1 year, 9 months ago-
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Hello USFG Members
I have only joined today.
I have been reading a couple of articles about Mast Flex and I am rather intrigued by this.
I am at a loss to see how the mast can flex. Most masts that I have seen are at least diameter 22mm and approximately 300 mm high. The Main Body of the machine does go up that far so the maximum height at the centre of that component would be 250 mm at the most. What is the material from which the masts are manufactured?
Over the top of the mast is a bushed sliding tube. Againg what Material and its thickness etc.
The workpiece in some cases is approx. 150 mm. Without doing any calculations, there is plenty of room for error from the centre line of the mast to the stone being faceted if there is excessive force applied to the stone.
Could someone , please shine some light on this .
Thank you.
Kind Regards
Ian ORRELL
“Flex” depends on what is tolerable. At Boston’s Museum of Science is a piece of railroad track, to which is attached a strain gauge with a big meter. Children amuse themselves by “bending” the track, perhaps by a few millionths.
When we are polishing to a perfect meet, we are working in the order of microns. Those XS3 machines I used to build had a mast made of 3/4″ 400 series stainless steel casehardened to Rockwell C 60 or so. I can flex that mast if I try.Masts with bushed sliding tubes cannot have zero-clearance or the tube would not move. This clearance is probably interpreted as mast flex. A solution would be a very expensive two-axis ball bushing.
It depends on the design as well. Masts that are built up from smaller sections illustrate the difference between a “Structure” and a “Mechanism”.
Ideally, we are not using those forces in faceting, but some people are heavy-handed, or are in a hurry.
what machine brand is it your talking about??? yes i’ve seen some that do have flex thats why when asked my preference i say ultra tec first i’ve not had mast flex on that machine and the raytech which doesn’t have a mast. mike z. gemmakermz@cs.com
You might take a look at the “Beale/Woolley Depth of Cut Indictor” for some more thoughts. For some applications, mast flex can be a tool rather than a problem.
Mast flex is avoided if you cut with pressure on the stone itself. Hold the stone, not the quill.
I have trouble with depth of cut. I have studied articles on Beale-Woolley depth of cut indicator, but have never been able to figure out
how to set one up on my Facetron. Not able to make out exactly where to make connections, etc.Dave Woolley may have more advice, but look at the article “Art Kavan’s Facetron Installation” in the Library -> Article Archive
Keith,
It took me a year to accomplish attaching an Ohmmeter to a Facetron. I had to open the “black box” and do a lot of tinkering inside; not recommended. In use, the Ohmmeter needle wobbled a lot. The Tube on Mast bearing was the source of the wobble. I gave up when I realized my hand was causing the bearing to wobble, even though I could not feel it. One would have to place some kind of roller bearings between the mast and the tube to over come the wobble. Also not recommended.
I suggest you use the Facetron as designed. Add the dial indicator if your does not already have one. It is a fine machine and you will grow accustomed to the slight hand pressure that keeps the tube to one side of the wobble.
Best regards,
Dave Woolley”when it comes down to it they ALL have some flex as said before if it can slide there is a tolerance play. i have to amend a early statement i made above but theres always play because of hand pressure, no stopping that. i’ve cut on most machines and it can always happen. through time you’ll recognize this and watch closer what your doing.
I believe that the spring in the “new” Dial Indicator applies the same pressure from one “identical” facet to the next in a tier. This loads the ‘mast bend’ and loads on any involved bearing the same amount. A major improvement in my opinion.
The mast is only half of your machine, the platen is spun between two bearings. Every moving part of the faceting machine is going to have some slack. The trick is to let the machine do it’s work, don’t force your cut. Use the best magnification you can afford, and just learn when to stop cutting. When your machine develops too much slack, you will have to give it a tune up. New bearings or index gears.
This is my first post/reply because I too am new here.
I have a Graves Mk 1 faceting machine and I can assure you, it definitely has some flex to the quill.
I don’t know how much it will flex because I don’t force it … much.
But since the vernier scale is in degrees and there are no .25, .5 or .75 degree marks, I have to guess and utilize both the Fine Height Adjustment and/or a little bit of “English” on the quill to make my Meets meet. That is to say, I utilize the flex to a small degree.
BTW my quill assembly is 10.55mm in diameter !Year ago I watched Mike Watkins at Emerald Hollow Mine, Hiddenite, N.C., rapidly facet with an ancient Graves. The bearing were so loose and sloppy that I could not believe it! I was expounding the benefits of an Ohmmeter and he was countering with a demonstration of his cutting technique. For all practical purposes, he was hand faceting with the Index gear and protractor being just a rough guide. Kind of like an early unrefined Jamb Peg machine. Remember, he faceted 8 to 10 hours a day cutting stones his customers found in the sluices. He had developed exquisite hand control and twisted and forced the machine as needed. He also cut very fine gems when he had a mind to do so, probably on another brand machine at his house. His offer to cut one of the very large NC emeralds from Hiddenite was turned down. His yield was calculated to be very slightly less than what was cut but his gem would not have been a “fish eye” that now sadly is on display. Mike also won a large Las Vegas bet; he bet that he could finish is signature scissors cut in less that an hour. . . a feat he had accomplished with his sloppy Graves, many times in his shop. It is not the price of the machine, the latest gadgets, or the finest bearings that ultimately make the difference. It is the practice and skill one develops as we master the imperfection of our machines. Of course one can be diligent and correct mechanical problems as they are identified, and add an Ohmmeter and make a bio feedback machine . . .
dave yup the whole thing comes down to YOU to do the faceting, the machine is just a tool for holding and guiding. use your eyes. the machine can set angle and index but how far you cut, i haven’t found any machine with an absolute stop where everything meets exact. in 68-77 while working at crystalite i was a a big show in Wa. D.C. where a woman won the faceting trophy, the stone was accurate and beautiful and she was totally blind. figue that one out. it wan’t the stops.
gemmakermz@cs.com
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