Using a flat Lap

[tinker]

Hi all,
        I have just became the benefactor of a 10" Steel Lap Machine,  although I have been cabbing for many years, I have never used a flat lap.  What I intend to do with this machine is to polish slices of agate, jasper etc.   I know someone on the forum can answer this question, do I apply the grits to to steel lap with water or do in need to purchase grit discs to polish.

Help

Tinker

[mehoose]

Hmm, not sure, didn't take much notice at the old club sorry. What I did notice was that they made rings out of a plastic aggy pipe or some such to keep the stones protected from wacking into each other.... also, I think they had a piece of carpet to lay in it for the final polish. Oh and it had to be really cleaned between grits.

[Aussie Sapphire]

The Gyroc Model A tumbler comes with a lapping plate which is also 10".

The instructions for that one are here:
http://www.aussiesapphire.com.au/storage/GyrocA-FlatLap.pdf

Maybe you could read those as a starting point.

Mehoose is right - absolutely thorough cleaning between grits and then use a felt pad (which seems like coarse carpeting) for polishing.  The rubber/plastic tubing around the edge stops the rocks banging into the side of the steel pan.




cheers
Leah

[tinker]

Thanks Guys for the ideas, I will have a go at the old carpets, mehoose do you know what grit they used.

[mehoose]

I think it would have been Cerium for final polish on most. Is that what people tend to get Leah? I'm thinking for the agates , woods, jaspers.
The alox will go into cracks and leave horrid white lines, it tends to go in whereas the cerium doesn't.

[FlashGP]

Is the flat lap a rotating or vibrating disk?

If a rotating disk I've used one at the club to flatten the back of my stones before prepolishing and polishing.  Ours is about an 20 inch cast iron flat lap.  We use carborundum grits and drip water onto the lap.  After use it needs cleaning and oiling.  You need to hold the stones or they spin off. 

We have a separate felt flat lap for polishing slab.

[Jimnyjerry]

If it is a spinning flat lap, give the surface a lite spray of water from a spray bottle then sprinkle some 1200 grit (the sort you would use in a rock tumbler) over the surface, use your rock slab to rub it into a tin paste over the surface.

Use a bit of aluminium wire to mark the slab surface to be polished with a cross hatch pattern then you are ready to hold the slab on the lap and turn it on.

Should hear a chh sound as the grit cuts the slab.  If the lapgrabs the slab too hard spray a mist of water on it.  If the lap is too wet add a bit more grit.

Flat lapping a slab can take a long time depending on the material.  When you wash your slab after time on the lap you will see how the cutting is going by the amount of cross hatching remaining on the slab.

As FlashGP said the final polish with tin oxide is done on a different machine with a spinning leather cover.