End Milling Into a Corner Without 'Snipe'?
 

I have a technique question about milling. Lets say I'm machining a
rectangular pocket, or just an inside corner of an "L" in something. I'm
coming along one wall, using conventional milling. When I get to the
corner and touch the next wall, the end mill will want to flex sideways
and dig in a little bit into the wall I just finished. This produces a
small 'snipe' (a woodworking term, not sure if there is a metalworking
specific equivalent) which looks a little fugly. I'm not sure if using
climb milling will help or hurt. I think you just end up with a snipe
in the next wall instead of the one you just finished. I have a small
Clausing mill, which isn't the most rigid thing on the planet, and
probably makes matters worse. I need to do something in stainless, and
cosmetics are important. The stainless makes taking light cuts
difficult, and the cosmetic issue means I really don't want a divot in
the corner.

Any suggestions or tricks?

Thanks!

Doug White

End Milling Into a Corner Without 'Snipe'?
 

Doug,
For finish cuts, I prefer HSS.

I like to climb on finsh cuts, .005" DOC, .0005" per tooth.

Stainless can be a real bitch. Some can work harden to the point that
you think you have hit carbide. NEVER let a tool rub on Stainless,
(HSS or carbide tooling). Cut or get off the part. Same is true of
drilling.
Dave





On Feb 17, 7:25 pm, (Doug White) wrote:
I have a technique question about milling. Lets say I'm machining a
rectangular pocket, or just an inside corner of an "L" in something. I'm
coming along one wall, using conventional milling. When I get to the
corner and touch the next wall, the end mill will want to flex sideways
and dig in a little bit into the wall I just finished. This produces a
small 'snipe' (a woodworking term, not sure if there is a metalworking
specific equivalent) which looks a little fugly. I'm not sure if using
climb milling will help or hurt. I think you just end up with a snipe
in the next wall instead of the one you just finished. I have a small
Clausing mill, which isn't the most rigid thing on the planet, and
probably makes matters worse. I need to do something in stainless, and
cosmetics are important. The stainless makes taking light cuts
difficult, and the cosmetic issue means I really don't want a divot in
the corner.

Any suggestions or tricks?

Thanks!

Doug White

End Milling Into a Corner Without 'Snipe'?
 

What's that Lassie? You say that Doug White fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Mon, 18 Feb 2008 03:25:57 GMT:

I have a technique question about milling. Lets say I'm machining a
rectangular pocket, or just an inside corner of an "L" in something. I'm
coming along one wall, using conventional milling. When I get to the
corner and touch the next wall, the end mill will want to flex sideways
and dig in a little bit into the wall I just finished. This produces a
small 'snipe' (a woodworking term, not sure if there is a metalworking
specific equivalent) which looks a little fugly.


If you take a light cut this won't happen as much.
Rough out the shape(leaving a 'snipe'), then go back and finish cut
(to remove the 'snipe' from the first pass).

Dan
--

Dan

End Milling Into a Corner Without 'Snipe'?
 

"Doug White" wrote in message
...
I have a technique question about milling. Lets say I'm machining a
rectangular pocket, or just an inside corner of an "L" in something. I'm
coming along one wall, using conventional milling. When I get to the
corner and touch the next wall, the end mill will want to flex sideways
and dig in a little bit into the wall I just finished. This produces a
small 'snipe' (a woodworking term, not sure if there is a metalworking
specific equivalent) which looks a little fugly. I'm not sure if using
climb milling will help or hurt. I think you just end up with a snipe
in the next wall instead of the one you just finished. I have a small
Clausing mill, which isn't the most rigid thing on the planet, and
probably makes matters worse. I need to do something in stainless, and
cosmetics are important. The stainless makes taking light cuts
difficult, and the cosmetic issue means I really don't want a divot in
the corner.

Any suggestions or tricks?

Thanks!

Doug White

You can minimize the problem by "sneaking up" on the final dimensions. Cut
a little under (maybe 0.010 or so) and then take a final cut to take that
last ten thou... Or, as an old machine shop instructor put it, "On the last
cut, make Brillo..."

Jerry

End Milling Into a Corner Without 'Snipe'?
 

On Mon, 18 Feb 2008 03:25:57 GMT, (Doug White) wrote:



Any suggestions or tricks?

Thanks!

Doug White


Use a slot drill (two flute centre cutting cutter) if you really must avoid
the digging in. It will protect you because the front flute will be clear of
the cut before the back flute is close enough to risk digging in.


Mark Rand
RTFM

End Milling Into a Corner Without 'Snipe'?
 

Keywords:
In article , Mark Rand wrote:
On Mon, 18 Feb 2008 03:25:57 GMT, (Doug White) wrote:



Any suggestions or tricks?

Thanks!

Doug White


Use a slot drill (two flute centre cutting cutter) if you really must avoid
the digging in. It will protect you because the front flute will be clear of
the cut before the back flute is close enough to risk digging in.

That's a good idea. I don't have many two flute end mills, but it's
something I should invest in.

One question: If the idea is to make sure it's only making contact on
one edge at a time, should I use a straight flute end mill? I don't have
to worry about lifting chips out of a pocket for my immediate problem,
and it seems to me that a spiral flute end mill would defeat the
advantage of two flutes for this operation.

Thanks!

Doug White

End Milling Into a Corner Without 'Snipe'?
 

On Feb 17, 10:25*pm, (Doug White) wrote:
The stainless makes taking light cuts
difficult, and the cosmetic issue means I really don't want a divot in
the corner.

Any suggestions or tricks?

Easy.

Before you begin cutting the pocket, move to each corner location of
your pocket (final dimensions!). Drill just under the endmill's
diameter (between like 1/64" and 1/16", depending on the size of the
endmill), and then plunge down with the endmill. Now you've created
your finished corners.

When you're machining your pocket, your cutter will actually come
completely out the cut as you reach the corners, instead of having a
*massive* chip load increase (as you're experiencing now) which flexes
the cutter.

You can't simply rely in "slowing down" at the corners. We're not CNC
machines - we're flimbsy, fleshy, squishy humans, and the machines
have backlash.

Climb milling is a good idea for your finishing cuts. When on a CNC,
you normally climb mill because it results in a better finish and
longer cutter life. Just make sure the machine is tight and you're
paying attention (listening, feeling and looking).

Additionally, climb milling should help with the issues associated
with taking light cuts in stainless. When you climb mill, the chip
load is at its max as the flute enters the work (good). When
conventional milling, the chip load is at its smallest as the flute
enters the cut (bad). This alone will let you take light cuts in
stainless successfully.

Lastly, make sure you know which way to turn the handwheel as you
switch your axis feed! This is no time to be second guessing! Draw
arrows on the machine just above the handwheels. *Always* think in
terms of where the cutter is going to go - not which direction the
axis will be moving (i.e. turn the handwheel clockwise to move the
CUTTER towards me). Different machines move in different ways so
always think in terms of cutter direction.

Regards,

Robin