Rosette/Circle Cutter – How it’s made by Joe Ulman
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This simple rosette/circle cutter is made by laminating 5 pieces of wood. Start with a block of 1” thick hardwood by roughly 6” long. Slice off 6 pieces with the following thicknesses (inches): 3/8, 3/8, 1/2, 13/64, 1/8, 1/8. The fourth piece 13/64 is the width of the cutter blade, so adjust to meet your cutter.
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I ordered a custom blade from Ron Hock similar to what he makes for LMII’s cutter but a longer version. The extra length helps facilitate setting the depth and makes for easier handling when honing. The 13/64 slice is used to form the wedge slot and also make the wedge (there should be enough extra to make a couple wedges from the cut off).
The 13/64 piece (with the wedge section cut out) is sandwiched between two 1/8” thick pieces. This laminated 3 layer assembly is then cut off to a total length of about 2.1” with the wedge slot roughly centered as shown.
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The laminated 3 layer assembly is roughly 1/2” thick to match the 1/2” center sliding piece. After the laminated wedge slot assembly is cut to about 2.1” long (sorry no picture of this), it gets sandwiched between two full length 3/8” thick pieces.
The main assembly is drilled for a 1/4” bolt and wing nut (two holes spaced about 1” apart seem to give an adequate range of operating radii). The 1/2” center sliding piece is cut to a length of about 3-1/8” and drilled for 1/4” pin (or diameter of pivot pin you will use). Slot for a 1/4” fixing bolt with sufficient slot length for an adequate sliding range; around 2 inches +/-. The disassembled circle cutter:
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Of course you will need to adjust all dimensions according to your own cutter blade, pivot pin, and any other requirements you might have. Assembled cutter:
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It should be noted that a proper workboard is key to the performance of this cutter as the precision and ease of cut is really obtained by the secure fit of the pivot pin in the underlying workboard rather than relying on the soft soundboard wood surface. This also constrains the tool on the vertical axis with no rocking longitudinally or laterally whatsoever and so the cutter blade always travels along a very precise radius. The full depth of cut is set in the tool initially and the cut is easily made in a few successive light passes with the tool providing excellent feedback during the cut.
For a workboard I use 1" MDF that is leveled and a (perfectly vertical) hole drilled that has a very snug fit on the pivot pin. The tool can then be lifted, smoothly sliding up the pin without dislodging it from the workboard, for changing directions of the cut or to check your work and test cuts.
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I also find the small Veritas router plane (shown in picture) works nicely to flatten the excavated rosette channels.
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