Working of a Flat Surface, Cavetto, Cyma Recta, Ovolo, and Fillet
The process of carving this sign base begins with the creation of a flat surface. A 1/2" chisel is used to protect the lines, and the end is worked down to the finish level. After setting the depth, the 2" chisel is used to remove mass from the clawed surface. The purpose of the claw chisel is to simply remove large portions of the stone while maintaining an even surface. It is important to note that this particular section of stone is on an angle that is to be worked through the entirety of the section. Once the mass is removed, the finished level can be achieved and tooled with the 2" chisel.
Once
the top section was tooled with the 2” chisel, focus was turned to drawing the
lines for the return section of the stone.
The return is 5” in length and 4” deep.
These lines were then transferred down the front and side of the stones
and scribed. Applying the template to
the newly created return is the next step in the process.
The
template is applied using the scribe as a guide that ensures the edges line up
accordingly. A new profile will appear
on the side of the stone that represents the switchback of the return. When the profile looks to line up properly,
it is then scribed and penciled. Working
the return can be a little tricky, but the process begins by placing the stone
on its back and working the newly created return lines with a 1/2” chisel. It is important to work away from the line,
and work all the way through in a back and forth v –shaped pattern. The inside groove of the v–shaped pattern
should always be deeper than the outside so that the stone is released and does
not pluck when pitched from the outside.
With
the stone worked through along the return lines, it is now ready to be pitched
from the outside. The pitcher is held at
a fairly straight angle and struck with a hammer. Aside from a punch, the pitcher is the only
chisel that is struck with a hammer.
Stone mass is removed and the lines are protected with the 1/2” chisel.
The next step in the creation of the return is use the punch to remove mass after pitching. Punching is normally done in horizontal bands with little spacing in between. This action releases the stone and prevents plucking. After the stone is punched to the satisfactory level, the area is ready to be brought to a consistent plane by the claw chisel. Clawing takes the stone down to just above the level that is created by protecting the lines. As previously mentioned, the 1” chisel is used to bring all of the lines down to the finished level and flattened with the 2” chisel.
The next step in the creation of the return is use the punch to remove mass after pitching. Punching is normally done in horizontal bands with little spacing in between. This action releases the stone and prevents plucking. After the stone is punched to the satisfactory level, the area is ready to be brought to a consistent plane by the claw chisel. Clawing takes the stone down to just above the level that is created by protecting the lines. As previously mentioned, the 1” chisel is used to bring all of the lines down to the finished level and flattened with the 2” chisel.
Now
that the return section is flat and the template is scribed, a line is drawn on
an angle that divides section. This line
is then pitched on the angle, which allows the cyma recta, fillet, and cavetto
of the profile to be worked. The process
of protecting lines, punching, clawing, and finishing is repeated so that the
sloped area is transformed into a flat surface.
Creating
the bottom fillet begins by working the 1/2” chisel away from the top line at a
slight angle. The lower line is then
worked flat and straight. Once the top
and bottom lines are protected, the open edge of the fillet is then worked flat
to the line. This is also done at the
other end of the fillet and connected with the 2” chisel. Mass is then removed from the center by working
the 1/2” in staggered levels that releases the stone with each pass. Finishing of the fillet requires the 2” to be
worked from top to bottom, which creates a sharp 90 degree angle.
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| Nearly completed return |
Creating a Flat Surface
on Stone
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| Flat Surface on Texas Limestone |
The
stone used this semester for learning to create a flat surface was Texas
limestone which is fairly soft. Large,
machine cut stones were split using plugs and feathers and marked with the
desired measurements. Lines were then
scribed and penciled (Picture 1) and a pitcher was used to remove material in
bulks (Picture 2). The stone was pitched
just above the measurement line by holding the pitcher at a fairly straight
angle and keeping it on a consistent plane.
Once
bulk material was removed using the pitcher, the line was protected with the
1/2” chisel. The punch was then used to
remove more material. It is important to
keep a consistent angle with the punch to avoid going under and the punch was
also worked in straight lines with each run fairly equal in distance from the
other. The purpose of the punch is to
relieve tension to prevent the stone from plunking when removing material with
the claw.
The
next step in creating a flat surface in stone is working the claw chisel over
the punched area of stone. This removes
material less material than the punch, but creates a more uniform that is
closer to the desired flat finish. It is
important not to work the stone all the way down to the line but rather use the
line a depth gauge to keep a constant angle when working the claw. Once the material is brought down with the
claw, the ends of the stone are brought down to the line with the 1/2” and
leveled with the square. The 1/2” is
then used to connect the lines on the sides of the stone to create a fairly
flat surface will protecting the line.
Finally, the 2” chisel is used to flatten the surface. The clawed area is brought down flush by
using the protected line as a guide. It
is important to push the same wave across the length of the stone to produce a
uniform finish.
Creating a Stone Template
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| Side View of an Ovolo |
Creating
a template is one of the most important steps when working stone. The template must be drawn and transferred
accurately to ensure that the new addition transitions smoothly and with the
existing stone element. For our ovolo
template, an existing section of stone containing an ovolo was traced using
tracing paper. The outline of the ovolo
was taken to a drawing table and transferred to Bristol paper by using a
compass to place pin holes in on the paper to mark key measurement points. Once the outline was transferred to the
Bristol paper and its design was accurate, cardboard that would form the final
template was cut and the ovolo outline transferred once again. There are several methods to transfer an
outline to the template material, but for this project, the compass method and
taking measurements from the source were predominantly used. As another example of how to transfer an
outline to a template, the outline could be cut out and traced onto the
template material.
After the outline was transferred to
the card, a razor knife and straight edge were used to cut out the
template. It is very important to make
slow, steady cuts when cutting out the template so that it will be as accurate
as possible. Once the template is cut
out, a felt tipped marker was used to outline the exposed surfaces of the
ovolo. These markings tell the stone
mason that the marked areas will be exposed and must be tooled to create a
pleasing finish. The template is then
transferred to the stone that it was designed for and scribed.
Cyma Recta Template
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| Cyma Recta Template |
Zinc was the medium used for the
making of the cyma recta template. The
cyma recta was drawn out on the sheet of zinc, and rather than using tin snips
to cut the template, a scribe was used to basically scratch through the zinc
far enough for the outline of the cyma recta to be seen on the back side. Tin snips are a good tool for template
making, but because of the accuracy required for this template, the scribe
method was the best option. The outline
of the template is scribed until is can be seen on the back side of the zinc;
tin snips can then be used to start the cut, but the profile can be pull back
and for by hand or pliers until it snaps free.
Files are then used to dull the edges of the metal to avoid cuts and are
always pushed or pulled away from edge to remove any burs that may be
present. Zinc was chosen for this
template because it was going to be used multiple times and cardboard would not
withstand the wear and tear of multiple uses.
Carving an Ovolo
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| Side View of an Ovolo |
The
ovolo template was aligned on stone and scribed along with the transfer of
lines along the length of the stone. In
order to make sure that the template was line up properly, the scribe was used
to tap the template in to the right position.
The combination square was then set to 45 degrees as seen in figure 2 to
set the angle to be pitched so that the ovolo could be worked later. The next step was to position the stone so
the 45 degree line could be pitched to remove bulk material and the line was
protected with the 1/2” chisel.
Once
the stone was pitched and the line protected, the mass was removed with the
punch and hammer like previously mentioned in the flat surface section. The surface was then worked flat by the claw
and 2” chisel. Figure 4 shows the
extension of the line for 90 degree fillet and the points of ovolo found by
using the bevel angle. The 1” then used
to remove the mass from the triangle peak created by the flat surface of the
ovolo and 90 degree by working down straight down the center. Once the mass was removed, the 1” was worked at
an angle down each side line and then down the center once more to get down to
the line.
The
process previously mentioned was repeated on the other side of the ovolo to
create a series of flat, triangle surfaces that allow the ovolo to be worked. After these steps were completed, the lines
were protected and worked with the 1/2” chisel.
This was a rather tricky step because of the down and inward angle
required for the 1/2.” The corner of the
90 degree was started carefully and carried along the length of the stone
staying just off of the top line seen in Figure 5. The bottom line was then worked at flatter
angle and the process was repeated until the line scribed line of the 90 degree
was reached. It is important to level each end of this section down the line of
the ovolo so that the depth is set and the chisel doesn't go below the
line. Following this process, the 2”
chisel was used from the side and down from the top to create a sharp 90 degree
on both sides of the ovolo.
Once
the 90 degrees were worked, a dummy and 2” chisel were used to work the
ovolo. The stone was position so that
the ovolo could be worked down from the top on one side and up from the bottom
on the other. It is essential to have
the 2” at the proper angle during this process so it is not skipping over the
top of the stone and not going too deep which would create low spots in the
ovolo. This is the main reason that the
dummy is used because it provides more control than the mallet. The process of working the ovolo in two
directions was continued until a uniform surface was produced.
Process of Using the Angle Grinder and Spinner
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| Using a Spinner to Create a Flat Surface on Indiana Limestone |
When large masses of material need
to be removed quickly, the angle grinder is the best suited for this task. We used a gas powered saw to cut Indiana
limestone into sections that 24” long by 8 to 10 wide in order to speed up the
process rather than using plugs and feathers.
The stones were measured, squared on four sides, and scribed before
using the gas saw to cut the stone. In
order to cut through the entire stone, one side was cut to the maximum depth
that the saw would allow and then flipped over to complete the cut. Water was also used to cool and flush the
stone keep prevent the saw from jamming.
It is important to remember to slow down when nearing the edge of the
stone because the saw is so powerful that it will want to run forward if the
edge is cut too quickly.
The angle grinder can be used much
like the gas saw, but it cannot cut as deep or as quickly. We used the angle grinder to cut a 45 degree
angle when working the cyma recta in Indiana limestone. Much like the ovolo, the 45 degree was
scribed just above the peak of the cyma recta, and was then position so that
the cut line was pretty much straight up and down. A cut at a depth of 1/4” to 1/2” was made
straight down an across the length of the stone. The grinder was held at angle to cut as
deeply as the blade would allow. The
grinder did not cut all the way through but was deep enough so that a hammer
and pitcher could strike both ends of the cut followed by hammer strikes along
the face of the cut to pop of the mass.
It is important to allow cut the top and bottom lines on the stone with
grinder rather than trying to pick up the lines on the sides. This reduces the number of cuts as well as
increases the accuracy. Dust masks,
glass, and ear protection are Always to be worn when using any of these
power tools.
Spinners are used to increase
production when working a stone flat.
While chisels are effective, the spinner is much faster and less energy
demanding. The spinner is worked in a
circular motion across the area of the stone that is needed to be flat. It can be a little nerve racking at first,
but as long the middle of the stone is not work too deeply, it is a very
efficient method to use. Along with the
spinner, a smaller 5” grinder can be used to remove smaller masses of stone and
even flatten areas if handled with care.
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