Flat Laps for Lapidary Shops

Perhaps the easiest flat lap that can be built is from a double headed floor-scrubber machine that can be found in many thrift stores and flea markets. Almost total de-construction has to transpire, meaning you have to take it apart down to the motor level, while leaving the rotating heads in place. Then you must build a wooden or metal case for it so that both heads sit flat and will run freely when power is applied. It is best to incorporate plastic or wooden sidewalls to this box for safetys sake. No matter how hard you try, eventually a wheel will “Fling” a stone, and its better if it doesn’t fling it across the room.
Also, all wheels will throw an amount of abrasive due to centrifugal force, because water is usually mixed with said abrasive to create a slurry. See the section on abrasion and application at the end of this book for more information on that. To make good sidewalls for your flat lap, either build wooden edges all the way around the wheel, above the level of the wheel face, or cut the bottom out of a plastic pan or box, leaving enough of the bottom around the edges to use as bolt-down. Set the pan or box over the wheel, then screw down to whatever kind of baseboard you have constructed. Metal sidewalls are not advisable, because they may rust or be too sharp for safetys sake, and because if you throw a nice stone against it with force, as the wheel will often do, it will sometimes break the stone. Finally, plastic can be holed easily with heat, like a nail that has been heated up with a lighter. Hold the nail with pliers of course.
The floor-scrubber flat-lap wheels usually run counter to each other, as far as direction is concerned. One runs to the left, the other to the right. Not really a problem but something to be aware of. The nice thing about these floor scrubber flat laps is that the wheels/shafts are usually socketed and locked by means of a twist/pin system, meaning you set the wheel on the shaft according to the pin layout, then twist the wheel and it locks. Also, most times the wheels themselves can be had cheaply at any hardware, and no special equipment or mounting hardware is necessary to make this configuration efficient and profitable. Just remove the brushes, and screw on some plywood disks. Voila, theres the laps. On disks I always put a layer of neoprene rubber, divers wetsuit material, with the textured side up. To this I adhere my polishing pad or abrasive disk. Worx well. This lap can also be adapted/modified for faceting, most notably the jamb peg type of faceting.
The other type of flat lap which I use is almost as simple, and was put together in a couple of hours. Like my diamond saw, this flat lap makes use of a shaft bearing/spindle assembly from a rider lawnmower (see diagram above).

Instead of mounting vertically for a blade I mount this horizontally for a flat lap, Simple. Other parts for the project are a pulley belt, a motor, and some scrap lumber. I use a piece of plywood over a two-by-four frame to mount this flat lap configuration, with the two by fours on edge so there is about a 4” clearance from workbench surface to top of flat lap. This supplies clearance for the pulley and motor works underneath. I drill holes in the plywood to mount the bearing with the shaft pointing upward, and the pulley below the plywood. Then I mount the motor off to the side, with its pulleyed-shaft protruding BELOW the plywood table, lined up with the pulley. It may be necessary to put the motors shaft through a drilled hole, mount the motor permanent, THEN apply the pulley to the motors shaft below the top of the wooden frame box. I use a 1725 RPM heater motor and it was real easy to mount because it has a mounting plate on the front. I made the hole of one of these mounting screws elongated, so I could easily adjust the tension on the pulley belt by loosening that bolt, and pulling it tight. I cut out the bottom of a rectangular plastic box and fitted it over the protruding shaft of the lawnmower bearing, so that when my wheel was mounted on the shaft there was plenty of clearance but good high side walls. The nice thing about the lawnmower bearing is its shaft is usually threaded (Get one thats threaded!) and the mounting of the wooden or metal wheel only requires it to be center bored in the diameter of the shaft. Then the wood disk can easily be mounted with a couple washers on each side of the disk, and a nut that threads onto the shaft.