Hello all,

I will need to mill a roughly 4x4 inch rectangular hole in what amounts
to a thin plate (it's actually a truly ugly pot metal - you have to cut
it to understand). In the past, I have rough cut these holes with a
buzz saw. Armed with my mill/drill, my options appear to be: rough cut,
only smaller and mill a clean edge; plunge and turn the entire hole into
chips; or (this is the one that has me wondering about safety) mill a
rectangular edge and let the resulting plate fall away. Is the latter
an option? Perhaps the best idea is to drill and clamp the piece to be
released, and then just mill the boundary with both pieces clamped in
place??

I have read a lot about table saw safety (which I am convinced has
spared me a board in the gut on more than one occaision), and am
wondering whether there are similar dangers to be avoided on a mill.
Normally, the metal I remove is reduced to chips. Are there other safe
options?

Thanks!

Bill

On Sat, 22 Oct 2005 17:11:39 GMT, Bill Schwab
wrote:

Hello all,

I will need to mill a roughly 4x4 inch rectangular hole in what amounts
to a thin plate (it's actually a truly ugly pot metal - you have to cut
it to understand). In the past, I have rough cut these holes with a
buzz saw. Armed with my mill/drill, my options appear to be: rough cut,
only smaller and mill a clean edge; plunge and turn the entire hole into
chips; or (this is the one that has me wondering about safety) mill a
rectangular edge and let the resulting plate fall away.



I do it all the time. The inside piece can come up and go flying. Make
sure there aren't any chips underneath to keep it from dropping and
feed slowly when the part is about to break loose.
Randy



Is the latter
an option? Perhaps the best idea is to drill and clamp the piece to be
released, and then just mill the boundary with both pieces clamped in
place??

I have read a lot about table saw safety (which I am convinced has
spared me a board in the gut on more than one occaision), and am
wondering whether there are similar dangers to be avoided on a mill.
Normally, the metal I remove is reduced to chips. Are there other safe
options?

Thanks!

Bill

another alternative is to use a large diameter hole saw to remove
the bulk of the mateiral. Costs are generally about 10$ for the
adapter/hoilder and 10$ for a given size saw. 2 good US brands
ar Morse and Starrett. One trick is to drill a smaller hole in a
corner that the saw blade will cross to allow the swarf to exit
easily. I have used this up to 1 inch thick steel. Deeper saws
are available and you can drill the pilot hole through so you can
saw from both sides.

GmcD

On Sat, 22 Oct 2005 17:30:59 GMT, Randy Replogle
wrote:

On Sat, 22 Oct 2005 17:11:39 GMT, Bill Schwab
wrote:

Hello all,

I will need to mill a roughly 4x4 inch rectangular hole in what amounts
to a thin plate (it's actually a truly ugly pot metal - you have to cut
it to understand). In the past, I have rough cut these holes with a
buzz saw. Armed with my mill/drill, my options appear to be: rough cut,
only smaller and mill a clean edge; plunge and turn the entire hole into
chips; or (this is the one that has me wondering about safety) mill a
rectangular edge and let the resulting plate fall away.



I do it all the time. The inside piece can come up and go flying. Make
sure there aren't any chips underneath to keep it from dropping and
feed slowly when the part is about to break loose.
Randy



Is the latter
an option? Perhaps the best idea is to drill and clamp the piece to be
released, and then just mill the boundary with both pieces clamped in
place??

I have read a lot about table saw safety (which I am convinced has
spared me a board in the gut on more than one occaision), and am
wondering whether there are similar dangers to be avoided on a mill.
Normally, the metal I remove is reduced to chips. Are there other safe
options?

Thanks!

Bill

"Randy Replogle" wrote in message
...
On Sat, 22 Oct 2005 17:11:39 GMT, Bill Schwab
wrote:

Hello all,

I will need to mill a roughly 4x4 inch rectangular hole in what amounts
to a thin plate (it's actually a truly ugly pot metal - you have to cut
it to understand). In the past, I have rough cut these holes with a
buzz saw. Armed with my mill/drill, my options appear to be: rough cut,
only smaller and mill a clean edge; plunge and turn the entire hole into
chips; or (this is the one that has me wondering about safety) mill a
rectangular edge and let the resulting plate fall away.



I do it all the time. The inside piece can come up and go flying. Make
sure there aren't any chips underneath to keep it from dropping and
feed slowly when the part is about to break loose.
Randy



I've done this many times, too. I've never had the mill toss things very
far (more than a few inches). One thing to remember, a large cutter turning
slowly will be more inclined to throw things than a small cutter turning
fast. And roughing mills are more inclined to throw things than a finish
mill. A friend of mine (a master tool and die maker) keeps handy a piece of
plywood with a handle on it that he holds up like a shield to deflect flying
"stuff" (mostly because he doesn't like getting hit with hot chips...).

The big hazard with cutting a chunk out of the middle of a piece is that, if
the chunk is too big with respect to the remaining metal, the work can bow
and come out of the vise. This is usually MUCH more exciting than what
happens to the piece you cut out...

The basic rule in using any machine (any tool, for that matter) is to think
about what you are doing and, if you know an operation is hazardous, or just
aren't too sure, take the necessary precautions to protect yourself, the
machine and the work IN THAT ORDER. Far too many injuries (and busted
machines) result when something happens and someone makes a grab for
something trying to salvage the work.

Jerry

I'd mount the piece to the mill table with the bolt(s) going through the
part to be removed. Put a piece of 1/8" plywood underneath when you do this
so you don't cut the table of the mill. Plunge in one corner and go around
the edge of what you want and one pass will do the whole thing. The big
piece will pop up when you have the cut done and really won't go anywhere.

--
Why do penguins walk so far to get to their nesting grounds?

Jerry,

I've done this many times, too. I've never had the mill toss things very
far (more than a few inches). One thing to remember, a large cutter turning
slowly will be more inclined to throw things than a small cutter turning
fast. And roughing mills are more inclined to throw things than a finish
mill. A friend of mine (a master tool and die maker) keeps handy a piece of
plywood with a handle on it that he holds up like a shield to deflect flying
"stuff" (mostly because he doesn't like getting hit with hot chips...).

Funny, I did something similar just today: used cardboard to deflect
wood chips from the cross-travel ways.


The big hazard with cutting a chunk out of the middle of a piece is that, if
the chunk is too big with respect to the remaining metal, the work can bow
and come out of the vise. This is usually MUCH more exciting than what
happens to the piece you cut out...

Back to the serious, I will keep that in mind. In this case, the
work will be too large for the vice, unless I attach something to it and
in turn put that in the vice. By the time I get that right, it will be
easier to remove the vice and use clamps.


The basic rule in using any machine (any tool, for that matter) is to think
about what you are doing and, if you know an operation is hazardous, or just
aren't too sure, take the necessary precautions to protect yourself, the
machine and the work IN THAT ORDER.

Good advice - thanks!

Bill

Bob,

I'd mount the piece to the mill table with the bolt(s) going through the
part to be removed. Put a piece of 1/8" plywood underneath when you do this
so you don't cut the table of the mill. Plunge in one corner and go around
the edge of what you want and one pass will do the whole thing. The big
piece will pop up when you have the cut done and really won't go anywhere.

Up? It seems that it would fall, or is the plywood under it too?

Do you see any harm in bolting both pieces? Well, probably bolting the
throw-away (no harm drilling through it to do so) and clamping the
"keeper". The hole is near a corner of a fairly large piece (15x20 inch
or so), so it would cause trouble unless it is held in place.

Thanks!

Bill

Bill,

If the thought of what is going to happen to the scrap piece worries you a
lot, mill it close and then twist out the scrap section and then just mill
off the little tits.

When I worked at an injection mold shop, My job was to drill sequential
holes to remove a 6 inch thick slug from a mold base to install inserts.

I would drill most holes right at a center to center distance and then leave
a few with a little larger web to keep the slug from tipping and causing
mischief. I would then cut through the webs with a hack saw and then clean
up the rough edges.


--

__
Roger Shoaf

Important factors in selecting a mate:
1] Depth of gene pool
2] Position on the food chain.



"Bill Schwab" wrote in message
hlink.net...
Bob,

I'd mount the piece to the mill table with the bolt(s) going through the
part to be removed. Put a piece of 1/8" plywood underneath when you do
this
so you don't cut the table of the mill. Plunge in one corner and go
around
the edge of what you want and one pass will do the whole thing. The big
piece will pop up when you have the cut done and really won't go
anywhere.

Up? It seems that it would fall, or is the plywood under it too?

Do you see any harm in bolting both pieces? Well, probably bolting the
throw-away (no harm drilling through it to do so) and clamping the
"keeper". The hole is near a corner of a fairly large piece (15x20 inch
or so), so it would cause trouble unless it is held in place.

Thanks!

Bill

"Bob May" wrote in message
. ..
I'd mount the piece to the mill table with the bolt(s) going through the
part to be removed. Put a piece of 1/8" plywood underneath when you do
this
so you don't cut the table of the mill. Plunge in one corner and go
around
the edge of what you want and one pass will do the whole thing. The big
piece will pop up when you have the cut done and really won't go anywhere.

--
Why do penguins walk so far to get to their nesting grounds?



Bob, that's not a very good way to go about the job unless the opening
desired is just a rough cut, and size or finish aren't critical. It
always leaves a sharp point the radius of the end mill, and generally a
ragged cut with chip welding, even when well lubed.

What works best is to clamp the part to the table, then open the window
undersized, leaving enough material for some finish passes that permit
sizing and locating the window properly. By measuring and marking the
dials, you can machine a close tolerance window easily, with a decent finish
in the window by taking the last cut by climb milling. That pass should
not be much of a cut (a few thou) , so you don't have problems with the
cutter self feeding.

Setting the part on parallels is better than using a (wooden or other type)
spacer, for it permits chips to clear the cutter by dropping through the
slot as it develops.

Harold

On Sun, 23 Oct 2005 03:28:36 GMT, Bill Schwab
wrote:


Back to the serious, I will keep that in mind. In this case, the
work will be too large for the vice, unless I attach something to it and
in turn put that in the vice. By the time I get that right, it will be
easier to remove the vice and use clamps.

Clamp it to the table, with a thick piece of something sacrificial
under it. Plywood, MDF (which I usually use cause its flat)

Gunner

"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner