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.

Latest Beads

The diamond core bits on ebay are real cheap from china and some work well.  I used them to punch these beads out and drilled the holes by eye, some you can tell, some not.  The material is stuff I collected in Hachita.  I then used pins in small pin vises to hold the bead against a vertical 6" diamond flat from Lopackis rotating at about 600 rpm to rough them in and homemade sanding wheels of the flap design to sand down to level where I could finish with diamond powders.  See his bead tutorial at lopacki.com for information on how the bead works.  The bottom pix is before polish at about 200 grit sanding level....b

Polishing Pad

One of the things covered lightly in the book but could use more attention is how to obtain good polishing pad, for use on the flat lap with slurrys and powders.  I know people who use silica powder as polish and apply it with carpeting, both shag, and of the indoor outdoor variety.  I have used their equipment and it works, but slings more than is necessary because the silica is cheap cheap stuff and the mechanics are not worried about it.  When using expensive abrasives like cerium oxide, it is best to keep from slinging anything, although that can only be achieved in degrees, never perfectly.

I like some of the new fabrics and most can be found in cloth stores or hobby stores that cater to sewing.  I have tried several different types of thicker wooly cloths at these places and like them, also marine upholstery, if heavy enough, works wells sometimes, if its the right type.  Experimentation with different types of materials, especially salvaged stuff, is encouraged.

I found the best polishing pad for my purposes to be school bus seat upholstery, fire retardant, with a good rubber/plastic exterior, that is the down side of the pad, where it gets glued to the lap plate, and a real durable fluffy padding on the inside, which is what you polish on.  It can be obtained as salvage at junkyards.

I am soon to be experimenting with floor liner out of a newer car, it is a somewhat woven and pressed 1/4" thick pad which may or may not be good for polishing, I will report it.  This is the pad that goes between the carpet and the floor of a car or suv.  It looks like it might be better than most things.

***** IT WAS NOT.  It tore up quickly, disintegrating almost as fast as the earlier polishing pads they used to sell mje at the rock shops, no longevity whatsoever.  Back to the drawing board, my best stuff yet is fireproof upholstery out of school bus seats.

The bottom line is the polishing pad is necessity, and it wears out, it must be replenished.  If you find a material that works for you, and you are doing a lot of work, or anticipate doing a lot of work, get a good supply if you can.