A cardboard disc sander is a very useful tool. One uses the side or large flap of a fairly rigid corrugated cardboard box. Make sure it has not been bent or creased to damage its rigidity. Make sure one side is smooth. The disc will be placed onto the tapered mandrel of a polishing machine.
One begins by measuring the distance from the middle of the tapered mandrel to the closest part of the polishing machine or its hood with dividers. The dividers are closed slightly so that the disc clears all parts of the polishing machine and hood when rotating.
Remember that a cardboard disc will tend to ride up the mandrel so give sufficient room for this. One then scribes the appropriate sized circle onto the cardboard making sure that the center hole actually penetrates the cardboard.
The disc is now cut out carefully with an X-acto® knife. Remember that most injuries in art schools are from X-acto® knives and do this carefully.
Then one takes a piece of 220 grit emery paper, spreads rubber cement (not white glue-it dries in lumps and ruins the tool) onto the slightly corrugated side of the disc, places it on the back side of the emery paper and turns it with some pressure from the heel of your hand so as to evenly spread the rubber cement on all surfaces to be joined.
The disc is lifted off and fanned over the emery paper so that both surfaces become tacky, dull and mat. The two surfaces are then pressed firmly together and smoothed to effect a good join.
One then trims the emery paper flush to the cardboard disc using a knife or scissors. Keep it close to the cardboard. 3M® has a 100 grit aluminum oxide paper that outlasts anything else. I have seen one sheet last through a whole workshop of hammers and chasing tool refinishing.
Wearing safety glasses the disc is now placed onto the mandrel while it is spinning so that it rides up to the third or halfway level on the taper, piercing through the emery paper. Get your hand off and away from the rotating disc quickly as any emery paper sticking out past the cardboard can inflict what might feel like the worlds worst paper cut. One holds the back end of a steel file or another piece of steel onto the edge of disc and paper to trim off any overlap and make the edge safer. The motor is now turned off and the disc removed.
The area around the center hole is now strengthened by melting a hard file-a-wax or other wax around the center. If one quickly places a torch onto it and removes it the wax may melt and run into the cardboard about the center making the hole last longer in use. If using wax make sure it is dry and set before use as otherwise a vertical spray of wax occurs when the disc is turned on. Better than wax is 5 minute epoxy which can make a very permanent strengthening support. If using epoxy let harden before replacing on the mandrel. With epoxy one can also place a little mesh circle around the center to provide a little more rigidity.
When in use there are a number of cutting speeds available depending upon how close one is to the spindle; further out is faster: closer in is slower. Within a very few minutes there are also a number of grits available as the more used parts of the disc become finer so that one has a lot of choices in speed and grit size all on the same tool and accessible with a minimum of hand movement. To stiffen the disc while it is running one can hold a piece of wood behind it on the paper side while it rotates so as to obtain a more rigid surface for faster flatter cutting.
The tool is used to sand flat surfaces onto jewellery replacing much more expensive jewellers .i.laps;. It is unsurpassed for reshaping commercial and handmade chasing tools and hammers. One can go directly from this sanded surface to a polishing buff. On steel one uses Fabulustre® on a buff and the process of completely refinishing a hammer can be reduced to five minutes or less.
It is absolutely essential that the air and dust intake on the polishing machine be completely blocked off with a piece of cardboard when using this disc as sparks can be produced which will set the cotton lint and dust in the filters on fire. This is a very real danger of fire with such flying sparks-I’ve seen it happen twice.
If one places a polishing compound such as tripoli or Fabulustre® onto the smooth paper side of the disc then one has an extremely fine polishing lap that can produce superb flat surfaces on jewellery with plane surfaces. If one makes a traditional type disc one can rubber cement a piece of linen writing paper onto the paper side for an even smoother polishing effect. It is far superior in flat finishing to expensive hard felt buffs that jewellers use. Plain paper would probably work well for polishing. Several discs with different starting grits are useful. For a minimum cost and preparation time this type of disc sander and .i.polishing lap; offers a great deal.