Australian Facetors' Guild Limited

Wendy depending on the length to width of the stone will show what cam you need. Gemmasta cams were made with the difference between length  and width. i.e. a cam marked 2 would preform a stone with a difference of 2mm a 10x8, 22x20. A cam marked 3 will cut 10x7,18x15 and so on.

I do know that Matt Young at VJ Faceting Machines is doing a lot of work machining parts for Gemmasta machines.  You could look him up and talk to him via phone.

Re cams

The only exception to the last reply is that only Hall cams can be used on a Hall pre former as this unit is a variable ratio cam i.e. for the oval cam the cam follower position is varied to change the size of the stone.  It must be noted that Hall cams are "skinnier" than Gemmasta cams so a cut that suits say the Gemmasta unit will produce a "fatter" cut i.e. the intermediate mains are more prominent than those cut from a Hall unit.  The Hall oval cam has a ratio of 0.666 to 1, so if you have say a stone that will clean up at 10mm on the long axis the width will be:     10 x 0.666 = 6.66 wide.  We are not going to work to 2 decimal places so call it 6.7mm.  The Hall variable ratio preformer  had cams for oval, pendeloque, marquis, tripolar and pear shapes.