Recently my 12-year-old son, Alex, was busy working on his
sixth-grade project-the tools of early man. But I am not
sure that early man would have used my bench grinder, as
Alex did, to fashion an axe head out of a piece of field
granite.
Leonard Lee, an Ontario, Canada, toolmaker, author and
one-time farmer, says the bench grinder might be the most
abused tool in any workshop (Alex's work defining ultimate
abuse). But a well-maintained, vertical-wheeled,
double-spindled dry bench grinder is an inexpensive tool
($35 or less) that will give other tools lasting edges.
Lee is the author of "The Complete Guide to Sharpening," and
he offers the following suggestions for keeping your bench
grinder in top shape:
Choose the stone
Grinding stones 6 or 8 inches in diameter
have various characteristics. Depending on the sharpening
job, you'll want to consider abrasiveness, grit size, the
stone's grade or hardness, and its structure or grain
spacing.
Also important is bond, which describes the way particles on
the wheel are held together to form the stone. If the bond
is too solid, the surface of the stone will be worn smooth
quickly and its abrasive capacity will diminish. If the bond
is too fragile, the wheel will wear quickly.
Lee is not impressed with the stones sold with most
grinders. "(They) make good patio stones," he suggests.
"Farmers want a stone to last a long time, and these will.
But they ruin a lot of tools without knowing it."
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Get a tool rest
Buy or build a free-standing tool jig,
which will perform two functions. It will clamp the tool at
the angle needed to restore the cutting or working angle.
And a good clamp will allow left-to-right movement across
the face of the stone as you remove material from the
tool.
Make the wheel round
You may find that the tool being
sharpened jumps off the grinding surface of a new stone.
You'll want to remove these high spots by "truing" the
stone, or making it perfectly round. Purchase an abrasive
truing stick.
A better choice is a diamond dresser-a steel, pencil-shaped
tool with a diamond tip. It is clamped into the tool jig and
rotated down 10 to 15 degrees below the center line of the
wheel. Never clamp the dresser less than 5 degrees below the
center line or it could get damaged. Put the tip of the
dresser on the highest point of the wheel, turn the grinder
on and slowly move the dresser across the face of the
stone.
Truing is a gradual process, and each cut should not be much
more than the thickness of this page. After each cut, raise
the tool toward the center line to further reduce the high
points. If the wheel is still not round after you've reached
a 5-degree down angle, reset the dresser below 10
degrees.
Avoid glazing
This is not a desirable condition for your
grinding stone. Glazing is a result of misuse, such as from
grinding aluminum or brass. It severely affects the ability
of the stone to restore an edge to a tool.
A star-wheel dresser (some also come with diamond cutters)
is used to restore a stone's cutting ability. By running the
star-wheel dresser across the turning stone, you will
restore a coarse, aggressive surfacing to the grinding
stone.