Forums Beginner Questions Faceting Machine Mast Flex


7 replies, 6 voices Last updated by Alan Balmer 3 years, 6 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


    Jon Rolfe
    @jonathan lrolfe

    “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.



    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.


    Alan Balmer

    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.


    Alan Balmer

    Dave Woolley may have more advice, but look at the article “Art Kavan’s Facetron Installation” in the Library -> Article Archive


    Alan Balmer


    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”

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