Selection Of Chisels; Theory Of Turning - Craftsman 351.221060 Operator's Manual

USING WOODWORKING CHISELS
SELECTION OF CHISELS
Sharp tools are essential for clean, easy work. Select tools that
will t akeand holdkeen edges.
GOUGE SKEW PARTING TOOL
nd f14
SPEAR POINT FLATNI_E ROUND NOSE
Figure g -The Six Commonly Used Chisel Types
THEORY OF TURNING
The two classes of chisels are those intended primarily for
cutting, end chisels used only for scraping.
• The cutting chisels are the gouge, skew and parting tool.
These are the most used. They are commonly sharpened
to a razor edge by honing on both sides.
The scraping chisels ere the f_at nose, round nose and
spear point. These are not honed on the f_atsides - the
wire edges produced by grinding ere lef_ on to aid in the
scraping process.
Cutting Chisel Scraping Chisel
Figure 10
Cutting and Scraping
To cut, the chisel is held so that the sharp edge actually
digs into the revolving work to peel off shavings.
To scrape, the chisel is held at a right angle to the work sur-
face. This tool removes fine particles instead of shavings.
Cutting Scraping
Figure 11
Many operations require that the cutting chisels be used for
scraping, but scraping chisels are practically never used for
cutting. Scraping dulls a chisel much faster, especially the
razor sharp cutting chisels.
Cutting is faster than scraping end produces a smoother finish
which requires less_sanding. However, it is far more difficult to
master. Scraping, on the other hand, is far more precise and
easier to control
When You Can Cut and When You Must Scrape
There are two different approaches:
• One approach is toward a drcumfarence of the workplace (br
example turning down the outer surface of a cylinder or the
inner wall of a hollow round box), In this approach, the surface
being turned l_-avels under the chisel edge like an endless bell
• The second approach is toward the diameter of a workpiece
(as when turning the face of a facaplate turning, or the side of
a large shoulderon a spindle turning). In this approach, the
surface being turned rotates like a disc under the chisel edge.
• Sometimes the optimum approach will be a combination of
both methods.
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Diameter
Approach
Figure 12
Either e cutting or scraping action can be used when the
approach is toward a circumference -the shavingis removed
like a peeling from a potato, Scraping can only be used when
the approach is toward a diameter. The reason is obvious
when you consider that faceplate turning practically always
requires removal of wood across the grain. Wood does not
peel easily across the grain and attempts to use any inappro-
priate cutting methods will fiksiy result in damage to the work-
piece. There is also danger that the tool could be pulled from
the hands of the operator.
In general, a cutting action is used for the majority of spindle
turning operations while faceplate turning is usually accom-
plished by the scraping method. When a combination
approach is to be used, the operator will have to judge, by the
feel of the work, when to stop cutting and start scraping.
Never try to cut when it becomes difficult to hold the chisel
against the roughness of the wood grain.
How to Position Tool Rest for Circumference Cutting
When cutting, the object is to pierce the outer skin of wood to
a certain desired depth and then to hold the chisel steady
with the bevel edge parallel to the work circumference so that
it will peel off a shaving at this desired depth.
• The only sure method of holding the chisel steady is to
rest the bevel against the work (Figure 13A). When the tool
rest is at the proper height, the chisel can be held with the
bevel pressed against the work, and the tool rest will act
as a fulcrum to support the chisel against the downward
force of the revolving work.
If the rest is placed too low, so that the chisel is held with
the bevel out from the work (Figure 13B), the cutting edge
will continue to dig deeper into the work. It will dig in until
the "bite" becomes so deep that your hands have diMcuffy
holding the chisel - then the improperly supported chisel
will begin to bounce or chatter against the workpiece.
ff the rest is placed too low, the chisel must be held
extremely high to position the bevel against the work
(Figure 13C). Then the rest loses most of its value as a ful-
crum and the downward force of therevolving workpiece
tends to kick the chisel back out of your hands.