Australian Facetors' Guild Limited

GIRDLE CREEP FINALLY SOLVED!

  • 30 Apr 2018 3:05 PM
    Message # 6125725
    Anonymous

    For along while now "Girdle Creep" or uneven girdle has been constant issue. And for many in the world of faceting it has been the bane of their existence also. After reading a article in "Facet Talk 220" about Orientation of Crown and Pavilion Factes by Paul Sabolta. A very good article and well worth a read. Paul mentions that often the cutter blames a problem in the transfer. And I for one have also blamed the transfer in the past. Having gone down the path of checking that all was good with using a "D Dop" to check that the base plate was level and zeroing the cheater or "sighting in the rifle" the "Girdle Creep" still managed to take center stage on the transfer. Although Paul uses a different approach by mentioning that the first four facets must be cut to exactly the same depth without changing any mast height settings. In his approach the first four facets are cut in opposites to create a centre point.  However, I'm going to take a different approach to this problem. In the past I would also cut opposite facets to a centre point, which is not a bad method. These days I'm more likely just to cut facets in a continuous order. In a recent project I cut a stone with a 32 facet girdle on a 64 index wheel. So the order of the facets where 64-2-4-6-8-10 etc. So after cutting the pavilion and transferring to cut the crown, normally I would suffer "Girdle Creep" by cutting the same indexes. So in this case the first cut was index 64,  and by the time I went around to index 62 that rotten uneven girdle would rear it's ugly head. So the first facet you cut ( in my case index 64) has to cut to perfect depth in relation to your desired girdle width. Once you have established that this first cut is to the required depth, then all other girdle facets should match? Well you would think they would, but this is not always the case. The key is never adjust the height of the mast as you go through the index rotations while cutting the girdle. And I mean never!  Cut your first facet to the required depth (remember this facet index) with your mast set at zero, lower the mast by no more than a third of one millimeter and leave it there. As you go around you will need to use feel and pressure on some of facets. You will find that the girdle should be level and accurate. Sometimes you may have to do another rotation, but leave that mast alone. If you find that the girdle is too thick for your liking, repeat the same method. But you must start from the first facet as you did before. I usually lower the mast less while cutting each girdle rotation. There is nothing worse than overcooking a girdle by making it too thin. Regards Cliff

    Last modified: 30 Apr 2018 4:36 PM | Anonymous

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