There are many occasions where one would want to do some marking on work items, or carving or other decorations. This can be done freehand or with the tool rest, but neither of these are really good for the job. What is needed is a work platform, like this one:
This is simple to make. You’ll need a piece of 18mm plywood (do yourself a favour and buy the good stuff), some 8mm threaded rod, 4 normal nuts M8 (also possible: furniture nuts, those are the ones with cramps on a ring around the threaded bit), 4 wing nuts M8 and 4 washers. My work platform is square, with two quadrants sawn away to accommodate working around bowls or other round shapes.
It is mounted on a Robert Sorby tool rest (available from Axminster or the Tool Post or many other sources), like this:
The easiest way to make the mounting brackets is by cutting rectangles about 60mm x 50mm, also from plywood. Mark a line 20mm parallel to a long side and a centre line. Drill the holes for the threaded rod (find the halfway distance between the centre hole for the tool rest and the outside edge) and then drill the hole for the tool rest. This hole has to be a tight fit. It’s probably best to drill a little smaller (I used a Forstner bit) and then use a round rasp or file to widen it until the tool rest just fits in. You want the maximum amount of surface gripping the tool rest.
Now mark the pieces with numbers or letters, so you know which belong together and which sides should align. Then cut along the 20mm line, and clean up the cut surfaces. This alone should provide enough clearance to allow to grip the tool rest when the wing nuts are tightened.
Now work out where you want the support to be located underneath the table. I have put it about 25mm sideways from the diagonal line in one direction, and centered in the other. Mark the positions of the clamping blocks, and then drill the holes for the threaded rod. Note: the rod absolutely has to go through the main platform, as otherwise you rely on the glue alone to hold it in place. Now counterbore these holes on the other side just deep enough for the nuts to sit under the surface.
Now you can assemble the whole thing. I have glued the smaller clamping blocks onto the plywood, with the rods inserted. When this glue is dry, you can glue in the rods with the nuts fitted at the top. I have used high viscosity (thick) superglue for this, but wood glue will probably also work. Obviously the rods have to be long enough to allow fitting of a washer and wing nut.
This platform is very flexible. It can be moved anywhere the banjo will go, and you can swivel it to quite extreme degrees. I have found that in order to hold it properly I had to tighten the wing nuts quite heavily.
Now you have a platform for marking, carving, milling, etc. In combination with the disc sander this can also be used as a sanding table.