I need to mill a pocket 1 x 2, 5/16 deep in
a rectangular block of aluminum.

Normally I'd try to get a slot going with an end mill.
That's not easy as your cutting 3 sides at the same time.
So I end up taking fairly small cuts back and forth
until I get the slot open enough to take deeper cuts
with the side of the end mill.

Once the center is out the rest of the job is easy, just
finish up with a end mill.

So what's the better way to hog out most of the center?
Swiss cheese it with a drill bit 1st?

Thanks,
Wayne D.

Wayne wrote:
I need to mill a pocket 1 x 2, 5/16 deep in
a rectangular block of aluminum.

Normally I'd try to get a slot going with an end mill.
That's not easy as your cutting 3 sides at the same time.
So I end up taking fairly small cuts back and forth
until I get the slot open enough to take deeper cuts
with the side of the end mill.

Once the center is out the rest of the job is easy, just
finish up with a end mill.

So what's the better way to hog out most of the center?
Swiss cheese it with a drill bit 1st?

Get some roughing cutters. They
won't load up nearly as bad as
finish cutters. Use air to blow
out the chips as you go.

Wayne wrote:


So what's the better way to hog out most of the center?
Swiss cheese it with a drill bit 1st?

You can do that with the endmill ( a center-cutting one). That's why
they're sharp on the ends.
draw the perimeter of the pocket with a Sharpie or a scriber, set the
depth stop to something shallower than the finish depth and go to it.
Randy

Wayne wrote:

I need to mill a pocket 1 x 2, 5/16 deep in
a rectangular block of aluminum.

Normally I'd try to get a slot going with an end mill.
That's not easy as your cutting 3 sides at the same time.
So I end up taking fairly small cuts back and forth
until I get the slot open enough to take deeper cuts
with the side of the end mill.

Once the center is out the rest of the job is easy, just
finish up with a end mill.

So what's the better way to hog out most of the center?
Swiss cheese it with a drill bit 1st?

Thanks,
Wayne D.

Perhaps drilling a hole a bit larger than your end mill dia first and
then starting the end mill in that hole so you're just side cutting as
you go around removing material. Wouldn't want to swiss cheese it as
that would give a lot of interrupted cuts and shock loading on your end
mill.

"Wayne" wrote in message
news
I need to mill a pocket 1 x 2, 5/16 deep in
a rectangular block of aluminum.

Normally I'd try to get a slot going with an end mill.
That's not easy as your cutting 3 sides at the same time.
So I end up taking fairly small cuts back and forth
until I get the slot open enough to take deeper cuts
with the side of the end mill.

Once the center is out the rest of the job is easy, just
finish up with a end mill.

So what's the better way to hog out most of the center?
Swiss cheese it with a drill bit 1st?

Thanks,
Wayne D.

They make a high helix 2 or 3 flute center cut endmill just
for non-ferrous.
Buy one, use it for aluminum ONLY.

I crank up the speed, squirt on a little aluminum cutting
juice, and make (lots of)
chips.

Wayne wrote:

I need to mill a pocket 1 x 2, 5/16 deep in
a rectangular block of aluminum.

And what radius in the corners?

Normally I'd try to get a slot going with an end mill.

Normally, I use an endmill with the diameter of the corners (of the pocket;
assuming the radius is not too small). Then I simply mill a rectangle about
1mm off the finished pocket and a bit less deeper then required. Crank out
any remaining material, feed downwards to the finished depth, mill along
the pocket's boundary and mill off any island remaining inside.

That's not easy as your cutting 3 sides at the same time.

That doesn't matter and I don't understand what's complicated there.


Nick
--
The lowcost-DRO:
http://www.yadro.de

Wayne wrote in
news
I need to mill a pocket 1 x 2, 5/16 deep in
a rectangular block of aluminum.

Normally I'd try to get a slot going with an end mill.
That's not easy as your cutting 3 sides at the same time.
So I end up taking fairly small cuts back and forth
until I get the slot open enough to take deeper cuts
with the side of the end mill.

Once the center is out the rest of the job is easy, just
finish up with a end mill.

So what's the better way to hog out most of the center?
Swiss cheese it with a drill bit 1st?

Thanks,
Wayne D.


Wayne,
Make sure the EM you are using is center cutting. You can tell by looking
at the end, depending on the number of flutes, at least 1 will be
sharpened across the center of the end mill. A non-center cutting EM will
not have a flute across the centerline.
You should be able to plunge straight in with the EM if it's center
cutting. As someone else noted, use a 3 flute, and keep the chips out of
the cut.

--
Anthony

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

Remove sp to reply via email

On Nov 27, 4:07 pm, Wayne wrote:
not easy as your cutting 3 sides at the same time.
So I end up taking fairly small cuts back and forth
until I get the I need to mill a pocket 1 x 2, 5/16 deep in
a rectangular block of aluminum.


So what's the better way to hog out most of the center?
Swiss cheese it with a drill bit 1st?

Thanks,
Wayne D.

Can't imagine why you'd consider drilling. A center cutting endmill
cuts very well on its end.

John Martin

Wayne wrote:
I need to mill a pocket 1 x 2, 5/16 deep in
a rectangular block of aluminum.
Normally I'd try to get a slot going with an end mill.
That's not easy as your cutting 3 sides at the same time.
So I end up taking fairly small cuts back and forth
until I get the slot open enough to take deeper cuts
with the side of the end mill.
Once the center is out the rest of the job is easy, just
finish up with a end mill.
So what's the better way to hog out most of the center?
Swiss cheese it with a drill bit 1st?

Get some roughing cutters. They
won't load up nearly as bad as
finish cutters. Use air to blow
out the chips as you go.



I forgot I bought a roughing cutter years back when I
thought I'd be doing a rather large pocket. I gave
it a try and it worked quite well.

Wayne D.

On Tue, 27 Nov 2007 16:02:01 -0600, Nick Mueller
wrote:

Wayne wrote:

I need to mill a pocket 1 x 2, 5/16 deep in
a rectangular block of aluminum.

And what radius in the corners?

For this job the radius isn't important. On other jobs as small
as possible.


Normally I'd try to get a slot going with an end mill.

Normally, I use an endmill with the diameter of the corners (of the
pocket;
assuming the radius is not too small). Then I simply mill a rectangle
about
1mm off the finished pocket and a bit less deeper then required. Crank
out
any remaining material, feed downwards to the finished depth, mill along
the pocket's boundary and mill off any island remaining inside.

That's not easy as your cutting 3 sides at the same time.

That doesn't matter and I don't understand what's complicated there.


When I did this before with a 3/16 end mill I got a lot of chatter.


Nick



--
Wayne D.

On Tue, 27 Nov 2007 17:24:13 -0600, Anthony wrote:

Wayne wrote in
news
I need to mill a pocket 1 x 2, 5/16 deep in
a rectangular block of aluminum.

Normally I'd try to get a slot going with an end mill.
That's not easy as your cutting 3 sides at the same time.
So I end up taking fairly small cuts back and forth
until I get the slot open enough to take deeper cuts
with the side of the end mill.

Once the center is out the rest of the job is easy, just
finish up with a end mill.

So what's the better way to hog out most of the center?
Swiss cheese it with a drill bit 1st?

Thanks,
Wayne D.


Wayne,
Make sure the EM you are using is center cutting. You can tell by looking
at the end, depending on the number of flutes, at least 1 will be
sharpened across the center of the end mill. A non-center cutting EM will
not have a flute across the centerline.
You should be able to plunge straight in with the EM if it's center
cutting. As someone else noted, use a 3 flute, and keep the chips out of
the cut.


So that's how you tell if they center cutting.

Wayne D.

That's not easy as your cutting 3 sides at the same time.

That doesn't matter and I don't understand what's complicated there.


When I did this before with a 3/16 end mill I got a lot of chatter.

James Harvey (Machine Shop Trade Secrets) cautions against it; he
apparently had an endmill try to climb a pocket wall or something like
that. FWIW, I do not see any way to follow his resulting advice (which
AFAICT is "don't do it"), so I simply proceed with caution.

I find that the up-milling side of any slot takes a little bit of a
beating, at least with my machine. I compensate by leaving a little
extra material for cleanup.

Bill

Wayne wrote in
news
So that's how you tell if they center cutting.

Wayne D.

Wayne,
Wasn't trying for the smart-ass of the month award. I used to teach
machining at the local adult vo-tech and you would be suprised at the
number of people who had been cutting metal for many years who didn't know
the difference between the two types.
I plunge mill aluminum extrusions on almost a daily basis, either for
anchor fasteners or cbores for bolt heads, etc. You do have to watch your
feed though, too much and the em will start walking, as there isn't much
flute available at the center to let the chips out.

--
Anthony

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

Remove sp to reply via email

Wayne wrote:

When I did this before with a 3/16 end mill I got a lot of chatter.

Feed rate, rpm, depth of cut, spindle, lubrication. Can all be fixed and
chatter doesn't matter that much when you are roughening. Simply don't try
to mill to size with the very first pass.
So your end mill always has to be smaller than the smallest dimension of the
pocket.
Except you have a rigid mill.


Nick
--
The lowcost-DRO:
http://www.yadro.de

So that's how you tell if they center cutting.

Wayne D.

Wayne,
Wasn't trying for the smart-ass of the month award. I used to teach
machining at the local adult vo-tech and you would be suprised at the
number of people who had been cutting metal for many years who didn't
know
the difference between the two types.
I plunge mill aluminum extrusions on almost a daily basis, either for
anchor fasteners or cbores for bolt heads, etc. You do have to watch your
feed though, too much and the em will start walking, as there isn't much
flute available at the center to let the chips out.


Anthony,
I took it as you intended.
The only way I previously knew my end mills were center cutting
was that was what I bought. So I learned something.

Wayne D.

On 2007-11-29, Wayne wrote:

[ ... ]

Wasn't trying for the smart-ass of the month award. I used to teach
machining at the local adult vo-tech and you would be suprised at the
number of people who had been cutting metal for many years who didn't
know
the difference between the two types.
I plunge mill aluminum extrusions on almost a daily basis, either for
anchor fasteners or cbores for bolt heads, etc. You do have to watch your
feed though, too much and the em will start walking, as there isn't much
flute available at the center to let the chips out.


Anthony,
I took it as you intended.
The only way I previously knew my end mills were center cutting
was that was what I bought. So I learned something.

Note, BTW, that while center-cutting end mills will plunge, they
are not very good at it -- just much better than non center-cutting end
mills.

So -- if you have room, the best way down is to ramp down --
feed sideways somewhat faster than you plunge. This clears the chips
better. And it is the way that CNC machines normally cut pockets.

Enjoy,
DoN.

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