angle grinder discs

[Don Dougan <dondougan@zzzzzzzz>]

Hi Norman,

This is the short answer to your query about sanding and grinding discs
for right angle grinders . . . :-)

Cheers,
Don
http://www.dondougan.homestead.com/indexdd.html

CUTTING, SANDING, POLISHING WITH RIGHT-ANGLE GRINDERS OR SANDERS

For deep cuts the large right-angle grinder with a 7" SiC  masonry
grinding disc or a 10" diamond saw blade will be a powerful choice.  The
grinders can also be used for sanding with SiC sanding discs mounted on a
flexible backing pad.  The backing pads available are semi-flexible
phenolic, plastic, or rubber.  These tools can weigh up to twenty pounds
and have powerful motors rated up to 15Amps or more.  These grinders have
a relatively high speed (10-15,000rpm) and are much more powerful than
the pneumatic counterparts.
For doing small or detail work a 4" or 4-1/2" SiC masonry grinding disc,
4-1/2" diamond saw blade, or grinding disc fitted to the small
right-angle grinder (weighing only five pounds or so) is more comfortable
to use than its larger cousin.

Optional feature in grinders manufactured for the stone industry is a
water feed.  This feature is usually coupled with a variable speed
switch.  The water-fed grinders are much more expensive than the dry-cut
varieties, but they also work much more efficiently and quickly with
diamond sanding and polishing discs.  Water fed systems require the use
of GFI electrical breaker/switches and proper safety gear ? typically
including rubber boots, apron, and gloves.

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SANDING and POLISHING

ZEC© discs (16 grit to 120 grit silicon carbide) are made for the stone
industry with the abrasive grit molded in a heavy spiral pattern with air
holes and channels designed to cool and exhaust the dust rapidly during
use.

Waterproof Resin Bond Discs (24 grit to 240 grit silicon carbide) with a
7/8" arbor hole are flexible and used for subsequent sanding and
contouring.  Though they can be used dry, the finer grits work much more
efficiently if used wet.

Diamond Discs (60 grit to 3200 grit) are manufactured strictly for the
stone industry.  Initially an expensive outlay, but in the long term much
more efficient and economical than silicon carbide.  All diamond sanding
and polishing discs need to be used with a water-feed system.  The grit
in most diamond sanding disks is attached by electroplating to a thin
layer of metal which is in turn attached to a flexible composite body.
The finer polishing disks eliminate the use of metal and have the diamond
grit embedded in the composite plastic body itself.  The diamond
sanding/polishing accessories are intended only for use in a
variable-speed water-fed tool.

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SAWING/CUTTING/GRINDING

Silicon Carbide Abrasive Cut-Off Blades are made for cutting concrete and
masonry.  They are inexpensive and widely available in both flat and
depressed-center versions.  The blade wears away as it is used, becoming
smaller and reducing the available depth-of-cut.  Though intended for dry
use, and increased efficiency and longer life will result in working wet.

Silicon Carbide Abrasive Grinding Discs and Cup Wheel are made for
grinding concrete and masonry.  They are inexpensive and widely
available.  The wheel wears away as it is used, becoming smaller and
reducing the available grinding surface.  Available both with and without
threaded arbor.  Though intended for dry use, and increased efficiency
and longer life will result in working wet.

Sintered Diamond Saw Blades and Grinding Wheels are made for dry cutting
of all types masonry and stone.  The diamond grit is embedded in the
metal matrix on the edge, and the diamond is only exposed as the metal
itself wears away.  Though the sintered type accessory is intended for
dry cutting, increased efficiency and longer life will result in working
wet.  Available both with and without threaded arbor or faceplate.

Electroplated Diamond Saw Blades and Grinding Wheels are made for dry
cutting of marble and softer stone.  Though the diamond grit is generally
much more heavily concentrated than in the sintered type resulting in a
smoother cut, the grit is held in place by a relatively thin layer of
electroplated metal.  This thin layer is much more subject to wear than
the sintered matrix, so the electroplated-type accessories are intended
for use only on marble and softer stones ? NOT sandstone ? and increased
efficiency and longer life will result in working wet.

*******************************************************
Tungsten Carbide Grit Grinding Wheels in both random and structured-tooth
versions that are made to fit on the right-angle grinder.  Though these
wheels are sometimes advertised as suitable for grinding a variety of
hard materials, they are primarily intended for working wood.  Their use
for stone should be limited to softer varieties (alabaster, limestone,
slate, steatite).  Their effectiveness is limited on harder stones such
as marble because the metal that bonds the tungsten-carbide grit quickly
wears-away with dry-cutting techniques.

*******************************************************
A word about switches:  from personal observation I would have to caution
against choosing a grinder that is equipped with a paddle switch.  Though
in use it is a comfortable I have seen students set this type of grinder
wheel-down on the switch, resulting in the grinder being accidentally
switched-on and creating havoc on the workbench.  Though some pneumatic
paddle switches have a safety that prevents this, I am not aware of any
electric versions that have the safety catch so as to prevent accidental
switching-on of the tool.  A standard trigger switch is my first
preference, with the slide-type switch as a second choice.