaded steels like 12L14. And it has the same cold-shortness as
the freecutting steels. Cracks easily when bent. And corrodes quickly,
too, due to the copper content. Can't have everything.

Dan

Randy Replogle wrote:
Does your mill have table locks? ...

Not on the X axis. I've always thought that it should.

"in the direction of travel" ?? So the screw isn't advancing the table,
only keeping it from advancing?

Now that you put it that way, you're right. The feed nut is bearing on
the back of the screw thread and turning the screw just lets the table
advance from my pushing on it.

Bob

Tom Gardner wrote:

I get to make a boatload of small accurate parts from 6061 Al, mostly 1/2"
stock. I sooo like Aluminum! I bought a bunch of different size stock bars
from McMaster, they deliver the SAME day, how cool is that! But, squaring
up my sawed pieces with very light cuts in the BP has me a bit confused as
to how I'm getting tiny amounts of swarf that are 'kinda welded on the cut
surface. It seems to scrape off easily. I'm using the side of a new 3/4"
HSS end mill without lube and clamping the pieces in the vise and cranking
the "Y" handle.

Years ago I bought a large amount of Al drops that were some kind of
high-strength aircraft alloy, I don't know what it is but it machines
beautifully and no swarfy-sticky issue. I NEVER though I'd be asking a
speed/feed/lube question but I'm curious as to how I can do this better. Is
the 6061 just softer/gummier? I have 54 more parts to make and as much as I
like doing the work I hate wasting time scraping the parts. I hate cleaning
lube off of them too. Actually, I think I'd much rather just draw the stuff
and have it magically appear on my desk.




As much maligned as water soluble lube is (AKA toilet water) it works
well for this. Even a little brushed on will help stop chip weld to the
cutter.

It washes off with hot water! :-)

When I have to clean up ends like that, I do it in two passes.
Conventional to remove the bulk, and climb back.(or was it the other way
round?) Power feed is pretty much a requirement, to make it work without
being work, though. I suppose lever feed on a small mill would do the
same. The first crossing of the cutter has a bit of spring to it,
allowing for there to be a bit of material removed on the second pass.

Puts the vise back at the same start point, too.

Whatever you do, try to keep the stock from heating up. Hot aluminum
becomes soft aluminum. Sorta like machining warm chewing gum. Ewww!
6061 round is usually -T6 IIRC. Should machine OK, but not as well as
7075, or 2024 of similar hardness.

Cheers
Trevor Jones

In article i6Zzi.2449$Pd4.2008@edtnps82, Trevor Jones wrote:

Whatever you do, try to keep the stock from heating up. Hot aluminum
becomes soft aluminum. Sorta like machining warm chewing gum. Ewww!

How hot is too hot? Not looking for a specific temperature here, but general
guidelines -- obviously a dull red glow would fit in the "too hot" category,
but where does "too hot" begin on a scale like warm to the touch,
uncomfortably warm, painfully hot to the touch, sizzles when water dripped on
it, etc?

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

Doug Miller wrote:
In article i6Zzi.2449$Pd4.2008@edtnps82, Trevor Jones wrote:


Whatever you do, try to keep the stock from heating up. Hot aluminum
becomes soft aluminum. Sorta like machining warm chewing gum. Ewww!


How hot is too hot? Not looking for a specific temperature here, but general
guidelines -- obviously a dull red glow would fit in the "too hot" category,
but where does "too hot" begin on a scale like warm to the touch,
uncomfortably warm, painfully hot to the touch, sizzles when water dripped on
it, etc?

Chips go dead soft, part builds up heat. Uncomfortable warm. That kind
of range.

You know you are too hot when the chips start to bung up the flutes, eh!
Watching the behavior of the material while it is being cut is a
pretty good indicator. If it starts to smear, it's definately too hot,
the tool is too dull, or both.

For the most part, too hot to touch the part, right after a cut, is
way too hot, IMO. It's a good place to start, for me, anyways.

I think you would have a puddle, if you got a dull red.:-)

I like coolant, if I can use it. The mess is often worth it, for the
easier machining, and finish.

For annealing aluminum, I have used a sharpie marker, and heated until
the line dissapeared. That leaves the area dead soft. It will naturally
age harden to about a -T3 temper in a few weeks. In a general sense, anyway.

The specific heat treat schedules for specific alloys have to be
followed if you want exact type results.


Cheers
Trevor Jones

In article J30Ai.9739$vP5.6944@edtnps90, Trevor Jones wrote:
Doug Miller wrote:
In article i6Zzi.2449$Pd4.2008@edtnps82, Trevor Jones
wrote:


Whatever you do, try to keep the stock from heating up. Hot aluminum
becomes soft aluminum. Sorta like machining warm chewing gum. Ewww!


How hot is too hot? Not looking for a specific temperature here, but general
guidelines -- obviously a dull red glow would fit in the "too hot" category,
but where does "too hot" begin on a scale like warm to the touch,
uncomfortably warm, painfully hot to the touch, sizzles when water dripped on

it, etc?

Chips go dead soft, part builds up heat. Uncomfortable warm. That kind
of range.

You know you are too hot when the chips start to bung up the flutes, eh!
Watching the behavior of the material while it is being cut is a
pretty good indicator. If it starts to smear, it's definately too hot,
the tool is too dull, or both.

For the most part, too hot to touch the part, right after a cut, is
way too hot, IMO. It's a good place to start, for me, anyways.

Thanks!

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

Doug Miller wrote:

In article i6Zzi.2449$Pd4.2008@edtnps82, Trevor Jones wrote:

Whatever you do, try to keep the stock from heating up. Hot aluminum
becomes soft aluminum. Sorta like machining warm chewing gum. Ewww!

How hot is too hot? Not looking for a specific temperature here, but general
guidelines -- obviously a dull red glow would fit in the "too hot" category,
but where does "too hot" begin on a scale like warm to the touch,
uncomfortably warm, painfully hot to the touch, sizzles when water dripped on
it, etc?

As anyone who's welded aluminum knows, it doesn't glow, it just gets
liquid. You aren't going to get smoking blue chips flying like you do
with steel to clue you in as to the temp of the AL you're milling.
Uncomfortably warm is nothing on a metallurgical level. If it's hot
enough to sizzle water it may still not be truly too hot
metallurgically, but it could also be. I'd say painfully hot to touch is
when you should look for coolant options.

"Tom Gardner" wrote in
. net:


Years ago I bought a large amount of Al drops that were some kind of
high-strength aircraft alloy, I don't know what it is but it machines
beautifully and no swarfy-sticky issue. I NEVER though I'd be asking
a speed/feed/lube question but I'm curious as to how I can do this
better. Is the 6061 just softer/gummier? I have 54 more parts to
make and as much as I like doing the work I hate wasting time scraping
the parts. I hate cleaning lube off of them too. Actually, I think
I'd much rather just draw the stuff and have it magically appear on my
desk.



Heh..I'll spare you the description on how to _really_ machine aluminum,
but for your application and situation, I would suggest some 3-36 and
climb milling, at least on the last cut. An air nozzle aimed at the cut
can help too. Don't spare the feed or rpm either.


--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

"Trevor Jones" wrote in message
news:J30Ai.9739$vP5.6944@edtnps90...
snip------

For the most part, too hot to touch the part, right after a cut, is way
too hot, IMO. It's a good place to start, for me, anyways.

While it's not comfortable to hold, such a part will not have its hardness
effected. The soak temperature for artificial aging is much higher.

For annealing aluminum, I have used a sharpie marker, and heated until
the line dissapeared. That leaves the area dead soft. It will naturally
age harden to about a -T3 temper in a few weeks. In a general sense,
anyway.

Only if it is taken to a full solution anneal first. That requires a
temperature of about 950 degrees F for a period of time. Once a piece has
been heated to the point of losing its T condition, it will not return
without the solution anneal, even by furnace.

The specific heat treat schedules for specific alloys have to be followed
if you want exact type results.

Precisely!!

Harold