Cutting sheet steel

In article ,
(Dan Thomas) wrote:

(Veeduber) wrote in message
...
One of the easiest ways to cut sheet 4130 is with a band saw. Use an
old metal cutting blade installed upside down (the teeth pointing up).
Run the saw at normal speed and feed in the material. Keep the
pressure up and it will go (melt) through like you are cutting butter.
Don't pause though, it is not so easy to get started again. Some have
also used the back side of the blade for this purpose with success.

O-ring Seals

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Dear O-ring (and the Group),

I believe you'll find there's a bit more to it than that :-)

First off, the 'normal speed' you're referring to is for a woodworking
bandsaw.
The down-side is that most woodworking bandsaws are fitted with a rubber
'tire' on their driver- & idler-wheels. Friction cutting steel (which is
what
you're doing) will destroy the tire on the driver-wheel in short order.
Bandsaw tires are moderately expensive and can be hellishly difficult to
replace on some saws.

Metal-cutting bandsaws do not use tires. The wheels are sizes so that the
teeth overhang the edge of the wheel, not only for cooling but for clearing
the
swarf.

You can set-up a metal cutting bandsaw for friction cutting if you have the
proper ratio pulleys (ie, increase the blade speed).

The popularity of this method hinged largely on the builder's ability to
splice
their own blades because the original idea was to use common steel
strapping.
Operated at high speed -- and cutting relatively thin stock -- the stuff
does
in fact cut like butter, with a very attractive displace of sparks, too :-)
But the strapping was rapidly consumed and unless you were a dab hand at
splicing, ideally with a Do-All type butt-welder, there was no long-term
advantage over regular cutting.

All of this came about due to the difficulty of cutting relatively hard
steel
in thinner gauges, which loves to strip the teeth off anything. .035 4130,
you
can do pretty well using a regular bi-metallic 32T blade by simply rigging
the
work to feed 'downhill' so that two teeth are in contact with the work.


I used to cut 4130 using the bandsaw method, with a 1/2" bimetal
blade installed the right way, and just letting the teeth round off
the first time I used it. It would cut rather nicely, and didn't hurt
the rubber tire. Keeping the cut straight was the biggest hassle.
There's a German-made friction-cutting tool designed to cut sheet
of all sorts using a steel wheel that doesn't spin but instead
oscillates at a fairly high frequency in an arc of about 20 degrees or
so. I saw it demonstrated on aluminum, steel and even stainless steel.
Really noisy, but a really clean cut, too. No chips. When the section
of the disc doing the work gets a bit dull, you loosen the screw and
rotate it a bit to a sharper section. I am trying to remember the
name, but can't. It was a big hit at our aircraft engineer's symposium
a couple of years ago. Not cheap, but well worth the cost if you're
doing much cutting.
Friction welding of aluminum aircraft skin was presented there,
too, though not demonstrated. Skins are butted together and a
high-speed carbide bit with a flat end and one raised tit are run over
the joint under pressure, the metal heats and fuses, and the alloy is
not affected so strength isn't hurt at all. I don't know how. You get
a flush, seamless joint with far less hassle than riveting. Also very
expensive. I think Airbus is using it on the A380, maybe.

Dan

Dan

I would think that the seam would lose a lot of its basic heat treat
strength, due to the melting/recrystallization.