Ed Huntress wrote:
"Martin H. Eastburn" wrote in message
...
Harold and Susan Vordos wrote:
"Martin H. Eastburn" wrote in message
.net...
I think we need to think about this a little.
Diamond cutting tools are steel based and cut steel HSS and carbide
drills and mills. Perhaps there is transference, but not all that
much ?
Martin
They may do that, but are they recommended for the application? Dunno.
I've never used diamond turning or milling tools. If so, do they
recommend
specific speeds, to keep the temperature down? That's the critical
point.
I'm not convinced I'm the right person to answer the degree of transfer,
but
for diamonds that rely on sharp corners to do their work, it takes very
little to change them appreciably. Iron has an affinity for carbon,
and it
isn't proud where it gets it. Up to the point of saturation, so long
as
the temperature permits transfer, it will absorb it. That tells me
that
prolonged contact at high temperature, iron could literally absorb a
complete diamond.
It's not a heat thing alone, nor is it an iron thing. Diamonds will
withstand soldering (re-tipping prongs, for example) with no ill
affects,
and they can withstand a constant dressing of aluminum oxide or silicon
carbide wheels, even large ones such as are found on centerless
grinders.
They are often 24" in diameter and 8" or more wide. Heat isn't a
problem,
but combined with iron, it quickly becomes one. That's about the
extent of
what I know, and from experience, I know that contacting diamond wheels
with
iron (steel) is a mistake. The typical diamond wheel feels as if it's
been
greased once steel has been applied. Sorry I'm not more help.
Harold
Diamond is typically grinding and sawing. Sapphire is and Diamond I
believe used
in exotic sharp edge cutting of plastics and glass. Typically both
fracture
under load if not supported.
Since the diamond is best in conduction - your hand on the far side of a
thin diamond
window would feel almost all of the heat on the other side - so when the
tool tip gets hot,
it conducts to the base metal - steel and flows off - cooling the diamond.
Continuous heat addition (at one spot ) (as with a flame or arc) would,
but a turning
tool and the conduction prevents this. Also the typical use involves a
flood of water
based coolant.
Martin
I'm not sure what you're saying here, Martin, but diamond turning and
milling cutters are not used on ferrous metals except in very rare
situations. They just don't last, for the reasons Howard has explained.
In production, diamond is use primarily on high-silicon aluminum. Other uses
include composites, plastics, glass, and other non-ferrous metals.
The development that made polycrystalline synthetic diamond a near-necessity
in production was the use of very high-silicon (hypereutectic) aluminum
casting alloys in automotive applications. Another one of the early users
was Mercury Marine, who used it for machining their hypereutectic outboard
motor blocks. OMC soon followed suit.
--
Ed Huntress
Ed - I generally agree. But I feel the panic is a bit high.
A diamond on a metal base that is spinning contacts the work for a very very short period
of time. This assumes the tool is spinning and the diamond isn't massive...
I'm assuming a 'point' of fine atomic level that diamond can do. It is the touching / grinding
on a fine point. [ remember the Garnet sanding sheets that shatter as they impact and stay sharp ]
diamond is tougher and stands up to higher pressures.
The 'nano'-second it touches the work it will heat up but starts to cool down as the cutting arc
is swept. The diamond wicks the heat (being the best conductor - far better than metals) to the
work base metal the diamond is loaded into. Which gets hot. (a little anyway).
If coolant is supplied as in mills this would help.
Normally diamond is to expensive to use in a normal work area, other materials have been developed.
Even special process of near zero degree work has been developed for some applications.
Saw blades have diamond pressed into slots on the circumference. These slice through rock and cements...
I have sliced through tons of material. The diamond doesn't absorb into the host material (the tool)
but I suspect the very highest temps are only at the tip where atoms are stolen.
Is it simply a matter of cost ? - the carbon is absorbed a little and the tool becomes used up?
Maybe the data is simply old economics. Diamond drill heads bore through iron cobalt deposits and
other iron rich layers for many years in well drilling. So maybe research needs to look at this
again with a different point of view.
Martin
--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder