On Tue, 5 Feb 2008 17:48:54 -0800 (PST), ayaz said:

i can't decide between diamond and tungsten carbide as suitable
materials for cutting steel. any suggestions?

As a previous poster replied, this depends on the scale and scope
of your enterprise, and what kinds of steel you intend to cut. If
you can provide more contextual information, we can help you more.

That having been said, I like tungsten carbide for cutting steel
in my workshop. Usually I am cutting mild steel, but sometimes
need to grind off the heads of protruding drywall screws, which
are made from ~600BHN (very hard, but brittle) toolsteel. A
tungsten carbide high-speed cutter bit in my 5A (3/4 horsepower)
drill is what I usually use.

A problem I have had with diamond cutting-tools in the past is
that the adhesion between the diamond dust and the cutting wheel
or saw teeth is poor, and my working surface sheds its diamond
coating over time. I have not had this problem with the tungsten
carbide (which is sintered into whole pieces). Possibly I've just
been using low-quality diamond tools, so take this with a grain of
salt.

Some disadvantages to the high-speed cutter bit in a handheld
drill are that I cannot make precision cuts, and cutting is very
slow. A friend has a CNC plasma cutter which cuts up to 1/8"
thick steel very precisely and fairly quickly. If I had the
spare cash (about a thousand bucks for the cheapest models),
I'd get me one of those. I do not know how quickly plasma
cutters wear out, or what they cost to maintain. I've window
shopped some and drooled over several models, but even the high
end plasma cutters seem limited to 1/4" or thinner steel plate,
so one advantage to tungsten carbide cutters is that they can
work through much larger thicknesses. If I had to cut through
an inch thick steel bar, I would start with my WC cutter bit
(which is 1" in diameter with a 3/8" shaft, so could cut to a
depth of 5/16" around the circumfrence of the bar) and finish
cutting the inner part (the remaining 3/8") with a reciprocating
saw with WC-tipped teeth. I've never had opportunity to do
exactly this, though, so I'm being a little speculative.

Another alternative is toolsteel, which is much less expensive
than tungsten carbide or diamond. I don't particularly like
using it, though. I have to take it slow and periodically drip
oil on the working surface as I cut, or the toolsteel loses its
temper and gets ruined (by the time you notice its color change,
it's already too late). It also cannot be used to cut or grind
drywall screws or other hardened steel. If you were setting up
a factory for short runs of stamped mild steel parts from thin
sheet, though, toolsteel stamps could be an economical choice.

I removed soc.zimbabwe from the followups (wtf?), and added
rec.crafts.metalworking -- folks there would know best about
this sort of thing.

Good luck,
-- TTK