Save your grinding disk and possibly valuable material.. This is for large stones  that would take a long time to shape .Works with a 6 inch saw blade or smaller if you are using a 6 inch faceting machine. Thin blades will possibly warp if you are not careful. I used a 0.50mm blade for mine. If you need to use a 1/2 inch drill bit to slightly enlarge  the hole for the blade you will need to do so for the adapters too.  My Facetron needed that done but an older Graves Mark 1 and a friend’s Chinese machine did not. 
You have to dop the stone you wish to saw. If you try holding it by hand you probably will ruin the blade, the rough, and your fingers. With the machine switched off, set the protractor at the angle you wish to cut. Then lower the mast with the stone between the edge of the saw and the splash pan until the saw is at the level at which you wish to make the cut. Make sure that the stone will be trailing so that if it jams on the saw it will be knocked away from the blade. Then swing the stone away from the saw, run a copious water stream onto the blade, switch on the machine to run at full speed, and again make sure that the stone will be trailing. If you can, run the saw blade counter-clockwise so that if the stone flies off the dop it flies away from you. Very gently feed the stone into the saw blade, taking care not to flex the thin blade. Allow the diamonds in the blade to do the work. Do not force the stone onto the blade. Use just enough finger pressure to keep the blade cutting the stone. Swing the stone gently off the blade intermittently to allow water to flush the cut and reach the underside of the saw blade. Feed it back in carefully, allowing the blade to find the groove. Throughout, this is a delicate, unhurried operation.
Why would you want to do this? Setting the protractor at your pavilion mains angle means you can preform the bottom of a big stone very quickly, saving your coarse lap from wear, and possibly saving workable pieces of rough to cut smaller stones with. Using the 45 degree adapter enables you to section long crystals very accurately or to cut thin slices.

Print 2 of this. Mine was printed in PLA.