"Vernon" wrote in message
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On Oct 22, 11:22 pm, "Ed Huntress" wrote:
"Vernon" wrote in message

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What are they good for? I just don't get it although I've done my
homework and have even consulted wikipedia, that ultimate authority!
I understand they will grind down a surface in infinitessimally small
increments and produce a beautiful surface. But on what?

On anything you want to grind flat. g

And why? V

Most of their commercial use is in the tool and die industry, where
they're
used to make extremely flat surfaces, to extremely accurate dimensions.
It's
also possible to use a shaped wheel to cut 2D contours and grooves.
Multi-piece blanking dies are sometimes made from sections ground on
surface
grinders, with several pieces making up a complete internally contoured
shape. With special fixtures, they can be used to cut complex shapes like
those on cutting tools.

The materials they cut in those applications are mostly hardened tool
steels
of all types. But they can be used on anything you'd care to grind. With
diamond wheels, you can cut carbide and ceramics.

It's not a primary home-shop tool but they're darned handy, if you can get
one for a reasonable price that's in good condition. Their bedways
(generally roller type) are protected against grinding grit but the way
covers and other protective devices may be shot on an old one, in which
case
the ways can be in very bad shape.

--
Ed Huntress

Thanks. "Tool & Die" making is something I know is "out there" but
have only the haziest notion of what it is. V

It's a high-class end of metalworking manufacturing. The term is a broad one
that includes all of the production tooling made for high-volume metal
stamping and blanking, bending and forming, forging, die casting, and (the
biggest part of it these days) moldmaking, which is the making of plastic
injection molds. These tools are made mostly of exotic alloy steels,
hardened, or sometimes of tungsten carbide. A die set for making some
high-volume product can cost upwards of $100,000. For stamping car body
parts, the tools can cost many times that much. When a car model changes and
the panel is no longer used, the tool is scrapped.

Surface grinders are used to square up those blocks of steel on the smaller
tools, which is the primary part of the business, and to grind various
features on the tools. Some of their functions have been replaced by hard
milling and electrical discharge machining (EDM), and there are other types
of grinders, such as CNC profile grinders, that replace some work that was
once done on surface grinders. But surface grinders are still essential
machine tools in any tool, die, or mold shop.

FWIW, some custom gages for measuring manufactured parts are also made in
those shops -- a specialized type of t&d shop, usually, called a gage shop.
Custom gage making is considered to be a part of the tool-and-die business.
("Gauge" is usually spelled "gage" in this business, when it applies to a
tool made for measurement.) A part of the t&d business that used to be one
of the largest, making jigs for drilling and fixtures for production
milling, has declined sharply with the advent of CNC.

Toolmaking often requires accuracies measured in millionths of an inch. It
requires specialized training for commercial work. If you added up the
output of all of the tool-and-die shops in the United States, it would
barely make it to the Fortune 500. But it's the cornerstone of
manufacturing, having a huge leverage effect on the manufacturing industry.

The Chinese are still not very good at it, with a few exceptions. d8-)

--
Ed Huntress