Tmate
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- U.S. Maryland
I built a pantograph shape cutting machine back in 1979 for use in cutting our frame brackets and motor mounts for car projects. Fast forward 40 years, and I built another one using extruded aluminum instead of steel for a frame. Below is a photo of the original machine (which I still have), and one of the newer version. The first pantograph shape cutting machine (in the U.S.) was invented in 1917. They were the only way to go for 40 years or so.
Pantograph machines can cut simple shapes just as smooth as a CNC machine. They use a knurled, magnetic rotor traveling around the perimeter of a 1/8" or thicker steel template. The torch tip, directly below, duplicates the shape in steel. A slight size adjustment in the template must be made to offset the diameter of the tracing rotor. The formula for an external shape is to make the template smaller by 1/2 the diameter of the rotor minus 1/2 of the kerf, or gap created by the torch. The opposite is true for internal cuts. They can cut straight lines using a straight edge for a template.
Since the steel template is just as difficult to make as the part being duplicated, the process is most useful for reproducing multiple copies of the same shape. One-offs can be cut by using a wooden template, and holding the knurled rotor (a rotary burr) against the edge of the template, changing the direction of manual pressure as it goes around corners. Internal shapes can be cut by using a template with the desired internal cutout. The motor shaft is moved to the inside of the template, and the magnetic rotor then placed back on the motor shaft. Starting at the edge of a drilled hole simplifies the operation.
Both my initial machine and the newer one use small gear motors powered by a model railroad transformer. The magnetic tracer consists of a rotary burr with a couple of iron boron magnets stacked on top pancake style. The reflector plate on top of the magnets adds about 40% to the magnetic attraction. I no longer use these guys, but can't bring myself to get rid of them.
Photo 1 - Original machine built in 1979 for use with oxygen-acetylene
Photo 2 - Machine built in 2019 using extruded aluminum for its frame.
Photo 3 - Magnetic tracer
Photo 4 - First successful shape cut out in 1979 (which I still have)
Photo 5 - Some more pantograph cuts (small holes were drilled).
Pantograph machines can cut simple shapes just as smooth as a CNC machine. They use a knurled, magnetic rotor traveling around the perimeter of a 1/8" or thicker steel template. The torch tip, directly below, duplicates the shape in steel. A slight size adjustment in the template must be made to offset the diameter of the tracing rotor. The formula for an external shape is to make the template smaller by 1/2 the diameter of the rotor minus 1/2 of the kerf, or gap created by the torch. The opposite is true for internal cuts. They can cut straight lines using a straight edge for a template.
Since the steel template is just as difficult to make as the part being duplicated, the process is most useful for reproducing multiple copies of the same shape. One-offs can be cut by using a wooden template, and holding the knurled rotor (a rotary burr) against the edge of the template, changing the direction of manual pressure as it goes around corners. Internal shapes can be cut by using a template with the desired internal cutout. The motor shaft is moved to the inside of the template, and the magnetic rotor then placed back on the motor shaft. Starting at the edge of a drilled hole simplifies the operation.
Both my initial machine and the newer one use small gear motors powered by a model railroad transformer. The magnetic tracer consists of a rotary burr with a couple of iron boron magnets stacked on top pancake style. The reflector plate on top of the magnets adds about 40% to the magnetic attraction. I no longer use these guys, but can't bring myself to get rid of them.
Photo 1 - Original machine built in 1979 for use with oxygen-acetylene
Photo 2 - Machine built in 2019 using extruded aluminum for its frame.
Photo 3 - Magnetic tracer
Photo 4 - First successful shape cut out in 1979 (which I still have)
Photo 5 - Some more pantograph cuts (small holes were drilled).