Re: [VAC] Cutting aluminum

["Dr. Gerald N. Johnson" <geraldj@xxxxxxxx>]

With compound hand snips (left, right, and straight cutting), a hand
nibbler, a squaring shear, a deep throat bandsaw set for cutting metal,
and other fine toothed saw blades for the coping saw and the jeweler's
saw as well as braced back Xacto saw blades, I've not applied the die
grinder to aluminum cutting. For intricate cuts, I generally use an end
mill in the vertical milling machine. Strikes me that the router or die
grinder could do much of the same if guided carefully. Aluminum the
thickness of the Airstream shell or vent lid shouldn't cut any harder
than edging masonite and should trim with the same techniques. Backing,
above and below with scraps of wood will help hold down the noise and
ripping. The same counter top trimming bits would be appropriate. The
tools used for routing dry wall around electrical boxes should be
appropriate also.

There is a great deal of difference in how different aluminum alloys get
along with the cutting tools. 2024 and 6061 machine beautifully but
break before bending in my box brake. 3003 bends beautifully, but
drilling and machining is more like copper, stringy and gummy and leaves
great burrs, even in the milling machine. I prefer to punch the soft
aluminum alloys when I can. Using my hand squeezed hole punches on 2024
takes as much pressure as punching steel.

Its been reported here that 2024 was used for Airstream skins. 6061 is
common for extruded shapes, rods and bars and was used for Grumman canoe
hulls.

Grinding tools that work well on steel are destroyed by grinding
aluminum because the aluminum melts into the grinding wheel. That's a
first rule in most shops, "Don't ever grind aluminum" and the culprit
that ignore that is easily found trying to dislodge the aluminum melted
into the grinding wheel. That wheel has to be ground down to get rid of
the aluminum or replaced which can be an expensive experience for those
that can't follow rules.

Aluminum can be cut with abrasives, but they need to be at slower
surface speeds so the aluminum is not melted. I use a 5" sanding disk at
maybe 3000 RPM for deburring both steel and aluminum without melting.

Dremel does make small circular saws that if their teeth were finer
would cut aluminum adequately. I have a large supply of 3" diameter saws
with fine teeth that work fine for both aluminum and steel. I bought a
couple bushel of used ones once. They take a 1" arbor, made for
horizontal mills I guess. For safe cutting its important that any saw
blade, circular or hand powered have teeth often enough to keep at least
two on the thickness of the metal. Otherwise the saw blade will hang up
on thin stock. Again scraps of wood behind or on both sides of a cut
(and being cut at the same time as the aluminum) can make thin aluminum
cut more controllably. Soft aluminum can be cut with wood saws that way.

One of the features of 2024 is that it gets harder with age. Its an age
hardening alloy.

Gerald J.