Sharpening Made Easy - Knife Sharpening Information and Equipment
Harvesting Celery in
"The Salinas Valley is in Northern California. It is a long
narrow swale between two ranges of mountains and the Salinas River
twists up the center until it falls at last into the Monterey
Bay." - John Steinbeck, East of Eden, (1952)
"The Carmel River is a lovely little river. It isn't very long
but in its course it has everything a river should have."
-John Steinbeck, Cannery Row, (1945)
Webpage revised November 20,
For the past two years I have been consulting with a vegetable
grower in Salinas, CA on improving the sharpening methods used in
the fields. Currently a vegetable cutter will spend up to an
hour thinning and sharpening a new knife before using it in the
field, then he will spend several minutes sharpening it at each
break every day. Sharpeners used range from stones to files to
steels. My client wanted to reduce this labor for the
harvesters and produce a sharper, more consistent edge. A
fringe benefit would be to reduce the cutter's resistance to using
stainless steel knives. Stainless knives are being encouraged
by the Ag. Dept., but the cutters realize they are more difficult to
The Salinas Valley sits between the Gabilan mountain range on the
east and the Sierra de Salinas hills on the west. Up the
valley the Sierra de Salinas peter out and the valley widens over to
the the San Lucia mountain range. The Salinas River flows
northerly through the valley 150 miles to the Monterey Bay. US
101 roughly parallels the river through the valley. Most of
the farm land is in the wide northern section of the valley between
San Lucas and Castroville, while the southern end has many
vineyards. Salinas, a city of 150,000 and seat of Monterey
County, is 20 miles east of the city of Monterey. Seen from
the air the valley is a mosaic of fields that produce fruits and
vegetables from artichokes to zucchini. Okay, zucchini is an
exaggeration, but overall it is the nation's top vegetable and wine
grape producing region, and leads the world in seed technology,
growing and harvesting methods, and processing technology.
While we also worked on head and romaine lettuce, broccoli and
cauliflower, the celery knife was the most challenging.
A celery field being harvested.
First the celery stalk is cut from the root, then the root
end is trimmed.
Then the stalk is cut to length.
Harvesting up to 3000 stalks a day, the cutter makes between 12000
and 20000 cuts. The cutters (below, left) pass the stalks to
the packers (center) where they are washed, wrapped and boxed
(right). The boxes are put on skids and loaded on
trucks. With all the processing done in the field, all that
remains is refrigeration and shipping. The harvesting machines
are 50 ft. wide and cover 12 to 16 rows, and 100 ft. machines are in
development. Each crew has 12 - 16 cutters and an equal number
of packers, plus drivers and handlers.
Some crops, like cauliflower and broccoli, are harvested with
butcher knives, and even the lettuce knife is not that much
different. The celery knife, below, is unusual. It
evolved just for this crop, and is not used for any other. The
tip is rotated 90 degrees and angled for cutting the root.
Although these knives have been made from scratch, most are made by
cutting and welding butcher knives as below.
It has two sharp edges, the tip and the side. Here one cutter
is sharpening the edge while another is sharpening a well worn
tip. The top side is ground flat while the bottom side is
convex - a sort of modified chisel grind.
Our challenge was to find a sharpening method that could be used in
the field. Another consultant from the meat packing industry
walked away from this because the farmers did not have a sharpening
As I mentioned, stones, files and steels were being used and, in the
picture above, a salvaged industrial grinding wheel. Electric
power was available of some of the harvesting equipment, and my
client was willing to add a generator to the others. We
experimented with a variety of sharpeners - slot devices, wet and
dry grinders - an finally settled on a belt sharpener after it was
observed that the small motor could be replaced with a 12V motor and
used right at one of the trucks in the field. The other
advantages of a belt sharpener are that belts are easily changed,
and there is both a straight section for flat bevels and a slack
belt section for convex bevels. We bought a small motor and modified
ours that same day. It turned out to be under powered and the
sharpener we were using is no longer available, but it got us off to
a good start.
Our next design was a Koval Knives' Little Sharpie modified
with a large 12V motor. It was more powerful and heavier than
we needed. We based the final design on a low cost 1" x 3"
belt grinder. The right size motor and a special drive
pulley gives the proper belt speed, and a new base allows operation
in the horizontal position. For more details, see field.htm
Cutters like their knives to be very thin and sharpened to a 15
degree single bevel (chisel grind). The initial preparation of
a new celery knife, taking off the original double bevel, thinning
and sharpening, took about an hour manually. With this
sharpener it can be done in under 5 minutes. Sharpenings
throughout the day take just seconds. Our project has been a
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