A flat lap is a horizontal spinning disk to grind and polish flat surfaces onto the fired glass piece.
Many desire one of these but are put off by the expense and sometimes the space they occupy.
There is a do-it-yourself alternative that I have used.
This is to use potter’s wheels as flat laps. Table top versions are useful as they are moveable to a storage shelf when not in use. Mine was kept on a shelf until it was taken outdoors to avoid water spray indoors. They do require some adaptations and have limitations. But the great advantage is lower cost.
There are new table top ones available from £135 with a 25cm/8” turntable. This is the maximum size. They often come up second hand on ceramic and local buy and sell sites for even less.
Adaptations are required. These include:
The wheel is surface is aluminium, so a magnetic surface must be applied, as the metal discs rely on magnetic attraction to stay in place. Magnetised sheets with self adhesive backing are available to be cut and stuck to the wheel.
A water supply needs to be fixed. This can be a removable reservoir with an adjustable flow valve, or a hose from the standard water supply with a controlled flow.
The water catchment basin around the wheel does not have a drain. You can live with that and interrupt the work to empty the basin as required. Alternatively, a hole can be drilled in the basin and a Loc Line or similar system can be fixed to drain into a bucket. The waste water should not go into a drain, because the sediment will eventually block it solid. A recirculating pump is also a bad idea, because it will distribute glass grit along with the water onto the disc, and cause scratches when using a finer grit disc.
Discs must be acquired. Consider metal discs with a progressive range of grits from around 50, and doubling the grit number (halving the grit size) to around 400. I normally start with a 100 grit disc, as the coarser grits are really only for removing large amounts of glass. 100 grit can do the same job as 50 grit, but requires longer.
Inexpensive steel disks are available. However the quality of grit sizing is not always accurate, making the use of the cheaper discs with grits above 220 inadvisable. The finer grits and smoothing pads need to be of a higher quality and their expense will be justified by the lack of gouges in the later stages of fine grinding and polishing.
If you use larger or smaller discs than the wheel, you need to mark the centre on the magnetic pad, to be able to easily centre those smaller or larger discs. Of course, the smoothing and polishing pads are on flexible backings and cannot be larger than the wheel. Only the steel backed discs can be larger.
This picture is an example of my potters wheel adapted as a flat lap. The magnetic pad has been attached to the wheel, and the water supply hose and flow valve are also attached.
Limitations
There are limitations to this make over of course.
The wheel surface is 25cm/8” dia. A steel plate could be attached to make the surface 30cm/12”, although centring it may be difficult.
The speed is easily adjustable, but the top speed is around 300rpm
The the basin is 32cm/13” diameter and its edges rise above the wheel, limiting the size of items that can be worked.
There is no drain from the surrounding waste water basin, so drain holes may need to be added.
In spite of the limitations, this worked well for me for several years, until I had the need to flat lap large numbers of items. For those with moderate lapping needs, this is a good, low cost piece of equipment.
